Clinicopathological variables predicting progression of azotemia in cats with chronic kidney disease

Efficacy of oral AB070597 for the management of chronic kidney disease in cats: a prospective, randomised, controlled parallel-group study

OBJECTIVES

It has been reported that AB070597, which contains amino acids and peptides, may prevent the progression of chronic kidney disease (CKD) in cats. The aim of this study was to evaluate the effect of AB070597 on CKD in International Renal Interest Society (IRIS) stage 2 or 3 cats compared with a placebo.

METHODS

A prospective, randomised, controlled parallel-group study was conducted on 35 cats with CKD. The cats were randomly allocated to receive 300 mg of AB070597 or placebo for 180 days, and cats were re-examined every 30 days. Changes in the results were compared from baseline to endpoint in each group, and the efficacy of AB070597 in cats with CKD was assessed.

RESULTS

A total of 35 cats met the inclusion criteria, of which 20 received AB070597 and 15 received a placebo. Blood urea nitrogen (BUN), creatinine (Cre) and phosphorus levels increased significantly in the placebo group at 180 days compared with those at baseline, 30 days and 60 days, whereas these values were not significantly changed in the AB070597 group during the study period. The IRIS stage was also stable in cats with AB070597 from the baseline to the end of the study, whereas the IRIS stage progressed from stage 2 to stage 3 in 26% of cats with placebo. Body weight did not change significantly in either group.

CONCLUSIONS AND RELEVANCE

The administration of AB070597 in cats with CKD may be effective in preventing CKD progression.

Comparison of serum creatinine, point-of-care symmetric dimethylarginine and renal imaging with glomerular filtration rate measured by renal scintigraphy in healthy and early chronic kidney diseased cats

The aim of this study was to evaluate routinely used tests to diagnose cats in early stages of chronic kidney disease (CKD) and to describe a model for evaluating these variables simultaneously. Apparently healthy cats were screened using serum creatinine (sCr), point-of-care symmetric dimethylarginine (POC SDMA), urinalysis, urine protein/creatinine ratio (UPC) and imaging evaluation. Those parameters were compared to glomerular filtration rate (GFR) assessed by renal scintigraphy. Forty-four cats were included and consisted of 14 (31.8%) healthy cats (absence of abnormalities in renal morphology and sCr less than 1.6 mg/dL), 20 (45.5%) cats classified as CKD I (presence of abnormalities in renal morphology and sCr less than 1.6 mg/dL) and ten (22.7%) as CKD II (sCr equal to or greater than 1.6 mg/dL, with or without abnormalities in renal morphology). A large number (40.9%) of apparently healthy cats presented reduction in GFR, which included half of CKD I patients. Point-of-care SDMA was not a good predictor for decreased GFR, nor was it correlated with the variables GFR and sCr. Glomerular filtration rate was significantly lower in CKD I and II groups in comparison with healthy cats, but there was no significant difference between the CKD I and II groups. Multivariate logistic regression model identified three variables that affected the odds of a cat having decreased GFR (< 2.5 mL/min/kg): sCr (OR = 18.3; p = 0.019; CI = 1.6-207.2), and the ultrasonographic findings 'reduced corticomedullary definition' (OR = 19.9; p = 0.022; CI = 1.6-254.0) and 'irregular contour' (OR = 65.6; p = 0.003; CI = 4.2-1038.2). Renal ultrasonography evaluation should always be considered for screening early CKD in apparently healthy cats.

Adeno-associated virus-vectored erythropoietin gene therapy for anemia in cats with chronic kidney disease

BACKGROUND

A treatment of chronic kidney disease (CKD)-associated anemia in cats is needed. SB-001 is an adeno-associated virus-vectored (AAV)-based gene therapeutic agent that is administered intramuscularly, causing the expression of feline erythropoietin.

HYPOTHESIS/OBJECTIVE

We hypothesized that SB-001 injection would lead to a sustained increase in PCV in cats with CKD-associated anemia.

ANIMALS

Twenty-three cats with International Renal Interest Society (IRIS) Stage 2 to 4 CKD-associated anemia were enrolled at 4 veterinary clinics.

METHODS

In a prospective clinical trial, cats were treated with 1 of 3 regimens of SB-001 (Lo 1.2 × 109 genome copies [GCs] on Day 0; Lo ± Hi [supplemental 2nd dose of 3.65 × 109 GC on Day 42]; Hi 3.65 × 109 GC IM on Day 0) and followed for 70 days.

RESULTS

A response to SB-001 at any time between Day 28 and Day 70 was seen in 86% (95% confidence interval 65, 97%) of all cats. There was a significant (P < .003) increase in PCV from Day 0 to Day 28 (mean increase 6 ± 6 percentage points [pp]; n = 21), Day 42 (8 ± 9 pp; n = 21), Day 56 (10 ± 11 pp; n = 17), and Day 70 (13 ± 14 pp, n = 14). Twelve cats were hypertensive at baseline, 4 of which developed encephalopathy during the study. An additional 6 cats became hypertensive during the study.

CONCLUSIONS AND CLINICAL IMPORTANCE

Results of this study suggest that SB-001 therapy represents a suitable single injection treatment that can address nonregenerative anemia in cats with CKD. It was generally well tolerated; however, hypertension and encephalopathy developed in some cats as previously described in association with erythropoiesis-stimulating agent therapy.

Determination of age-specific reference intervals for selected serum and urinary biomarkers in elderly cats

OBJECTIVES

Annual health screening is recommended in elderly cats to allow the early detection of conditions such as chronic kidney disease (CKD) and hyperthyroidism. Nevertheless, age-specific reference intervals (RIs) for renal and thyroid parameters in this population are lacking. The aim of this study was to determine age-specific RIs for selected serum and urine biomarkers related to CKD and hyperthyroidism, namely serum creatinine (sCr), symmetric dimethylarginine (SDMA), phosphate (P), total calcium (tCa), total thyroxine (TT4), urinary protein:creatinine ratio (UPC) and urine specific gravity (USG). These RIs were established for elderly cats (aged ⩾7 years) in general, as well as for mature adult cats (aged 7-10 years) and senior cats (aged >10 years) separately.

METHODS

A prospective study was conducted on client-owned cats aged ⩾7 years and considered healthy by their owners. The cats were screened to rule out metabolic and systemic diseases by means of a thorough history, complete physical examination, blood examination and urinalysis. The data from 206 healthy elderly cats (134 mature adult and 72 senior cats) were included. Age-appropriate RIs were determined following the guidelines of the American Society of Veterinary Clinical Pathology and compared with existing laboratory RIs.

RESULTS

Clinically relevant differences between the age-specific RI and the laboratory RI were found for several variables. Compared with the laboratory RI, the upper limit of the RI for cats aged ⩾7 years was lower for sCr, TT4 and P, and higher for SDMA. The lower limit of the age-appropriate RI was lower for USG. The new RI was almost identical to the existing laboratory RI for tCa and UPC.

CONCLUSIONS AND RELEVANCE

Using age-specific RIs for renal and thyroid biomarkers in mature adult and senior cats has important clinical consequences for the interpretation of health screening results in elderly cats. This confirms the need to adapt laboratory RIs to the specific animal population for which the RI will be used.

Beraprost and Overall Survival in Cats with Chronic Kidney Disease

BACKGROUND

Overall survival is the most important outcome for treatment response in feline chronic kidney disease (CKD). Beraprost has been shown to reduce the kidney function decline in cats with International Renal Interest Society (IRIS) stage 2 and 3 CKD. However, the association with prolonged survival has not yet been examined.

OBJECTIVE

To assess the relationship between beraprost and overall survival in cats with CKD in real clinical practice.

ANIMALS

Client-owned cats with IRIS stage 3 CKD (n = 134) were evaluated between 2017 and 2020.

METHODS

A retrospective cohort study based on data from electronic medical records of one hospital.

RESULTS

The cohort was divided into "beraprost therapy" and "no beraprost therapy" groups, and survival analyses revealed that overall survival was significantly longer in the beraprost therapy group, using Kaplan-Meier curves (p = 0.004). However, baseline phosphate is known to be an important prognostic indicator and was not well balanced between the two groups. Therefore, a subcohort of 97 cats was selected (those having baseline phosphate <6.0 mg/dL) that allowed for this parameter to be balanced between groups. The survival data in this subcohort were consistent with those of the overall study cohort.

CONCLUSIONS

In feline patients with CKD, beraprost therapy is associated with better overall survival.

Therapeutics of managing reduced red cell mass associated with chronic kidney disease - Is there a case for earlier intervention?

Reduced red cell mass is a poor prognostic indicator in chronic kidney disease (CKD) patients. Whilst overt anaemia impacts on the quality of life of patients with CKD, lowered red cell mass may also compromise oxygen delivery to proximal tubular cells and contribute to progressive kidney injury. Epidemiological data from cats with CKD support this hypothesis although controlled interventional studies involving drugs that raise red cell mass in trials designed to test this hypothesis are lacking in both human and veterinary medicine. Recombinant analogues of erythropoietin (EPO) are currently standard of care for human CKD patients where low red cell mass impacts on their quality of life. Resistance to EPO is encountered in 20% to 40% of patients treated, probably due to functional iron deficiency, reflecting the difficulties of managing iron deficiency associated with the chronic inflammation of CKD. Similar issues are likely faced in managing anaemia in feline CKD although published data on the use of human EPO analogues are limited as such treatment in cats risks antibody formation resulting in red cell aplasia and transfusion dependency and so is reserved for late stage cases only. This article reviews the recent alternative therapeutic approach to increase red cell mass using HIF-prolyl hydroxylase inhibitors and explains their mode of action and theoretical advantages over EPO analogues in the context of iron metabolism. The results of human clinical trials and the potential benefit of adopting this approach in feline CKD patients are discussed.

Diabetes Mellitus and the Kidneys

The pathomechanisms implicated in diabetic kidney disease in people are present in dogs and cats and, in theory, could lead to renal complications in companion animals with long-standing diabetes mellitus. However, these renal complications develop during a long period, and there is little to no clinical evidence that they could lead to chronic kidney disease in companion animals.

Evaluation of Bcl-2 as a marker for chronic kidney disease prediction in cats

Chronic kidney disease (CKD) is a frequent condition in elderly cats. Bcl-2 is linked to kidney disease through the processes of apoptosis and fibrosis. The purpose of this study is to examine Bcl-2 levels in CKD and clinically healthy age-matched cats in order to evaluate the relationship between Bcl-2 levels, signalment, and blood parameters in cats with CKD. The circulating levels of Bcl-2 were determined using an immunoassay in twenty-four CKD cats and eleven clinically healthy age-matched cats by the utilization of the general linear model (GLM), Pearson correlation, principal component analysis (PCA), ROC curves, the Cox hazard model, and Kaplan-Meier survival analysis. These were all conducted in order to explore Bcl-2 levels and their connection with other variables. The Bcl-2 immunohistochemical intensity was graded in each glomerulus and tubulointerstitium. McNemar's test was performed in order to compare the expression of Bcl-2 in the two renal tissue sites. The circulating Bcl-2 of CKD cats was significantly lower than those of clinically healthy age-matched cats (P = 0.034). The presence of circulating Bcl-2 (P < 0.01) and the severity of CKD (P = 0.02) were both linked with the survival time of cats with CKD. The area under the curve (AUC) of Bcl-2 for detection of CKD was 0.723. In cats, decreased circulating Bcl-2 was associated with increased blood BUN, creatinine levels, and CKD severity. Bcl-2 protein expression was reduced in the renal tissues of CKD cats as the disease progressed, resulting in a decrease in their survival time. This study demonstrated that Bcl-2 may be effective in diagnosing feline CKD.

Body Composition of Healthy Cats and Cats with Chronic Kidney Disease Fed on a Dry Diet Low in Phosphorus with Maintenance Protein

The aim was to evaluate the effect of feeding a low-phosphorus and maintenance protein diet in healthy cats and cats with chronic kidney disease (CKD) with IRIS stages 1 (CKD-1) and 2 (CKD-2). Cats were initially fed a senior diet (30 days) followed by the renal diet (60 days). Body composition, body weight (BW), muscle mass score (MMS), and body condition score (BCS) were assessed before (T30) and after renal diet intake (T60). General mixed linear models were used to assess the effects of fixed groups and moments (T30 × T60), as well as their interaction, in addition to the random effects of animals within each group. Unlike healthy cats and cats with CKD-1, cats with CKD-2 had a loss of BW, lower BCS (p < 0.005), and lower MMS (p = 0.0008) after 60 days of consuming the renal diet. The fat mass and lean body mass (LBM), determined by the deuterium isotopes method, did not change in all cats between T0 and T60. In healthy cats and cats with CKD-1, the renal diet resulted in maintenance of BW, BCS and MMS; but cats with CKD-2 presented lower BCS and did not reduce phosphatemia after consumption.

Urinary Protein/Creatinine Ratio in Feline Medicine: Reasons to Perform It and Its Role in Clinical Practice-A Retrospective Study

This study aimed at understanding the reasons veterinarians conduct a urinary protein/creatinine ratio (UPCR) in cats, correlating it with signalment, dipstick proteinuria tests, and urine specific gravity (USG) and assessing its role in chronic kidney disease (CKD) diagnosis and monitoring. A retrospective study was conducted, including medical data from cats consulted between 2016 and 2018 in a veterinary teaching hospital and submitted to at least one UPCR measurement. A total of 140 cats were included: 35% non-proteinuric (UPCR < 0.2), 25% borderline proteinuric (0.2 < UPCR < 0.4), and 40% overtly proteinuric (UPCR > 0.4). In contrast to other studies, there was no association between UPCR and male reproductive status. UPCR was mainly requested for CKD diagnosis and monitoring. Correlation between UPCR and combined results from dipstick tests and USG was low and inconsistent. Proteinuric CKD cats had a worse outcome at both 6 (odds ratio (OR 4.04) and 12 months (OR 4.36)), and this finding was more pronounced for severely proteinuric cases in which the OR for death was 4.36 and 6.00 at 6 and at 12 months, respectively. In addition to reinforcing the negative prognostic value of proteinuria, this study stresses the low and the inconsistent agreement between UPCR and the combined results of dipstick tests and USG in cats.

Does intravenous contrast medium administration result in altered renal biomarkers? A study in clinically stable cats with and without azotemia

OBJECTIVES

The aim of this study was to determine the prevalence of post-contrast acute kidney injury or comparable side effects on kidney function in cats receiving the non-ionic, iodinated agent ioversol and/or paramagnetic agent gadoteric acid.

METHODS

Fifty-two animals were divided into four groups on the basis of contrast medium administration for imaging: ioversol (n = 27), gadoteric acid (n = 12), dual contrast media (n = 4) or control, which received an infusion of isotone intravenous fluids only during anaesthesia (n = 9). Blood and urine samples were obtained three times after contrast administration and compared with values obtained prior to administration of the contrast medium. Creatinine (<1.60 mg/dl), symmetric dimethylarginine (SDMA; ⩽14 μg/dl), urine protein:creatinine ratio (UPC; <0.2) and critical differences for creatinine (<0.3 mg/dl) and SDMA (<5.98 μg/dl) were measured.

RESULTS

No significant short-term effects on mean creatinine, SDMA and UPC measurements were seen. Borderline proteinuria (UPC, 0.2-0.4) was detected in 11.4% of cases after contrast media administration. A UPC of more than 0.2 in five cases indicated that contrast media may affect kidney function, leading to (transient) proteinuria.

CONCLUSIONS AND RELEVANCE

This study found no side effect on renal function following the administration of ioversol or gadoteric acid, provided patients were adequately hydrated. However, the clinical relevance of proteinuria in some cats needs to be evaluated in future studies.

Immunohistochemical Expression of TGF-β1 in Kidneys of Cats with Chronic Kidney Disease

Transforming growth factor-beta 1 (TGF-β1) plays a central role in the progression of chronic kidney disease (CKD). However, in feline CKD, renal expression of TGF-β1 and how it changes as the disease progresses have not been fully studied. In the present study, we immunohistochemically assessed the renal expression levels of TGF-β1 in cats with CKD and statistically analyzed its correlation with CKD severity. Clear immunosignals were detected in the glomerular mesangial cells, Bowman’s capsules, proximal tubules, distal nephrons, platelets, and vascular smooth muscles in the kidneys of cats with CKD. Statistically, luminal signals in the distal nephrons showed positive correlations with plasma creatinine levels and glomerulosclerosis, while those in the proximal tubules and platelets showed negative correlations with plasma urea and/or creatinine levels. Therefore, it was suggested that the changes in the renal expression of TGF-β1 could be associated with progression of feline CKD.

Renal biomarkers in cats: A review of the current status in chronic kidney disease

Serum creatinine concentration, the classical biomarker of chronic kidney disease (CKD) in cats, has important limitations that decrease its value as a biomarker of early CKD. Recently, serum symmetric dimethylarginine concentration was introduced as a novel glomerular filtration rate biomarker for the early detection of CKD in cats. However, data on its specificity are still limited. The limitations of conventional biomarkers and the desire for early therapeutic intervention in cats with CKD to improve outcomes have prompted the discovery and validation of novel renal biomarkers to detect glomerular or tubular dysfunction. Changes in the serum or urinary concentrations of these biomarkers may indicate early kidney damage or predict the progression of kidney before changes in conventional biomarkers are detectable. This review summarizes current knowledge on renal biomarkers in CKD in cats, a field that has progressed substantially over the last 5 years.

First genome-wide association study investigating blood pressure and renal traits in domestic cats

Hypertension (HTN) and chronic kidney disease (CKD) are common in ageing cats. In humans, blood pressure (BP) and renal function are complex heritable traits. We performed the first feline genome-wide association study (GWAS) of quantitative traits systolic BP and creatinine and binary outcomes HTN and CKD, testing 1022 domestic cats with a discovery, replication and meta-analysis design. No variants reached experimental significance level in the discovery stage for any phenotype. Follow up of the top 9 variants for creatinine and 5 for systolic BP, one SNP reached experimental-wide significance for association with creatinine in the combined meta-analysis (chrD1.10258177; P = 1.34 × 10^–6). Exploratory genetic risk score (GRS) analyses were performed. Within the discovery sample, GRS of top SNPs from the BP and creatinine GWAS show strong association with HTN and CKD but did not validate in independent replication samples. A GRS including SNPs corresponding to human CKD genes was not significant in an independent subset of cats. Gene-set enrichment and pathway-based analysis (GSEA) was performed for both quantitative phenotypes, with 30 enriched pathways with creatinine. Our results support the utility of GWASs and GSEA for genetic discovery of complex traits in cats, with the caveat of our findings requiring validation.

Risk factors and implications associated with renal mineralization in chronic kidney disease in cats

Background

Nephrocalcinosis is a pathological feature of chronic kidney disease (CKD). Its pathophysiological implications for cats with CKD are unexplored.

Objectives

Identify nephrocalcinosis risk factors and evaluate its influence on CKD progression and all‐cause mortality.

Animals

Fifty‐one euthyroid client‐owned cats with International Renal Interest Society (IRIS) stages 2‐3 azotemic CKD.

Methods

Retrospective cohort study. Histopathological kidney sections were assessed for nephrocalcinosis (von Kossa stain). Nephrocalcinosis severity was determined by image analysis (ImageJ). Ordinal logistic regressions were performed to identify nephrocalcinosis risk factors. The influence of nephrocalcinosis on CKD progression and mortality risk were assessed using linear mixed model and Cox regression, respectively. Cats were categorized by their owner‐reported time‐averaged phosphate‐restricted diet (PRD) intake, where PRD comprised ≥50%, 10‐50%, or none of food intake.

Results

Nephrocalcinosis was rated as mild‐to‐severe in 78.4% and absent‐to‐minimal in 21.6% of cases. Higher baseline plasma total calcium concentration (tCa; odds ratio [OR] = 3.07 per 1 mg/dL; P = .02) and eating a PRD (10%‐50%: OR = 8.35; P = .01; ≥50%: OR = 5.47; P = .01) were independent nephrocalcinosis risk factors. Cats with absent‐to‐minimal nephrocalcinosis had increasing plasma creatinine (0.250 ± 0.074 mg/dL/month; P = .002), urea (5.06 ± 1.82 mg/dL/month; P = .01), and phosphate (0.233 ± 0.115 mg/dL/month; P = .05) concentrations over a 1‐year period, and had shorter median survival times than cats with mild‐to‐severe nephrocalcinosis.

Conclusion and Clinical Importance

Higher plasma tCa at CKD diagnosis and PRD intake are independently associated with nephrocalcinosis. However, nephrocalcinosis is not associated with rapid CKD progression in cats.

Is proteinuria a rare condition in apparently healthy and sick cats? A feline practice experience (2007-2018)

Background:

Proteinuria is assumed to be less frequent in cats than in dogs and is mainly associated with chronic kidney disease (CKD).

Aim:

The current study aimed to evaluate and compare urine protein-to-creatinine (UPC) values retrospectively in cats visited for comprehensive annual health check or for presenting systemic clinical signs related to CKD.

Methods:

UPC ratio was retrospectively evaluated in 112 owned cats, out of which 51 (45.5%) were apparently healthy cats according to their owners who visited for comprehensive annual health checks and 61 (54.5%) sick cats, presenting systemic clinical signs suggesting CKD, such as weight loss or polyuria/polydipsia, among others.

Results:

Based on UPC, the present study found that 54.5% of all cats included were borderline proteinuric or proteinuric, having increased UPC (UPC ≥ 0.2), with 35.7% included in the sick group and 18.7% in the health-check group. Increased UPC was also statistically associated with azotemia and isosthenuria (urinary-specific gravity between 1,008 and 1,035) in both sick and health-check groups of cats.

Conclusion:

Independent of the reason for their medical visit, it could be concluded that borderline proteinuria and proteinuria were statistically mainly related to CKD in cats. Furthermore, the measurement of UPC could be very useful in the detection and management of CKD in apparently healthy cats during a medical visit for annual health check irrespective of the age.

Feline comorbidities: The intermingled relationship between chronic kidney disease and hypertension

PRACTICAL RELEVANCE

Chronic kidney disease (CKD) is a highly prevalent disorder of senior cats. CKD is frequently diagnosed in association with hypertension, and the two conditions have an intermingled cause-and-effect relationship. Hypertensive target organ damage (TOD) to the eye, brain, heart and kidney significantly impacts the welfare of cats suffering from this comorbidity. Hypertension also drives proteinuria, which is an independent risk factor for progression and mortality in cats with CKD. Blood pressure monitoring and institution of effective antihypertensive treatment, where indicated, is therefore crucial in effective management of the feline CKD patient. Current guidelines recommend a target systolic blood pressure of <160 mmHg to minimise risk of TOD. Both amlodipine besylate and telmisartan are effective antihypertensive agents for use in these patients.

CLINICAL CHALLENGES

Clinical signs of hypertension may not be apparent to owners of affected cats until severe hypertensive TOD is present. Despite this, blood pressure monitoring in cats with CKD is still infrequently performed, and hypertension likely remains underdiagnosed in this population.

EVIDENCE BASE

This review is based upon evaluation of the currently available published literature, including relevant consensus statements. There is a large body of evidence supporting the association between hypertension and CKD in cats. However, significant aspects, such as the mechanisms behind this association, and effect of hypertension and antihypertensive treatment on mortality and progression of CKD, remain unclear. Further research is therefore required in order to improve understanding of these conditions.

Hyperammonemia in azotemic cats

OBJECTIVES

Hyperammonemia occurs in cats with hepatobiliary and nutritional (cobalamin and arginine deficiency) disorders, and has also been documented in four cats with renal azotemia. We hypothesized that in cats with renal azotemia, fasting hyperammonemia would correlate with indices of worsening kidney function, and would be independent of cobalamin, potassium, systemic inflammation or urinary tract infection (UTI) with urease-producing bacteria.

METHODS

A fasted blood sample was prospectively collected for ammonia and cobalamin analysis from 18 client-owned cats with renal azotemia (creatinine [Cr] ⩾1.6 mg/dl, urine specific gravity <1.030 or documentation of historical chronic kidney disease [CKD]). Correlations between blood ammonia and selected biochemical parameters were analyzed using Pearson's correlation coefficient.

RESULTS

Seven castrated males and 11 spayed females with a median age of 12 years (range 4-19 years) were enrolled. Ten of 18 (56%) cats presented for acute kidney injury (AKI) or acute on chronic kidney disease (AoCKD), and 8/18 (44%) presented for progressive CKD. The median Cr was 5.9 mg/dl (range 1.9-24.7 mg/dl). Hyperammonemia was documented in 4/18 (22%) cats, with a median of 95 µmol/dl (range 85-98 µmol/dl), and all four of these cats were classified as AKI/AoCKD. Blood ammonia concentrations had a significant moderate positive correlation between blood urea nitrogen (BUN) (r = 0.645, P = 0.003), Cr (r = 0.578, P = 0.012) and serum phosphorus (r = 0.714, P = 0.0009) but not with cobalamin, potassium or white blood cell count. No cats had UTIs with urease-producing bacteria.

CONCLUSIONS AND RELEVANCE

A correlation exists between blood ammonia and BUN, Cr and phosphorus in cats with renal azotemia. Future studies are warranted in a larger population of cats to determine the true prevalence, etiology and potential therapeutic effect of medical management of hyperammonemia on long-term prognosis in cats with kidney disease.

The impact of periodontal disease and dental cleaning procedures on serum and urine kidney biomarkers in dogs and cats

The objective of this study was to evaluate the benefits and inherent risks of dental cleaning procedures, based on serum and urine biomarkers for kidney function and tissue damage, in dogs and cats. Thirty-one asymptomatic, mostly older dogs (14 neutered male and 17 ovariohysterectomized female dogs of various breeds between 3 and 14 years old) and cats (19 neutered male and 12 ovariohysterectomized female domestic short hair cats between 2 and 16 years old) diagnosed with periodontal disease on physical exam, and recommended by their veterinarian to have dental cleaning under general anesthesia were evaluated in a prospective study. Serum and urine samples were collected from dogs and cats 1 week before, 6 hours after, and again 1 week after the dental cleaning procedure. Samples were analyzed for biomarkers of kidney function [serum creatinine (Cr), symmetric dimethylarginine (SDMA), and blood urea nitrogen (BUN), and urine for specific gravity (USG) and protein:creatinine (UPC) ratio]. A panel of biomarkers for renal tissue damage was also assessed [serum β-aminoisobutyric acid (BAIB), and urine cystatin B and clusterin]. Samples collected one week before dental cleaning procedures showed that increased age and severity of dental disease were linked to abnormal kidney function biomarker values (age: elevated SDMA and Cr concentrations and isosthenuric USG values; disease severity: elevated UPC ratios) as well as elevated urine cystatin B and clusterin concentrations. Directly after the dental cleaning procedure, an increased number of cats with elevated SDMA concentrations was observed (specifically in cats with longer duration of dental procedures). Extended duration of dental procedures (≥60 min) was linked to increased urine cystatin B and clusterin concentrations, whereas shorter duration procedures was linked to decreased urine cystatin B and clusterin. Higher SDMA concentrations persisted in cats one week after the dental cleaning procedures and were linked to elevated UPC ratios one week before cleaning procedures. In conclusion, the results of this study indicate a link between severity of dental disease, renal tissue injury, and impaired renal function. Longer duration dental procedures in cats may carry inherent risks of kidney injury and impaired renal function.

Influence of preanalytical factors on feline proteinuria

BACKGROUND

To date, little information is available about the effect of preanalytical factors on the urinary protein-to-creatinine (UPC) ratio in cats.

OBJECTIVES

We aimed to evaluate the effect of a commercially available cat litter, creatinine measurements at three different dilutions of urine, and different storage conditions on the UPC ratio in cats.

METHODS

Feline urine specimens were prospectively collected. Twenty-two whole-urine specimens were placed uncovered and in contact with cat litter for 1 hour; 25 urine supernatants were diluted 1:10, 1:20, and 1:100 for creatinine measurements. The correlation, difference, agreement, and concordance in classifying specimens according to International Renal Interest Society staging were determined. Storage effects on UPC ratios were assessed in specimens stored for 6 hours at +20℃ (n = 20), 1 week at +4℃ (n = 20), and 3 months at -20℃ (n = 25). Specimens were also subjected to four freeze-thaw cycles (n = 20). Results were compared, and clinical significance was assessed by comparing each UPC ratio to the inter-assay range of the baseline value.

RESULTS

Exposure to cat litter did not affect UPC ratios. A positive proportional bias was found in the 1:100 dilution compared with the 1:20 dilution; however, concordance was high for all comparisons. At +20, +4℃, and after four repeated freeze-thaw cycles, UPC ratios were stable. Compared with baseline values, UPC ratios decreased (P < .01) after 8 and 12 weeks at -20℃. However, all UPC ratios were within the inter-assay variability of the baseline value.

CONCLUSIONS

Exposure to cat litter did not affect UPC ratios, but further studies are necessary to evaluate other potential variables. The effects of the dilutions and storage conditions were clinically acceptable, although the 1:20 and 1:100 dilutions were not perfectly comparable.

Hypoxia and chronic kidney disease: Possible mechanisms, therapeutic targets, and relevance to cats

There is mounting evidence that kidney ischaemia/hypoxia plays an important role in feline chronic kidney disease (CKD) development and progression, as well as in human disease and laboratory animal models. Ischaemic acute kidney injury is widely accepted as a cause of CKD in people and data from laboratory species has identified some of the pathways underlying this continuum. Experimental kidney ischaemia in cats results in morphological changes, namely chronic tubulointerstitial inflammation, tubulointerstitial fibrosis, and tubular atrophy, akin to those observed in naturally-occurring CKD. Multiple situations are envisaged that could result in acute or chronic episodes of kidney hypoxia in cats, while risk factors identified in epidemiological studies provide further support that kidney hypoxia contributes to spontaneously occurring feline CKD. This review evaluates the evidence for the role of kidney ischaemia/hypoxia in feline CKD and the proposed mechanisms and consequences of kidney hypoxia. As no effective treatments exist that substantially slow or prevent feline CKD progression, there is a need for novel therapeutic strategies. Targeting kidney hypoxia is one such promising approach, with therapies including those that attenuate the hypoxia-inducible factor (HIF) pathway already being utilised in human CKD.

2021 AAFP Feline Senior Care Guidelines

The '2021 AAFP Feline Senior Care Guidelines' are authored by a Task Force of experts in feline clinical medicine and serve as an update and extension of those published in 2009. They emphasize the individual patient evaluation and the process of aging, with references to other feline practice guidelines for a more complete discussion of specific diseases. Focusing on each cat encourages and empowers the owner to become a part of the cat's care every step of the way. A comprehensive discussion during the physical examination and history taking allows for tailoring the approach to both the cat and the family involved in the care. Videos and analysis of serial historical measurements are brought into the assessment of each patient. These Guidelines introduce the emerging concept of frailty, with a description and methods of its incorporation into the senior cat assessment. Minimum database diagnostics are discussed, along with recommendations for additional investigative considerations. For example, blood pressure assessment is included as a minimum diagnostic procedure in both apparently healthy and ill cats. Cats age at a much faster rate than humans, so practical timelines for testing frequency are included and suggest an increased frequency of diagnostics with advancing age. The importance of nutrition, as well as senior cat nutritional needs and deficiencies, is considered. Pain is highlighted as its own syndrome, with an emphasis on consideration in every senior cat. The Task Force discusses anesthesia, along with strategies to allow aging cats to be safely anesthetized well into their senior years. The medical concept of quality of life is addressed with the latest information available in veterinary medicine. This includes end of life considerations like palliative and hospice care, as well as recommendations on the establishment of 'budgets of care', which greatly influence what can be done for the individual cat. Acknowledgement is given that each cat owner will be different in this regard; and establishing what is reasonable and practical for the individual owner is important. A discussion on euthanasia offers some recommendations to help the owner make a decision that reflects the best interests of the individual cat.

Chemokine Therapy in Cats With Experimental Renal Fibrosis and in a Kidney Disease Pilot Study

Background: Chronic tubulointerstitial fibrosis is a common final pathway leading to end stage kidney disease in cats and has no effective treatment. The use of cell-based molecules to treat kidney fibrosis may be a promising approach. The objectives were to test the effects of intra-renal chemokine CXCL12 injection in a pre-clinical cat model of unilateral ischemia/reperfusion (I/R)-induced kidney fibrosis and then, within a clinical pilot study, test the safety/feasibility of CXCL12 injection in cats that might have early chronic kidney disease (CKD). Methods: Pre-clinical: Thirty cats received intra-renal injection of 100, 200, or 400 ng of recombinant human CXCL12, or sterile saline, into the I/R kidney 70 days post-injury, or were non-injured, non-injected controls (n = 6/group). Kidney collagen content was quantified 4 months post-treatment using Masson's Trichrome and Picrosirius Red (PSR) stained tissues. In a separate study (n = 2) exploring short-term effects of CXCL12, 200 ng CXCL12 was injected into I/R kidneys and then harvested either 30 min (n = 1) or 1 month (n = 1) post-injection. Kidney concentrations of CXCL12, matrix metalloproteinase 1 (MMP-1), and lysyl oxidase-like enzyme 2 (LOXL-2) were quantified via ELISA. Clinical Pilot: 14 client-owned cats with potential early kidney disease received a single-treatment, bilateral intra-renal injection of 200 ng CXCL12 (n = 7), or received no injection (n = 7). Blood/urine samples were collected monthly for 9 months to assess renal function and CKD staging. Results: Pre-clinical: I/R increased the affected kidney collagen content, which both mid and high doses of CXCL12 restored to normal (ps < 0.05 vs. untreated). I/R increased collagen fiber width, which both mid and high doses of CXCL12 restored to normal (p < 0.001 vs. untreated). Early changes in kidney MMP-1, associated with collagen breakdown, and subsequent decreases in LOXL-2, associated with collagen cross-linking, in response to CXCL12 treatment may contribute to these findings. Clinical Pilot: Bilateral intra-renal injection of CXCL12 using ultrasound guidance in cats with CKD was feasible and safe in a general practice clinical setting with no obvious side effects noted during the 9-month follow-up period. Conclusions: Intra-renal injection of CXCL12 may prove to be an effective treatment for kidney fibrosis in cats with CKD. Additional mechanistic and clinical evaluations are needed.

Distinctive egg-laying patterns in terminal versus non-terminal periods in three fruit fly species

The specific objective of this study was to use a logistic regression model for determining the degree to which egg laying patterns of individual females at the end of life (i.e., terminal segments) in each of three different fruit fly species could be distinguished from the egg-laying patterns over a similar period in midlife (i.e., non-terminal segments). Extracting data from large-scale databases for 11-day terminal and 11-day non-terminal segments in the vinegar fly (Drosophila melanogaster), the Mexican fruit fly (Anastrepha ludens) and the Mediterranean fruit fly (Ceratitis capitata) and organizing the model's results in a 2 × 2 contingency table, we found that: (1) daily egg-laying patterns in fruit flies can be used to distinguish terminal from non-terminal periods; (2) the overall performance metrics such as precision, accuracy, false positives and true negatives depended heavily on species; (3) differentiating between terminal and non-terminal segments is more difficult when flies die at younger ages; and (4) among the three species the best performing metrics including accuracy and precision were those produced using data on D. melanogaster. We conclude that, although the reliability of the prediction of whether a segment occurred at the end of life is relatively high for most species, it does not follow precisely predicting remaining life will also be highly reliable since classifying an end of life period is a fundamentally different challenge than is predicting an exact day of death.

Effects of low-dose meloxicam in cats with chronic kidney disease

OBJECTIVES

Meloxicam therapy may benefit cats with degenerative joint disease, and retrospective studies suggest it could slow kidney disease progression and increase survival. This study aimed to prospectively evaluate the renal effects of low-dose meloxicam treatment (0.02 mg/kg/day) over 6 months in cats with chronic kidney disease (CKD).

METHODS

Twenty-one cats with stable International Renal Interest Society stage 2 or 3 CKD were recruited and randomized to placebo or meloxicam groups. Cats were evaluated at baseline and at 1, 3 and 6 months, including blood pressure, chemistry, symmetric dimethylarginine (SDMA), glomerular filtration rate (GFR), urinalysis, urine protein:creatinine ratio (UPC), urine transforming growth factor-beta (β):creatinine ratio, urine clusterin, urine cystatin B and serum inosine.

RESULTS

No statistical difference was observed in systolic blood pressure, blood urea nitrogen, creatinine, SDMA, GFR, urine transforming growth factor-β:creatinine ratio, urine clusterin, urine cystatin B or serum inosine in cats receiving meloxicam vs placebo. Mean UPC was greater in the meloxicam group (0.33) than the placebo group (0.1) at 6 months (P = 0.006). Four cats had meloxicam discontinued owing to potential (mainly gastrointestinal) adverse effects.

CONCLUSIONS AND RELEVANCE

No decline in renal excretory function was observed when meloxicam was administered to cats with CKD. However, gastrointestinal adverse effects were observed, and cats that received meloxicam had greater proteinuria at 6 months than cats that received placebo. As proteinuria is associated with negative outcomes (progression of azotemia and hypertension) in cats with CKD, this finding suggests that meloxicam should be used with caution in cats with CKD and UPC monitored. Until further research is available, clinicians should weigh the risk of potential increased proteinuria against quality of life benefits when considering meloxicam for analgesia in cats with renal disease.

The effect of attenuating dietary phosphate restriction on blood ionized calcium concentrations in cats with chronic kidney disease and ionized hypercalcemia

Background

Hypercalcemia is commonly observed in cats with azotemic chronic kidney disease (CKD). Dietary phosphate restriction is considered standard of care but may contribute to the development of hypercalcemia. The optimal dietary management strategy for these cats is unclear.

Objectives

To describe the effect of feeding a moderately phosphate‐restricted diet (MP; 1.5 g/Mcal phosphorus; Ca : P ratio, 1.3) to cats with concurrent azotemic CKD and ionized hypercalcemia.

Animals

Client‐owned cats with ionized hypercalcemia (ionized calcium [iCa] concentration >1.4 mmol/L) at diagnosis of CKD (n = 11; baseline hypercalcemics) or after CKD diagnosis while eating a phosphate‐restricted clinical renal diet (0.8 g/Mcal phosphorus; Ca : P ratio, 1.9; n = 10; RD hypercalcemics).

Methods

Changes in variables over time, after starting MP at visit 1, were assessed using linear mixed model analysis within each group of cats. Data are reporte as median [25th, 75th percentiles].

Results

At visit 1, iCa was 1.47 [1.42, 1.55] mmol/L for baseline hypercalcemics and 1.53 [1.5, 1.67] mmol/L for RD hypercalcemics. Blood iCa decreased (P < .001) when RD hypercalcemics were fed MP, with iCa <1.4 mmol/L in 8/10 cats after 2.2 [1.8, 3.7] months. Plasma phosphate concentrations did not change. In contrast, the baseline hypercalcemic group overall showed no change in iCa but a decrease in plasma phosphate concentration during 8.8 [5.5, 10.6] months on the MP diet, although 4/11 individual cats achieved iCa <1.4 mmol/L by 3.4 [1.0, 6.2] months.

Conclusions and Clinical Importance

Attenuation of dietary phosphate restriction could result in normalization of iCa in cats that develop hypercalcemia while eating a clinical renal diet.

Risk factors associated with disturbances of calcium homeostasis after initiation of a phosphate-restricted diet in cats with chronic kidney disease

BACKGROUND

Dietary phosphate restriction improves survival in cats with chronic kidney disease (CKD). However, feeding a phosphate-restricted diet may disrupt calcium homeostasis leading to hypercalcemia in some cats.

OBJECTIVES

To identify risk factors associated with increasing plasma total calcium (tCa) concentration after transition to a phosphate-restricted diet and to explore its role in CKD-mineral and bone disorder (CKD-MBD) in cats.

ANIMALS

Seventy-one geriatric (≥9 years) euthyroid client-owned cats with International Renal Interest Society (IRIS) stage 2 to 3 azotemic CKD.

METHODS

Retrospective cross-sectional cohort study. Changes in plasma tCa concentration in the first 200 days of diet transition were assessed using linear regression. Binary logistic regressions were performed to identify risk factors for increasing calcium concentration. Changes in clinicopathological variables associated with CKD-MBD over time were explored using linear mixed model and generalized linear mixed model analyses.

RESULTS

Lower baseline plasma potassium (odds ratio [OR] = 1.19 per 0.1 mmol/L decrease; P = .003) and phosphate (OR = 1.15 per 0.1 mmol/L decrease; P = .01) concentrations remained independent risk factors for increasing plasma tCa concentration. Plasma creatinine (β = .069 ± .029 mg/dL; P = .02), symmetric dimethylarginine (β = .64 ± .29 μg/dL; P = .03), phosphate (β = .129 ± .062 mg/dL; P = .04), and ln[FGF23] (β = .103 ± .035 pg/mL; P = .004) concentrations had significantly increased rates of change in cats with increasing plasma tCa concentration over time.

CONCLUSION AND CLINICAL IMPORTANCE

Lower plasma potassium or phosphate concentrations or both at the time of transition of cats with CKD to a phosphate-restricted diet are independently associated with increased risk of an increase in plasma tCa concentration. Increasing plasma tCa concentration is associated with progression of CKD.

Investigation of the transforming growth factor-beta 1 signalling pathway as a possible link between hyperphosphataemia and renal fibrosis in feline chronic kidney disease

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Chronic kidney disease (CKD) is associated with development of hyperphosphataemia.

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Severity of renal fibrosis has been correlated with degree of hyperphosphataemia.

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Transforming growth factor-β1 (TGF-β1) is a major pro-fibrotic mediator in CKD.

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A phosphate restricted diet did not affect urinary active TGF-β1 excretion in cats.

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Increased extracellular phosphate had no pro-fibrotic effect on feline renal cells.

Chronic kidney disease (CKD) is common in geriatric cats, and is characterised in the majority of cases by tubulointerstitial inflammation and fibrosis. Hyperphosphataemia is a frequent complication of CKD and is independently associated with severity of renal fibrosis and disease progression. Transforming growth factor-beta 1 (TGF-β1) signalling is thought to be a convergent pathway which mediates the progression of renal fibrosis in CKD. The aims of this study were to explore the interaction between increased extracellular phosphate and the TGF-β1 signalling pathway by investigating: (a) the effect of a commercially available, phosphate-restricted, diet on urinary TGF-β1 excretion in cats with CKD; and (b) the role of increased extracellular phosphate in regulating proliferation, apoptosis, and expression of genes related to TGF-β1 signalling and extracellular matrix (ECM) production in feline proximal tubular epithelial cells (FPTEC) and cortical fibroblasts from cats with azotaemic CKD (CKD-FCF).

The dietary intervention study revealed no effect of dietary phosphate restriction on urinary active TGF-β1 excretion after 4–8 weeks (P = 0.98), despite significantly decreasing serum phosphate (P < 0.001). There was no effect of increased growth media phosphate concentration (from 0.95 mM to 2 mM and 3.5 mM) on proliferation (P = 0.99) and apoptotic activity in FPTEC (P = 0.22), or expression of genes related to ECM production and the TGF-β1 signalling pathway in FPTEC and CKD-FCF (P > 0.05). These findings suggest the beneficial effects of dietary phosphate restriction on progression of feline CKD may not occur through modulation of renal TGF-β1 production, and do not support a direct pro-fibrotic effect of increased extracellular phosphate on feline renal cells.

The new age of renal biomarkers: does SDMA solve all of our problems?

Within clinical small animal practice, diagnosis of both chronic kidney disease and acute kidney injury is common. To assess renal function, measurement of glomerular filtration rate is considered the gold standard. Currently, routine tests of kidney function include surrogate markers of glomerular filtration rate such as serum creatinine, and urea, each with their own limitations, whilst urine protein to creatinine ratio gives an indication of glomerular and tubular handling of protein, and urine specific gravity information about urine concentrating ability by the kidney. These parameters are used together with historical and physical examination data to give a diagnosis of kidney disease following which creatinine, proteinuria and blood pressure are used to stage chronic kidney disease and, together with urine output, grade acute kidney injury according to the International Renal Interest Society. However, there has been much concern that creatinine is insensitive when used to indicate early decline in renal function and this has highlighted the need for additional methods of diagnosing and monitoring these patients, with the potential to allow earlier therapeutic intervention. Symmetric dimethylarginine is a novel biomarker, which has been shown to perform as a surrogate marker of glomerular filtration rate in small animals. This article will review current research on symmetric dimethylarginine and the ways in which it may be utilised in small animal practice; current research supports the use of symmetric dimethylarginine as a screening test for detection of early chronic kidney disease according to International Renal Interest Society guidelines, but further research is required in to the usefulness of symmetric dimethylarginine as a tool for monitoring disease and the effect of non-renal influences.

A review of phosphorus homeostasis and the impact of different types and amounts of dietary phosphate on metabolism and renal health in cats

Elevated concentrations of serum phosphate are linked with progression and increased case fatality rate in animals and humans with chronic kidney disease. Elevated concentrations of serum phosphate can be a risk factor for development of renal and cardiovascular diseases or osteoporosis in previously healthy people. In rodents, an excess intake of dietary phosphorus combined with an inverse dietary calcium : phosphorus ratio (<1 : 1) contributes to renal calcification. Renal injury also has occured in cats fed experimental diets supplemented with highly soluble phosphate salts, especially in diets with inverse calcium : phosphorus ratios. However, not all phosphorus sources contribute similarly to this effect. This review, which focuses on cats, summarizes the published evidence regarding phosphorus metabolism and homeostasis, including the relative impact of different dietary phosphorus sources, and their impact on the kidneys. No data currently shows that commercial cat foods induce renal injury. However, some diets contain high amounts of phosphorus relative to recommendations and some have inverse Ca : P ratios and so could increase the risk for development of kidney disease. While limiting the use of highly soluble phosphates appears to be important, there are insufficient data to support a specific upper limit for phosphate intake. This review also proposes areas where additional research is needed in order to strengthen conclusions and recommendations regarding dietary phosphorus for cats.

Acute on chronic kidney disease in dogs: Etiology, clinical and clinicopathologic findings, prognostic markers, and survival

BACKGROUND

Chronic kidney disease (CKD) and acute exacerbation of CKD (ACKD) are common in dogs.

OBJECTIVE

To characterize the etiology, clinical and laboratory findings, and short- and long-term prognosis of dogs with ACKD.

ANIMALS

One hundred dogs with ACKD.

METHODS

Medical records of dogs diagnosed with ACKD admitted to a veterinary teaching hospital were retrospectively reviewed.

RESULTS

The most common clinical signs included anorexia (84%), lethargy (77%), vomiting (55%) and diarrhea (37%). Presumptive etiology included inflammatory causes (30%), pyelonephritis (15%), ischemic causes (7%), other (3%), or unknown (45%). Median hospitalization time was 5 days (range, 2-29 days) and was significantly longer in survivors (6 days; range, 2-29 days) compared with nonsurvivors (4 days; range, 2-20 days; P < .001). Mortality rate was 35%. International Renal Interest Society (IRIS) acute kidney injury (AKI) grade at presentation was associated (P = .009) with short-term survival, but presumptive etiology was not (P = .46). On multivariable analysis; respiratory rate (P = .01), creatine kinase (CK) activity (P = .005) and serum creatinine concentration (SCR; P = .04) at presentation were associated with short-term outcome. Median survival time of dogs discharged was 105 days (95% confidence interval [CI], 25-184), with 35 and 8 dogs surviving up to 6 and 12 months, respectively. Presumptive etiology (P = .16) and SCR (P = .59) at discharge were not predictors of long-term survival.

CONCLUSION AND CLINICAL IMPORTANCE

Short-term outcome of dogs with ACKD is comparable to those with AKI but long-term prognosis is guarded. The IRIS AKI grade at presentation is a prognostic indicator of short-term outcome.

The association of bacteriuria with survival and disease progression in cats with azotemic chronic kidney disease

BACKGROUND

Cats with chronic kidney disease (CKD) have an increased prevalence of positive urine cultures (PUC). Limited information is available regarding the prognosis of cats with CKD and concurrent PUC.

OBJECTIVE

To determine the association of PUC with survival time and disease progression in cats with CKD.

ANIMALS

Medical records of 509 cats diagnosed with azotemic CKD between 1997 and 2018.

METHODS

Cats were classified as having "no-PUC" or "PUC." The PUC cats were further classified as having 1 or multiple PUC, and also were classified based on the presence or absence of clinical signs of urinary tract infection (UTI). Progression of CKD was defined as a plasma creatinine concentration increase of ≥25% within 365 days of CKD diagnosis; PUC also must have occurred within this time frame. Survival time and frequency of CKD progression were compared between groups.

RESULTS

No significant difference in survival time was found between cats with no-PUC and cats with any number of PUC (P = .91), or between cats with no-PUC, 1 PUC or multiple PUC (P = .37). Also, no significant difference was found in the frequency of CKD progression between PUC and no-PUC cats (P = .5), or among no-PUC, 1 PUC and multiple PUC cats (P = .22). When assessing cats with clinical signs of lower UTI, no significant difference was found in the frequency of CKD progression between cats with true UTI, subclinical bacteriuria or no-PUC (P = .8).

CONCLUSIONS AND CLINICAL IMPORTANCE

When treated with antibiotics, PUC in cats with CKD do not affect disease progression or survival time.

Clinicopathologic characteristics, pathology, and prognosis of 77 dogs with focal segmental glomerulosclerosis

BACKGROUND

Focal segmental glomerulosclerosis (FSGS) is a common cause of nonimmune complex glomerulopathy and the prognosis and clinicopathologic findings associated with this condition have not been described in dogs.

OBJECTIVE

To characterize the presentation and identify clinical factors associated with the survival of dogs with FSGS.

ANIMALS

Seventy-seven dogs diagnosed with FSGS based on evaluation of renal biopsy samples submitted to the International Veterinary Renal Pathology Service.

METHODS

Retrospective review of medical records of dogs biopsied for evaluation of proteinuria between January 2015 and May 2017.

RESULTS

The incidence of FSGS among all dogs biopsied for proteinuria was 26%. Significantly more females (48; 62.3%) than males (29; 37.7%) were affected (P = .04). At the time of biopsy, median serum creatinine concentration (SCr) was 1.2 mg/dL (range, 0.3-8.7), median serum albumin concentration (Alb) was 2.8 g/dL (range, 1.1-4.6), median systolic blood pressure was 153.5 mm Hg (range, 95-260), and median urine protein : creatinine ratio was 5.9 (range, 1.4-22). Median survival time after biopsy was 258 days (range, 26-1003) for dogs that died from all causes (n = 32). Factors that were associated with a shorter survival time included SCr ≥ 2.1 mg/dL (P < .01) and Alb < 2 g/dL (P < .01).

CONCLUSIONS AND CLINICAL IMPORTANCE

Most dogs with FSGS were female, and although commonly hypertensive, azotemia, severe hypoalbuminemia and ascites or edema were observed infrequently. Variables significantly associated with survival time were SCr and Alb.

Diagnostic utility of different models used to assess the acid-base balance in cats with chronic kidney disease

Metabolic acidosis is diagnosed based on the concentration of bicarbonate ions and partial pressure of carbon dioxide in arterial blood, although acid-base balance (ABB) disorders may also be diagnosed based on the serum ion concentrations in order to determine the values of strong ion difference (SID), anion gap (AG), corrected anion gap (AGcorr) and chloride/sodium ratio (Cl-/Na+). The aim of this study was to assess and compare the classic model, the value of the AG, AGcorr, and Cl-/Na+ in the diagnosis of ABB disorders in cats with chronic kidney disease (CKD). The study group consisted of 80 cats with CKD, divided into four groups based on the guidelines of the International Renal Interest Society (IRIS). The control group (C) included 20 healthy cats. Metabolic acidosis - diagnosed based on the classic model (Hendersson-Hasselbalch equation) - was found in IRIS group IV. AG, AGcorr, SID calculated for IRIS groups II, III and IV were lower than in group C, while the value of AGdiff and Cl-/Na+ in those groups was higher than in group C. We can conclude that ABB analysis using the classic model enabled the detection of ABB disorders in cats in stage IV CKD. However, the analysis of the AG, AGcorr and Cl-/Na+ values enabled the diagnosis of acid-base balance disorders in cats with IRIS stage II, III and IV CKD.

The utility of combined urine dipstick analysis and specific gravity measurement to determine feline proteinuria

OBJECTIVES

To assess the utility of urine dipstick strips for detection of feline proteinuria when used in combination with urine-specific gravity, compared with urine protein-to-creatinine ratio as the gold standard.

MATERIALS AND METHODS

Retrospective analysis of clinical records of comprehensive urine examination obtained from cats presented to a referral hospital. Diagnostic agreement and test accuracy were calculated for the dipstick test alone and in combination with the urine-specific gravity, using different cut-off values for proteinuria. Receiver-operating characteristic curves were also calculated.

RESULTS

A total of 121 urine samples were included. The diagnostic agreement between dipstick and urine protein-creatinine ratio was poor. A dipstick result of equal or greater than "Trace" (0.1-0.3 g/L) had a sensitivity of 81% and a specificity of 31% to detect proteinuria. Grouping the samples by urine-specific gravity did not increase dipstick agreement with the urine protein-creatinine ratio and only resulted in a slight improvement in the accuracy of detecting proteinuria.

CLINICAL SIGNIFICANCE

The dipstick test was not accurate for detecting proteinuria when combined with urine-specific gravity in cats. Clinicians should not rely on this test and, regardless of the urine concentration, other appropriate quantitative methods such as urine protein-creatinine ratio should always be performed to detect proteinuria in cats.

Hypertension: Why Is It Critical?

Hypertension is a common problem, particularly in older cats. Hypertension secondary to a concurrent disease is the most common form of hypertension in cats, particularly in association with chronic kidney disease or hyperthyroidism. However, idiopathic hypertension may account for up to 24% of cases. Any form of persistent hypertension risks target organ damage (TOD), therefore measurement of blood pressure is vital in at-risk cats to identify occult hypertension before TOD occurs. This article addresses when and how to perform blood pressure measurement in cats, TOD that has been documented in this species, and our evidence basis for treating hypertension.

Retrospective study of the efficacy of oral potassium supplementation in cats with kidney disease

OBJECTIVES

The aim of this study was to assess the effect of three oral potassium supplements (potassium gluconate tablets [PGT], potassium gluconate granules [PGG] and potassium citrate granules [PCG]) on hypokalemia and serum bicarbonate in cats with chronic kidney disease (CKD).

METHODS

Medical records (2006-2016) were retrospectively searched for cats that had been prescribed an oral potassium supplement for management of their CKD-associated hypokalemia. For inclusion, laboratory work had to be available at the time of hypokalemia diagnosis, and at recheck within 1-6 weeks. Treatment response was defined in three ways: any increase in potassium, an increase in potassium to within the normal reference interval, and an increase to >4 mEq/l.

RESULTS

Thirty-seven cats met inclusion criteria (16 PGT, 11 PGG, 10 PCG). Dosing ranged from 0.21 to 1.6 mEq/kg/day for PGT, from 0.25 to 1.48 mEq/kg/day for PGG and from 0.04 to 1.34 mEq/kg/day for PCG. After supplementation, 36/37 cats had an increase in potassium, 34/37 increased to within the reference interval and 24/37 had an increase in potassium to >4 mEq/l. There was a statistically significant difference in serum potassium post-supplementation for all three treatments: PGT (P = 0.0001), PGG (P = 0.001) and PCG (P = 0.002). There was a positive correlation between PGT dose and change in potassium concentration (P = 0.04), but there was no significant correlation for PGG or PCG. In cats that had data available, serum bicarbonate increased >2 mEq/l in 1/6 PGT, 1/6 PGG and 3/4 PCG cats.

CONCLUSIONS AND RELEVANCE

All three potassium supplements were effective in treating hypokalemia secondary to CKD in the majority of cats despite variable dosing. Data were limited to assess the alkalinizing effect and prospective studies are needed.

Acute on chronic kidney disease in cats: Etiology, clinical and clinicopathologic findings, prognostic markers, and outcome

Background

Chronic kidney disease (CKD) and acute decompensation of CKD (ACKD) are common in cats.

Objectives

To characterize the etiology, clinical and clinicopathologic findings, and the short‐ and long‐term prognosis of feline ACKD.

Animals

One hundred cats with ACKD.

Methods

Retrospective study, search of medical records for cats with ACKD.

Results

Common clinical signs included anorexia (85%), lethargy (60%), weight loss (39%), and vomiting (27%). Suspected etiologies included ureteral obstruction (11%), renal ischemia (9%), pyelonephritis (8%), others (6%), or unknown (66%). Hospitalization duration was longer in survivors versus nonsurvivors (median = 7 days, range = 2‐26 versus median = 3 days, range = 2‐20, respectively, P < .001). The survival rate to discharge was 58%. Age, serum creatinine, urea, and phosphorous concentrations were higher and venous blood pH was lower in nonsurvivors. However, only serum phosphorus remained associated with the short‐term outcome in the multivariable model (P = .02; 95% confidence interval = 1.03‐1.39). Survivors had a median survival time of 66 days after discharge. Serum creatinine concentrations at presentation as well as at discharge were associated with long‐term survival (P < .002 for both).

Conclusions

The short‐term prognosis of ACKD is comparable to acute kidney injury, while the long‐term prognosis is guarded.

Complex Disease Management: Managing a Cat with Comorbidities

Many older cats often suffer concurrently from multiple conditions. By focusing on the common concerns, rather than conflicting requirements, a management program can be devised. Optimize hydration, nutrition, and ensure comfort though providing analgesia and a low-stress environment in which the patient's feline-specific nature is respected both in the clinic and at home. Additional requirements, such as hyperphosphatemia or hypokalemia, can be met using treatments outside of diet, if necessary.

Aldosterone and the mineralocorticoid receptor in renal injury: A potential therapeutic target in feline chronic kidney disease

There is a growing body of experimental and clinical evidence supporting mineralocorticoid receptor (MR) activation as a powerful mediator of renal damage in laboratory animals and humans. Multiple pathophysiological mechanisms are proposed, with the strongest evidence supporting aldosterone-induced vasculopathy, exacerbation of oxidative stress and inflammation, and increased growth factor signalling promoting fibroblast proliferation and deranged extracellular matrix homeostasis. Further involvement of the MR is supported by extensive animal model experiments where MR antagonists (such as spironolactone and eplerenone) abrogate renal injury, including ischaemia-induced damage. Additionally, clinical trials have shown MR antagonists to be beneficial in human chronic kidney disease (CKD) in terms of reducing proteinuria and cardiovascular events, though current studies have not evaluated primary end points which allow conclusions to made about whether MR antagonists reduce mortality or slow CKD progression. Although differences between human and feline CKD exist, feline CKD shares many characteristics with human disease including tubulointerstitial fibrosis. This review evaluates the evidence for the role of the MR in renal injury and summarizes the literature concerning aldosterone in feline CKD. MR antagonists may represent a promising therapeutic strategy in feline CKD.

Renal expression and urinary excretion of liver-type fatty acid-binding protein in cats with renal disease

Background

Liver‐type fatty acid‐binding protein (L‐FABP) is a biomarker for early detection of renal disease in humans. Liver‐type fatty acid‐binding protein is cytotoxic oxidation products secreted from proximal tubules under ischemia and oxidative stress.

Objective

To examine renal expression and quantify urinary excretion of L‐FABP in catswith renal disease.

Animals

One hundred and thirty‐four client‐owned cats including 34 cats with serum creatinine (sCre) values >1.6 mg/dL and 10 other cats that died in clinics.

Methods

Tissue expressions of L‐FABP were examined by reverse transcription polymerase chain reaction and Western blotting. Urinary L‐FABP (uL‐FABP) and serum L‐FABP (sL‐FABP) levels were determined by enzyme‐linked immunosorbent assay. Anti‐liver‐type fatty acid‐binding protein antibody immunostained renal sections.

Results

Feline kidneys express L‐FABP. Strong L‐FABP signals were observed in the lumens of proximal tubular cells in 5 cats with high uL‐FABP excretion, but not in 5 cats with low uL‐FABP excretion. In 9 normal cats, uL‐FABP index was <1.2 μg/g urinary creatinine (uCre). High uL‐FABP indexes (>10.0 μg/g uCre) were detected in 7 of 100 cats with low sCre (<1.6 mg/dL) and 18 of 44 cats with high sCre (>1.6 mg/dL). There was a weak correlation between L‐FABP index and sCre, serum symmetric dimethylarginine (SDMA), or blood urea nitrogen (BUN), and these correlation coefficients were increased by analyzing only data of cats with sCre >1.6 mg/dL. There was a weak correlation between u L‐FABP index and sL‐FABP in all tested cats, but not in cats with high sCre.

Conclusions and Clinical Importance

This study demonstrates correlations between L‐FABP and current renal biomarkers for chronic kidney disease in cats, such as sCre and SDMA. Liver‐type fatty acid‐binding protein may be a potential biomarker to predict early pathophysiological events in feline kidneys.

Electrophoretic patterns of proteinuria in feline spontaneous chronic kidney disease

OBJECTIVES

The purpose of this study was to describe the electrophoretic patterns of proteinuria in cats at risk of and cats with chronic kidney disease (CKD), and to investigate whether the presence of high-molecular-weight (HMW) and low-molecular-weight (LMW) proteins were associated with CKD, proteinuria and/or disease progression.

METHODS

Healthy cats at risk of developing renal disease (n = 17) and cats affected with CKD at different stages (n = 22) were prospectively enrolled and sampled over time. Seventy urine samples were included and assayed with a commercially available sodium dodecyl sulfate-agarose gel electrophoresis (SDS-AGE) method. Each sample (gel lane) was inspected to identify albumin, HMW and LMW proteins, and an electrophoretic pattern (albuminuria, glomerular, tubular, mixed or negative) was assigned accordingly. Fisher's exact test was used to assess the distribution of HMW and LMW proteins in cats grouped according to International Renal Interest Society stage and to the magnitude of proteinuria, and to assess if HMW and LMW proteins at the time of inclusion were associated with the development and progression of CKD.

RESULTS

In samples of cats at risk, the most common pattern was glomerular (84.6%); glomerular pattern was also common in cats with CKD (54.2%), although mixed proteinuria and tubular proteinuria were also present (29.5% and 11.4%, respectively). The presence of LMW proteins was associated with CKD (P <0.0001) and to a urine protein:creatinine ratio >0.2 (P = 0.025). Both HMW and LMW proteins were not associated with progression of CKD within 6 months (n = 14).

CONCLUSIONS AND RELEVANCE

Our results showed that HMW proteinuria is common in healthy cats at risk of developing CKD, although the pathological significance needs to be confirmed. The detection of LMW proteins in urine of cats suspected to be affected by CKD, especially in non-azotaemic, non-proteinuric or borderline proteinuric cats, suggests the presence of kidney damage.

Measurements of echocardiographic indices and biomarkers of kidney injury in dogs with chronic kidney disease

Pathophysiological cardiac and renal interactions are termed cardiovascular-renal disorder (CvRD). Cardiovascular disease/dysfunction secondary to kidney disease (CvRD_K), is a leading cause of death in human chronic kidney disease (CKD) patients. The presence and clinical impact of CvRD_K in dogs with CKD is unknown. We hypothesized that echocardiographic measurements, and cardiac and renal biomarkers, will be altered in dogs with CKD and associated with survival. Eleven dogs with CKD (n = 6 IRIS stage 2, n = 5 IRIS stage 3) and without primary cardiac disease, plus 12 healthy age-matched control dogs, were recruited to this prospective observational study. Dogs underwent standard echocardiography, glomerular filtration rate (GFR) estimation by iohexol clearance, and measurement of plasma cardiac troponin I and N-terminal pro-B-type natriuretic peptide (NT-proBNP), plasma and urinary cystatin B, and urinary clusterin and neutrophil gelatinase-associated lipocalin (NGAL). Values were compared between groups, and their association with all-cause mortality explored. Dogs with CKD had significantly lower GFR and higher NT-proBNP, urinary cystatin B, clusterin, and NGAL, compared to controls (P < 0.05). Echocardiographic measurements were similar between dogs with CKD and controls. Median follow-up time was 666 days, during which six dogs with CKD died. Risk of death was associated with increasing age, serum total protein, and normalized left ventricular posterior wall thickness (LVPWDN) and decreasing bodyweight and packed cell volume. Although baseline differences in echocardiographic measurements were not evident between dogs with moderate CKD and controls, the presence of CvRD_K was suggested by the association between LVPWDN and survival.

A specific immunoassay for detection of feline kidney injury molecule 1

OBJECTIVES

The aim of this study was to design and carry out a preliminary evaluation of a urine point-of-care test for kidney injury molecule 1 (KIM-1) in healthy and diseased cats.

METHODS

Part of the feline KIM-1 gene was amplified, ligated into a plasmid with a signal peptide and monomeric human IgGFc, and transfected into a mammalian cell line. Supernatant was purified and tested for the fusion protein by gel electrophoresis and Western blot. Mice were immunized three times with purified proteins, and hybridomas were generated from splenocytes. Antibodies were tested by ELISA for detection of recombinant KIM-1 and naturally occurring KIM-1 in disease-state urine. Next, a lateral flow assay (LFA) with capture and detection antibodies was constructed, and tested with 34 urine samples from healthy and diseased cats. Antibodies were also tested for reactivity with formalin-fixed paraffin-embedded kidney tissue.

RESULTS

Three antibodies were assessed. Antibodies detected between 0.4 and 60 ng/ml feline KIM-1 fusion protein in the LFA. Urine samples from healthy cats yielded faint bands in the LFA corresponding to optical density (OD) values of 4.8-8.8. Samples from cats with suspected or confirmed acute kidney injury (AKI) had OD values ranging from 1.6-20.5. Urine KIM-1 varied over multiple days in cats with sepsis or urethral obstruction despite normalizing serum creatinine concentration. In tissue sections, KIM-1 antibodies labeled tubular cells with morphological features of injury.

CONCLUSIONS AND RELEVANCE

A practical patient-side assay for detection of KIM-1 in feline urine has been developed. Preliminary results show marked though transient increases in cats with sepsis and urethral obstruction-associated AKI, and expression in injured tubules. Although initial data indicating that the LFA is sensitive and specific for KIM-1 in cats with AKI are promising, values associated with different types of injury, urine collection, urine storage and specific gravity need to be investigated.

Assessment of the association between diabetes mellitus and chronic kidney disease in adult cats

Background

Diabetes mellitus is the main cause of chronic kidney disease (CKD) in humans. The relationship between the 2 diseases in cats is unclear.

Objective

To assess the association between diabetes and CKD in a population of adult cats.

Animals

Five hundred sixty‐one cats that attended 2 veterinary centers in Gran Canaria, Spain, between 2014 and 2016.

Methods

Medical records were retrospectively reviewed. Cats aged 3 years or older, with sufficient data to define whether or not they had diabetes and CKD, were selected. Cats in critical condition, with dehydration or potential causes of prerenal azotemia and those treated with nephrotoxic drugs were excluded. Diagnosis of CKD was established when creatinine concentrations were >2 mg/dL, or serum creatinine 1.6‐2 mg/dL and urine specific gravity <1.035, or serum creatinine 1.6‐2 mg/dL and urine protein/creatinine ratio >0.4. Factors associated with CKD were identified through multivariate logistic regression analyses.

Results

Sixty‐seven (11.9%) cats had CKD and 16 (2.9%) cats had diabetes. Sixty cats without diabetes (11%) and 7 with diabetes (44%) had CKD. Among the latter, both conditions were diagnosed simultaneously in 6 cases, whereas diabetes preceded CKD in the other. Multivariate analysis showed that diabetes was significantly associated with CKD (odds ratio = 4.47; 95% confidence interval, 1.51‐13.28; P = .007). Other variables associated with CKD were age and mixed breed.

Conclusions and Clinical Importance

After adjusting for age, this study showed an association between diabetes and CKD in adult cats.

Chronic kidney disease in cats attending primary care practice in the UK: a VetCompassTM study

Chronic kidney disease (CKD) is a frequent diagnosis in cats attending primary care practice and the most frequent cause of death in cats aged over five years, yet there is limited published research for CKD in cats attending primary care practice. This study aimed to estimate the prevalence of CKD and investigate risk factors for diagnosis and survival of cats diagnosed with CKD in UK primary care practices. The study included cats attending VetCompass^TM practices from January 1, 2012 to December 31, 2013. A nested case-control and cohort study were undertaken. From 353,448 cats attending 244 clinics, the prevalence of CKD was estimated as 1.2 per cent (95 per cent CI 1.1 per cent to 1.3 per cent). Most cats with CKD had clinical signs at diagnosis (66.6 per cent). Few cats underwent investigations or monitoring of serum creatinine (32.6 per cent), urine protein:creatinine ratio (14.9 per cent) or blood pressure measurement (25.6 per cent). A proprietary renal diet was the most frequently prescribed management (63.8 per cent). Median survival time following diagnosis was 388 days (IQR 88-1042 days). This study provides generalisable evidence from the wider cat population to aid veterinarians in improved diagnosis and management of CKD that can benefit the health and welfare of cats with CKD in the UK.

Chronic Renal Changes After a Single Ischemic Event in an Experimental Model of Feline Chronic Kidney Disease

Previous work demonstrated renal fibrosis 70 days after a single unilateral in vivo renal ischemic event, but changes associated with a single episode of renal ischemia past this time are unknown. In this study, we evaluated renal function and structural changes 6 months after a 90-minute in vivo unilateral renal ischemic event. Six adult female cats underwent unilateral renal ischemia and renal function was followed for 6 months, at which time the kidneys were evaluated by histology and histomorphometry. Over time, there was a significant reduction in the glomerular filtration rate and an elevation of serum creatinine of 31% and 42%, respectively. All cats had tubulointerstitial lesions characterized by segmental interstitial inflammation, tubular atrophy, and interstitial fibrosis. Unlike short-term studies, ischemic kidneys had variable numbers of obsolescent glomeruli, consistent with the development of atubular glomeruli and subsequent ischemic glomerulosclerosis. Chronic changes associated with acute renal ischemia may include loss of function and glomerulosclerosis.

Safety and efficacy of orally administered telmisartan for the treatment of systemic hypertension in cats: Results of a double-blind, placebo-controlled, randomized clinical trial

BACKGROUND

Information regarding the efficacy of telmisartan for feline systemic arterial hypertension is limited.

OBJECTIVES

To evaluate the safety and efficacy of PO administered telmisartan solution in hypertensive cats.

ANIMALS

Client-owned cats with indirect systolic arterial blood pressure (SBP) of 160-200 mm Hg, based on multiple measurements.

METHODS

This multicenter trial consisted a 28-day, prospective, randomized, double-blind, placebo-controlled, parallel group, efficacy phase and a 154-day extended-use telmisartan phase. Hypertensive cats were randomly assigned to receive 1.5 mg telmisartan/kg PO q12h for 14 days, followed by 2 mg telmisartan/kg PO q24h, or equivalent volume of placebo. Systolic blood pressure was measured on days 0, 14, and 28. Change in SBP compared to baseline was calculated for days 14 and 28. Telmisartan efficacy was defined as significant decrease in SBP at day 14 compared to placebo and a clinically relevant (>20 mm Hg) decrease in SBP at day 28.

RESULTS

Two-hundred twenty-one cats were included. On day 14, least squares mean (95% confidence interval) SBP decrease was significantly larger in telmisartan-treated (-23.3 mm Hg [-28.2 to -18.3]) versus placebo-treated (-7.5 mm Hg [-13.6 to -1.5]) cats (P = .0005). On day 28, telmisartan treatment resulted in a clinically relevant SBP decrease (-23.9 mm Hg [-27.8 to -20.0]), whereas placebo did not (-11.6 mm Hg [-17.4 to -5.9 mm Hg]). The decrease in SBP persisted over the 6-month trial in telmisartan-treated cats.

CONCLUSIONS AND CLINICAL IMPORTANCE

Telmisartan significantly decreased SBP to a clinically relevant extent and was well tolerated in hypertensive cats.

The renin-angiotensin-aldosterone system and its suppression

Chronic activation of the renin-angiotensin-aldosterone system (RAAS) promotes and perpetuates the syndromes of congestive heart failure, systemic hypertension, and chronic kidney disease. Excessive circulating and tissue angiotensin II (AngII) and aldosterone levels lead to a pro-fibrotic, -inflammatory, and -hypertrophic milieu that causes remodeling and dysfunction in cardiovascular and renal tissues. Understanding of the role of the RAAS in this abnormal pathologic remodeling has grown over the past few decades and numerous medical therapies aimed at suppressing the RAAS have been developed. Despite this, morbidity from these diseases remains high. Continued investigation into the complexities of the RAAS should help clinicians modulate (suppress or enhance) components of this system and improve quality of life and survival. This review focuses on updates in our understanding of the RAAS and the pathophysiology of AngII and aldosterone excess, reviewing what is known about its suppression in cardiovascular and renal diseases, especially in the cat and dog.