Anemia of renal disease: what it is, what to do and what's new

Anaemia in South American camelids - an overview of clinical and laboratory diagnostics

South American camelids (SACs) play an increasing role in veterinary care in Europe. Many alpacas or llamas presented to veterinarians suffer from anaemia, regularly with a packed cell volume (PCV) below 0.10 l/l, which is a life-threatening condition for the animals. This review article presents clinical and laboratory diagnostic tools for the diagnosis of anaemia in SACs. Clinical identification of anaemic animals can be performed by assessing the FAMACHA© score and the Body Condition Score (BCS), since anaemia in alpacas and llamas correlates with pale mucous membranes and a lowered BCS. Haematological examination of a blood sample can provide a more differentiated diagnosis of anaemia in SACs. A common finding is regenerative anaemia with an increased number of reticulocytes that is often caused by blood loss due to Haemonchus contortus. Changes in a blood smear from an alpaca or llama with regenerative anaemia may include normoblasts (nucleated red blood cells), anisocytosis, poikilocytosis, polychromasia, Howell-Jolly bodies or basophilic stippling. Furthermore, non-regenerative anaemia, often caused by trace element deficiency or cachexia, can also occur.

Pharmacodynamic effects of molidustat on erythropoiesis in healthy cats

BACKGROUND

Inhibition of hypoxia-inducible factor prolyl hydroxylase (HIF-PH) stimulates erythropoiesis in rats, dogs, monkeys, and humans.

HYPOTHESIS/OBJECTIVE

Determine if molidustat, a novel HIF-PH inhibitor, stimulates erythropoiesis in healthy cats.

ANIMALS

Seventeen healthy adult laboratory cats.

METHODS

Randomized, placebo-controlled study. Cats were treated PO once daily with suspensions of 0 (Group 1; n = 6), 5 (Group 2; n = 6), or 10 (Group 3; n = 5) mg/kg of molidustat. Effects on red blood cell parameters, reticulocyte indices and plasma erythropoietin (EPO) concentrations were evaluated. Molidustat treatment was stopped when hematocrit (HCT) exceeded 60%.

RESULTS

Compared to placebo, a significant increase in mean HCT was evident starting on Day 14 (Group 2:54.4% vs 40.3%, P < .001, 95% confidence interval [CI] for the difference [8.95-19.28]; Group 3:61.2% vs 40.3%, P < .001, 95% CI [15.48-26.43]) and remained significantly higher for the entire treatment period. In molidustat-treated groups, HCT exceeded 60% on Day 21 (Group 2) and Day 14 (Group 3). Mean HCT in molidustat-treated cats returned to within the reference range (29%-45%) after Day 56 and was numerically comparable to placebo from Day 70 onwards. Red blood cell count and hemoglobin concentrations followed a similar pattern as HCT. Mean EPO concentrations significantly increased after molidustat administration on all assessment days. Molidustat treatments were well tolerated.

CONCLUSIONS AND CLINICAL IMPORTANCE

Marked erythropoietic effects were identified after daily administration of molidustat to healthy cats and additional studies are warranted to evaluate the effects in anemic cats.

Use of molidustat, a hypoxia-inducible factor prolyl hydroxylase inhibitor, in chronic kidney disease-associated anemia in cats

BACKGROUND

Erythropoietic effects of molidustat, a hypoxia-inducible factor prolyl hydroxylase (HIF-PH) inhibitor, were previously demonstrated in healthy cats.

OBJECTIVE

To evaluate the safety and erythropoietic effects of daily PO administration of molidustat in anemic cats with chronic kidney disease (CKD).

ANIMALS

Twenty-one client-owned CKD cats (4-17 years old) with anemia.

METHODS

Multicenter field study; randomized, masked, and placebo-controlled. Cats were treated PO once daily for 28 days with suspensions of control product (CP; n = 6) or 5 mg/kg of molidustat (n = 15). Hematocrit (HCT) was evaluated at weekly intervals. Individual cat treatment success was defined as a ≥4% point increase in HCT compared to baseline.

RESULTS

Control group mean HCT remained low throughout the study (20.1%-23.4%). Mean HCT of molidustat-treated cats increased weekly, and a significant increase compared to baseline (23.6%) was first observed on Day 21 (27.3%; P < .001; 95% confidence interval [CI], 1.69-5.67). Compared to CP group, mean HCT was significantly higher on Day 21 (27.3% vs 20.1%; P < .001; 95% CI, 2.91-10.75) but not significantly higher on Day 28 (27.8% vs 23.4%; P = .06; 95% CI, -0.23 to 9.88). The number of individual treatment successes on Day 28 was higher among remaining molidustat-treated cats (7/14) compared to remaining control cats (1/5), but there was no significant difference between groups.

CONCLUSIONS AND CLINICAL IMPORTANCE

Daily PO molidustat administration may stimulate a clinically relevant erythropoietic response in anemic cats with CKD. This HIF-PH inhibitor may be an alternative for managing anemia in cats compared to recombinant EPO treatment.

Clinical management of feline chronic kidney disease in Portugal: a questionnaire-based study

OBJECTIVES

The aim of the study was to characterise the clinical management of feline chronic kidney disease (CKD) by veterinary practitioners in Portugal.

METHODS

A questionnaire-based study was designed to be completed by all veterinarians who had diagnosed and treated at least one case of feline CKD in the previous year.

RESULTS

A total of 409 veterinary practitioners responded to the questionnaire, with approximately half of them diagnosing 2-5 cases of feline CKD per month (n = 219, 53.5%). Although a high proportion of these reported using the guidelines published by the International Renal Interest Society (n = 379, 92.7%), only 19.1% (n = 78) systematically performed systolic blood pressure (SBP) measurements in all of their patients. A renal diet was advised by almost all respondents (n = 406, 99.3%), but 36.9% (n = 150) of them considered that it represented less than 75% of the daily food intake for most of their patients. This dietary intervention was often prescribed regardless of stage (n = 298, 73.4%) and without a proper gradual diet transition. Appetite stimulants were frequently prescribed (n = 366, 89.5%), as well as a calcium channel blocker (n = 171, 41.8%) and an angiotensin-converting enzyme inhibitor (n = 245, 59.9%) to control systemic hypertension and proteinuria, respectively. Prescription of a phosphate binder was also common (n = 311, 76.0%). Regarding monitoring, 70.9% (n = 290) recommended that stable patients be reassessed every 2-3 months or more frequently, but only 35.7% (n = 146) were able to comply with this periodicity due to owners' constraints.

CONCLUSIONS AND RELEVANCE

The findings showed that although most survey respondents are aware of international guidelines for the clinical management of cats with CKD, the SBP measurement still needs to be more systematic to allow proper substaging and detection of systemic hypertension. The monitoring frequency was lower than recommended. Furthermore, the introduction of a renal therapeutic diet should be refined to improve its acceptance rate.

Retrospective study of canine blood xenotransfusion compared with type-matched feline blood allotransfusion to cats: indications, effectiveness, limitations and adverse effects

OBJECTIVES

Xenotransfusion is the transfusion of blood from one species to another. With varying availability of allogenic feline blood (AFB) and in emergency conditions, circumstances occur when canine blood is transfused to cats. This study aimed to characterise the indications, effectiveness, limitations, and acute and late transfusion-related adverse effects of canine blood xenotransfusion compared with matched AFB to anaemic cats, and their survival and longer-term outcome.

METHODS

This retrospective study (2013-2020) examined cats receiving canine blood xenotransfusions or AFB.

RESULTS

The study included 311 cats (xenotransfusion [X-group], n = 105; allotransfusion [A-group], n = 206). Xenotransfusion was more frequent among cats sustaining haemorrhage than in those with haemolysis (P <0.01) or hypoproliferative anaemia (P <0.001). Financial constraints were the most common reason to elect xenotransfusion (49%). The post-transfusion mean packed cell volume was higher (P <0.001) in the X-group (22%) compared with the A-group (18%), and also higher (P <0.001) at 48-96 h post-transfusion (23% vs 18%, respectively). Transfusion-related adverse effects (TRAEs) were more frequent (P = 0.001) in the X-group (37.1%) compared with the A-group (19.4%), as were delayed haemolytic transfusion reactions (85% vs 42.5%, respectively; P <0.001). Acute transfusion reactions (ATRs) were more frequent (P <0.001) in the A-group (60%) compared with the X-group (20%). TRAEs were unassociated with survival to discharge. The survival to discharge rate of the X-group (55%) was lower (P = 0.007) than in the A-group (73%), while post-discharge survival rates to 30 days of cats surviving to discharge were 90% and 88%, respectively (P = 0.85).

CONCLUSIONS AND RELEVANCE

Canine blood xenotransfusions to cats might save lives in emergency conditions when AFB is unavailable or blood typing is infeasible. The survival to discharge rate of the X-group was lower than that of the A-group. The longer-term survival rate of cats administered xenotransfusions and surviving to discharge from the hospital was good.

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.

Diagnostic value of reticulocyte indices for the assessment of the iron status of cats with chronic kidney disease

Background

Reticulocyte indices have been suggested as alternatives to transferrin saturation (TSAT) for iron status assessment in humans and dogs but they have not been evaluated thoroughly in cats.

Objectives

To assess the value of the reticulocyte indices for the diagnosis of iron deficiency in cats with chronic kidney disease (CKD) and chronic hematuria associated with subcutaneous ureteral bypasses (SUBs).

Animals

Sixty‐four cats: 16 healthy, 14 CKD without SUB, and 34 CKD with SUB.

Methods

Prospective observational cross‐sectional study of cats presented for routine nephrology visits. Primary outcomes included assessment of the diagnostic values of erythrocyte indices (mean corpuscular volume, hemoglobin, and hemoglobin concentration: MCV, MCH, and MCHC) and reticulocyte indices (mean corpuscular volume, MCVr; corpuscular hemoglobin, CHr), using TSAT as reference.

Results

Iron deficiency was diagnosed in 9/64 cats (14%). A receiver‐operating characteristic curve analysis yielded a moderate discriminatory value for CHr in this diagnosis: area under the curve [AUC] = .75 (95% confidence interval, 0.48‐0.89); P = .006; sensitivity 67%, specificity 82% for a cutoff of 15.9 pg. This compared favorably to MCVr (AUC = .63; P = .29), MCV (AUC = .58; P = .45), MCH (AUC = .64; P = .19), and MCHC (AUC = .7; P = .03).

Conclusion and Clinical Importance

CHr added moderate value to the diagnosis of iron deficiency in cats with CKD.

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.

Evaluation of Chronic Kidney Disease Progression in Dogs With Therapeutic Management of Risk Factors

This research was performed to describe the characteristics of the progression of naturally occurring chronic kidney disease (CKD) in dogs, together with the management of identified risk factors, following the International Renal Interest Society recommendations. Dogs diagnosed and staged with CKD, and with a longitudinal follow-up from the moment of diagnosis of up to a maximum of 730 days, were included. A total of 545 dogs that presented risk factors for the development of CKD were analyzed, out of which 36 met the inclusion criteria. Advanced age was identified in 80.6% of cases. Initiation risk factors were represented by inflammatory/infectious diseases, history of anesthetic-surgical procedures, heart disease, neoplasms, endocrinopathies, and exposure to nephrotoxic drugs. During the follow-up period, progression of CKD was identified in 47.2% of the cases, being more salient in advanced stages. Serum symmetric dimethyl arginine (SDMA) was the only glomerular filtration rate (GFR) marker which displayed differences among studied times during early stages of CKD, associated with the disease progression and decline of renal function. A significant difference between the survival curves in early and advanced CKD stages was observed. The factors related to decreased survival were hyperphosphatemia, anemia, and low body condition score (BCS). No differences were found between the presence of arterial hypertension and renal proteinuria and decreased survival. Furthermore, CKD diagnosis based on the persistent finding of abnormalities in early disease markers, such as serum symmetric dimethyl arginine increase and/or renal proteinuria, and timely therapeutic management of risk factors, allowed for CKD stabilization, reducing progression to advanced stages, and favoring higher survival rates.

Polycystic kidney disease concurrent with feline parvovirus and bacterial infections in domestic shorthair cat: a case report

Feline polycystic kidney disease (PKD) is an inherited disorder caused by the mutation of PKD1 gene that eventually lead to the development of chronic kidney disease. The latter condition causes hypertension and eventually progress into congestive heart failure. Feline parvovirus (FPV) is a highly contagious and often fatal disease infecting cats and other members of Felidae. An 8-month-old female domestic shorthair cat was presented with complaint of wound dehiscence a day after ovarian hysterectomy procedure. The wound at the suture site appeared necrotic, purulent with foul smell. The cat was found to have diarrhoea during the fixation of suture breakdown and, later, was tested positive with parvovirus infection. Complete blood count revealed anaemia, neutrophilia, lymphopenia and thrombocytosis. Biochemistry profiles showed hypoproteinaemia and elevated of urea and creatinine. The cat was hospitalised, and symptomatic treatments were given. During hospitalisation, the cat showed symptoms of polydipsia and polyuria and found dead 2 days later. Post-mortem findings demonstrated the cat had oral ulceration, thoracic effusion, fibrinopleuropneumonia, pericardial effusion, left ventricular hypertrophy and right ventricular dilation, chronic passive liver congestion, mesenteric lymphadenomegaly, intestinal haemorrhage, adrenomegaly and polycystic kidney. Histopathological evaluation revealed fibrinous pleuropneumonia, pulmonary atelectasis, emphysema and oedema, hypertrophic cardiomyopathy, hepatic necrosis, splenic necrosis, intestinal necrosis, renal necrosis and renal polycystic. Staphylococcus aureus and Escherichia coli were isolated from bronchus swab and intestinal segment, respectively. Polymerase chain reaction (PCR) revealed parvovirus infection. The cat was definitely diagnosed with polycystic kidney disease concurrent with parvoviral and secondary bacterial infections.

Non-Renal Lesions of Uraemia in Domestic Cats

Uraemia is a clinical syndrome caused by an increase in uraemia-associated toxins in the bloodstream as a consequence of intrinsic kidney or lower urinary tract diseases. Cats seem to be more affected by urinary tract diseases than dogs, particularly considering that chronic kidney disease (CKD) is one of the most important conditions in cats. Considering the lack of information on the systemic lesions of uraemia in cats, the aim of this study was to investigate the prevalence and clinical and pathological aspects of non-renal lesions in uraemic cats, with special attention to the differences between cats and dogs. Cats necropsied between 2000 and 2019 (n = 1,330) were investigated for urinary tract diseases and non-renal lesions of uraemia. The prevalence of uraemic cats with non-renal lesions (n = 78) was 5.8%. Adult, elderly and male animals were predominantly affected. Anorexia, apathy and vomiting were the most common clinical signs and CKD was observed in the majority of uraemic cats. Pulmonary oedema was the most frequent non-renal lesion identified. In contrast with previous reports, haemorrhagic and ulcerative gastritis was frequently observed, whereas soft tissue mineralization and parathyroid hyperplasia were uncommon features. Fibrous osteodystrophy was not observed. Cats with urinary tract diseases did not have as wide a variety of non-renal uraemic lesions as uraemic dogs and multisystemic manifestation of uraemia was observed in only 24.4% of cases.

Variability in the cleavage of exosome-associated transferrin receptor questions the utility of clinically useful soluble transferrin receptor assays for dogs, cats, and horses

Whole transferrin receptor (TfR) is present in reticulocyte exosomes. Soluble transferrin receptor (sTfR) is cleaved from whole TfR in human plasma, with the remnant cytoplasmic domain (cTfR) remaining membrane associated. In humans, sTfR is a biomarker that can detect iron deficiency in the presence of inflammatory disease. This condition is still a diagnostic dilemma in veterinary species. We aimed to (1) confirm the presence of exosomes and exosome-associated TfR in the serum of dogs, cats, and horses; and (2) to assess and compare the proportion of cTfR to total (cTfR + whole) in exosomal membranes of healthy and diseased dogs and cats and in healthy horses to indirectly predict their anticipated levels of circulating sTfR. We used discarded serum and whole blood samples from canine and feline patients, separated into healthy and diseased groups based on the health status of each patient, and healthy equine participants from a previous study. Ultracentrifugation, followed in some experiments by OptiPrep discontinuous density gradient fractionation, was used to isolate exosomes. Exosomes and associated TfR were identified using TEM and Western blot for TfR, respectively. Densitometry tracings of Western blots of serum exosomes were used to measure the proportion of cTfR to total TfR. Extracellular vesicles compatible with exosomes were successfully isolated and expressed TfR. The proportion of cTfR in dogs was greater than 50%, indicating that a majority of the whole TfR was cleaved to produce sTfR (and remnant cTfR). There was significant interindividual variation and no significant difference between healthy and diseased animals. The proportion of cTfR in cats was very low at 11%, indicating that very little sTfR was likely produced. There was a small yet significant difference between healthy and diseased cats. Healthy horses do not appear to cleave exosome-associated TfR. Diagnosis of iron deficiency in the presence of inflammatory disease remains a challenge in veterinary medicine. Our results indicate that TfR is poorly or unpredictably cleaved in veterinary species, revealing that there are species differences in exosomal TfR handling. These data suggest that development of an assay for the detection and quantification of sTfR in the species investigated may not be warranted.

Urine hemojuvelin in cats with naturally occurring kidney disease

BACKGROUND

Soluble-type hemojuvelin in serum and urine has been shown to be a biomarker in humans for chronic kidney disease (CKD) and acute kidney injury (AKI). No similar research has been conducted on cats.

OBJECTIVE

Urine hemojuvelin (u-hemojuvelin) can be used as a clinical indicator for cats with various renal diseases.

ANIMALS

Eighteen healthy cats, 10 cats with AKI, 21 cats with acute-on-chronic kidney injury (ACKI), and 45 cats with CKD were enrolled.

METHODS

The expression profile of u-hemojuvelin was assessed by Western blot analysis, whereas the u-hemojuvelin concentration was measured using an in-house sandwich ELISA. Each cat's u-hemojuvelin-to-creatinine ratio (UHCR) also was determined.

RESULTS

Significant differences were found in both u-hemojuvelin concentration and UHCR between the control cats and the other cats (AKI, CKD, ACKI). Both u-hemojuvelin and UHCR had high areas under the receiver operator curve (AUROC) for diagnoses of AKI (u-hemojuvelin, 0.885; UHCR, 0.982), CKD (hemojuvelin, 0.869; UHCR, 0.959), and ACKI (hemojuvelin, 0.910; UHCR, 1). Late stage (International Renal Interest Society, IRIS stages 3 and 4) CKD cats had significantly higher u-hemojuvelin concentration and UHCR than did early stage cats (IRIS stages 1 and 2). Both u-hemojuvelin and UHCR were significantly correlated with high blood urea nitrogen, plasma creatinine, and plasma phosphate concentrations and with low hematocrit (Hct), red blood cell (RBC) count, and plasma albumin concentration. The UHCR values were also significantly correlated with white blood cell count in blood.

CONCLUSION

Both u-hemojuvelin and UHCR potentially can serve as diagnostic indicators for a range of renal diseases in cats.

Feline non-regenerative anemia: Diagnostic and treatment recommendations

PRACTICAL RELEVANCE

Non-regenerative anemia, or anemia with reticulocytopenia, is a daily diagnosis in feline practice.

CLINICAL CHALLENGES

The disease processes underlying non-regenerative anemia are many and diverse. A major diagnostic evaluation may be required to correctly diagnose and treat the underlying cause.

AUDIENCE

All veterinarians caring for cats will face the diagnostic and therapeutic challenge of non-regenerative anemia. Readers will benefit from the review of diagnostic testing and therapeutic options for non-regenerative anemia.

EVIDENCE BASE

This review summarizes the currently available literature informing diagnostic and treatment recommendations related to non-regenerative anemia. The evidence available to support the recommendations in this review is graded as low and includes predominantly expert opinion, case reports and cases series, on which the authors' interpretation/consensus is based.

Placement of subcutaneous ureteral bypasses without fluoroscopic guidance in cats with ureteral obstruction: 19 cases (2014-2016)

Objectives The purpose of this study was to describe the perioperative and postoperative complications as well as short-term and long-term outcomes in cats with ureteral obstructions treated by placement of a subcutaneous ureteral bypass (SUB) device without imaging control. The second objective of this study was to compare cats treated by SUB device with cats treated by traditional surgical intervention. Methods Data were obtained retrospectively from the medical records (2014-2016) of cats that underwent SUB placement (SUB cats) and cats that underwent traditional ureteral surgery (C cats). Results Nineteen SUB devices were placed without fluoroscopic, radiographic or ultrasonographic guidance in 13 cats. Fifteen traditional interventions (ureterotomy and neoureterocystostomy) were performed in 11 cats. Successful placement of the SUB device was achieved in all cats with only one major intraoperative complication (kinking of the kidney catheter) and one minor intraoperative complication (misplacement of the kidney catheter). Eleven SUB cats recovered from the surgical procedure; two SUB cats and three C cats died during the anaesthesia recovery period. Postoperative SUB complications included anaemia (n = 2), urinary tract infection (UTI) (n = 4), non-infectious cystitis (n = 5) and SUB device obstruction (n = 1). Postoperative traditional surgery complications included anaemia (n = 7), UTIs (n = 6), non-infectious cystitis (n = 1), re-obstruction (n = 4) and ureteral stricture (n = 1). Median postoperative duration of hospitalisation (3 days) was significantly shorter for SUB cats than for C cats ( P = 0.013). Ten SUB cats (76.9%) and four C cats (40%) were still alive at a median follow-up of 225 days and 260 days, respectively. Owners were completely (90%) or mostly (10%) satisfied with the SUB device placement. Conclusions and relevance SUB device placement appears to be an effective and safe option for treating ureteral obstruction in cats, and this study has shown that fluoroscopic guidance is not essential in all cases.

Acute-Phase Proteins and Iron Status in Cats with Chronic Kidney Disease

Background

The role of inflammation in the development and progression of chronic kidney disease (CKD) in cats is not well characterized. Hepcidin is a recently discovered acute‐phase protein (APP) that plays an important role in iron metabolism and contributes to the development of anemia in humans with CKD.

Objectives

To compare serum APP concentrations, iron status, and erythropoietin (EPO) concentrations in healthy cats and cats with naturally occurring CKD.

Animals

A total of 18 healthy control cats and 38 cats with CKD.

Methods

Prospective study. After complete physical examination and routine blood analysis, the following tests were performed: serum amyloid A (SAA), haptoglobin (HAP), EPO, serum iron and ferritin concentration as well as total iron‐binding capacity (TIBC). Serum hepcidin‐25 concentration was measured by ELISA kit designed for use in humans.

Results

Mean SAA and hepcidin concentrations were significantly higher and mean total iron and TIBC were significantly lower in the CKD group (P < .05). There was a significant positive correlation between serum creatinine concentration (CRT) and 2 of the APPs (SAA and hepcidin; P < .05). Increases in SAA and hepcidin were associated with decreases in TIBC and hematocrit in the CKD group. Fourteen (37%) of the cats with CKD were anemic, and these cats had significantly lower TIBC (P < .05), suggesting a functional iron deficiency. There was no association between survival time and APP, iron status, or EPO concentrations.

Conclusions

Our data suggest that CKD in cats is associated with systemic inflammation and altered iron metabolism. With further validation in cats, hepcidin assays may help better characterize these relationships.

ISFM Consensus Guidelines on the Diagnosis and Management of Feline Chronic Kidney Disease

PRACTICAL RELEVANCE

Chronic kidney disease (CKD) is one of the most commonly diagnosed diseases in older cats. In most cats, CKD is also a progressive disease and can be accompanied by a wide range of clinical and clinicopathological changes. These ISFM Consensus Guidelines have been developed by an independent panel of clinicians and academics to provide practical advice on the diagnosis and management of this complex disease.

CLINICAL CHALLENGES

Although CKD is a common clinical problem in cats, the manifestations of disease vary between individuals. Thus there is a need for careful and repeat evaluation of cats with CKD and adjustment of therapy according to individual needs. In addition to addressing problems arising from CKD and improving quality of life (QoL) for the patient, therapy may also target slowing the underlying progression of disease and hence prolonging life. While maintaining QoL is of paramount importance in our patients, this can be challenging when multiple therapies are indicated. In some cases it is necessary to prioritise therapy, given an understanding of what is likely to most benefit the individual patient.

EVIDENCE BASE

In preparing these Guidelines, the Panel has carefully reviewed the existing published literature, and has also graded the quality of evidence for different interventions to help to provide practical recommendations on the therapeutic options for feline CKD. This is a field of veterinary medicine that has benefited from some excellent published clinical research and further research findings will undoubtedly modify the recommendations contained in these Guidelines in the future.

Chronic Kidney Disease in Aged Cats: Clinical Features, Morphology, and Proposed Pathogeneses

Chronic kidney disease (CKD) is the most common metabolic disease of domesticated cats, with most affected cats being geriatric (>12 years of age). The prevalence of CKD in cats exceeds that observed in dogs, and the frequency of the diagnosis of CKD in cats has increased in recent decades. Typical histologic features include interstitial inflammation, tubular atrophy, and fibrosis with secondary glomerulosclerosis. In contrast to people and dogs, primary glomerulopathies with marked proteinuria are remarkably rare findings in cats. Although a variety of primary renal diseases have been implicated, the disease is idiopathic in most cats. Tubulointerstitial changes, including fibrosis, are present in the early stages of feline CKD and become more severe in advanced disease. A variety of factors-including aging, ischemia, comorbid conditions, phosphorus overload, and routine vaccinations-have been implicated as factors that could contribute to the initiation of this disease in affected cats. Factors that are related to progression of established CKD, which occurs in some but not all cats, include dietary phosphorus intake, magnitude of proteinuria, and anemia. Renal fibrosis, a common histologic feature of aged feline kidneys, interferes with the normal relationship between peritubular capillaries and renal tubules. Experimentally, renal ischemia results in morphologic changes similar to those observed in spontaneous CKD. Renal hypoxia, perhaps episodic, may play a role in the initiation and progression of this disease.

Hospital-acquired Anemia in Critically Ill Dogs and Cats: A Multi-Institutional Study

BACKGROUND

Hospital-acquired anemia is commonly described in people but limited information currently is available regarding its prevalence in animals.

HYPOTHESIS/OBJECTIVES

Assess the prevalence of hospital-acquired anemia in hospitalized critically ill dogs and cats, and examine its relationship with phlebotomy practices, transfusion administration, and survival to discharge.

ANIMALS

Eight hundred and fifty-one client-owned animals (688 dogs and 163 cats).

METHODS

A multicenter, observational study was conducted in which packed cell volume (PCV) was recorded at the time of admission and on subsequent hospitalization days. Signalment, number of blood samples obtained, underlying disease, whether or not blood products were administered, duration of hospitalization, and survival to discharge were recorded.

RESULTS

Admission anemia prevalence was 32%, with overall prevalence during the hospitalization period of 56%. The last recorded PCV was significantly lower than the admission PCV for both dogs (admission PCV, 42% [range, 6-67%]; last recorded PCV, 34% [range, 4-64%], P < .0001) and cats (admission PCV, 31% [range, 6-55%]; last recorded PCV, 26% [range, 10-46%], P < .0001). Patients that developed anemia had significantly more blood samples obtained (nonanemic, 5 blood samples [range, 2-54]; anemic, 7 blood samples [range, 2-49], P < .0001). Hospitalized cats were significantly more likely to develop anemia compared to dogs (P < .0001), but anemic dogs were significantly less likely to survive to discharge (P = .0001). Surgical patients were at higher risk of developing hospital-acquired anemia compared to medical patients (OR, 0.63; 95% CI, 0.4-0.9; P = .01).

CONCLUSIONS AND CLINICAL RELEVANCE

Hospital-acquired anemia occurred frequently, especially in surgical patients. Additional studies focused on the direct effect of phlebotomy practices on the likelihood of anemia development in hospitalized animals are warranted.

Iron Status of Cats with Chronic Kidney Disease

BACKGROUND

Iron deficiency is a proposed mechanism for the anemia that occurs in cats with chronic kidney disease (CKD). Minimal research investigating the iron status of these cats has been performed.

OBJECTIVE

To compare indicators of iron status in cats with CKD versus healthy cats and cats with nonrenal illness (NRI). To compare indicators of iron status in anemic versus nonanemic cats with CKD.

ANIMALS

Thiry-nine client or employee owned healthy cats, 40 cats with CKD and 34 cats with NRI included.

METHODS

Exclusion criteria included prior iron or erythropoiesis stimulating agent administration, blood transfusion, or concurrent CKD and NRI. Complete blood counts, serum chemistries, serum iron concentrations, total iron binding capacity (TIBC), and ferritin concentrations were measured and percent transferrin saturation (TSAT) calculated on all cats. Data were analyzed using nonparametric statistical testing.

RESULTS

No statistically significant differences were detected among groups for iron concentration (P = .50), ferritin concentration (P = .47), or TSAT (P = .19). TIBC was significantly lower in CKD (median 262 μg/dL; IQR 233-302; range 165-488) versus healthy cats (median 316 μg/dL; IQR 272-345, range 196-464); (P = .0030). When comparing anemic (hemoglobin <9.5 g/dL) versus nonanemic cats with CKD, TSAT was significantly lower (P = .033) in anemic (median 20.2%; IQR 17.8-34.5; range 17.6-35.9) compared to nonanemic (median 29.0%; IQR 25.5-44.1; range 11.5-94.4). No statistically significant differences found for ferritin concentration (P = .94), iron concentration (P = .21) or TIBC (P = .97).

CONCLUSIONS AND CLINICAL IMPORTANCE

These results indicate that an iron deficient state exists in anemic cats with CKD and is more likely functional rather than absolute.

Cardiovascular-renal axis disorders in the domestic dog and cat: a veterinary consensus statement

OBJECTIVES

There is a growing understanding of the complexity of interplay between renal and cardiovascular systems in both health and disease. The medical profession has adopted the term "cardiorenal syndrome" (CRS) to describe the pathophysiological relationship between the kidney and heart in disease. CRS has yet to be formally defined and described by the veterinary profession and its existence and importance in dogs and cats warrant investigation. The CRS Consensus Group, comprising nine veterinary cardiologists and seven nephrologists from Europe and North America, sought to achieve consensus around the definition, pathophysiology, diagnosis and management of dogs and cats with "cardiovascular-renal disorders" (CvRD). To this end, the Delphi formal methodology for defining/building consensus and defining guidelines was utilised.

METHODS

Following a literature review, 13 candidate statements regarding CvRD in dogs and cats were tested for consensus, using a modified Delphi method. As a new area of interest, well-designed studies, specific to CRS/CvRD, are lacking, particularly in dogs and cats. Hence, while scientific justification of all the recommendations was sought and used when available, recommendations were largely reliant on theory, expert opinion, small clinical studies and extrapolation from data derived from other species.

RESULTS

Of the 13 statements, 11 achieved consensus and 2 did not. The modified Delphi approach worked well to achieve consensus in an objective manner and to develop initial guidelines for CvRD.

DISCUSSION

The resultant manuscript describes consensus statements for the definition, classification, diagnosis and management strategies for veterinary patients with CvRD, with an emphasis on the pathological interplay between the two organ systems. By formulating consensus statements regarding CvRD in veterinary medicine, the authors hope to stimulate interest in and advancement of the understanding and management of CvRD in dogs and cats. The use of a formalised method for consensus and guideline development should be considered for other topics in veterinary medicine.

A retrospective study of 1,098 blood samples with anemia from adult cats: frequency, classification, and association with serum creatinine concentration

BACKGROUND

Frequency and classification of anemia in terms of regeneration status and erythrocyte indices are not well described in cats.

OBJECTIVE

To determine frequency and regenerative status of anemia in samples from adult cats, to assess the sensitivity and specificity of macrocytosis and hypochromasia for detecting regenerative anemia (RA), and to evaluate the association of anemia with increased serum creatinine concentration (SC).

STUDY POPULATION

Laboratory records from 30,503 blood samples from cats (2003-2011).

METHODS

Clinicopathologic data reviewed retrospectively. Anemia defined as hematocrit (Ht) ≤27%, red blood cell count (RBC) ≤5.5 × 10(6)/μL and hemoglobin (Hb) ≤9.0 g/dL. RA defined by manual absolute reticulocyte count >50 × 10(3)/μL. Macrocytosis was defined as mean corpuscular volume (MCV) >55 fL and hypochromasia as mean corpuscular hemoglobin concentration (MCHC) <31 g/dL. Cutoff for increased serum creatinine concentration was 1.6 mg/dL.

RESULTS

Overall, 1,098 of 30,503 blood samples (3.6%) from cats fulfilled criteria for anemia, 633 of 1,098 (57.7%) classified as nonregenerative (NRA) and 465 of 1,098 (42.3%) as regenerative. RBC, Ht, and Hb were significantly lower in the RA compared to NRA group (P < .05). Sensitivity and specificity of the combined high MCV and low MCHC to detect samples with RA were 19.5 and 90.7%. SC was increased in 572 of the 1,098 anemic samples (52.1%) and in 11,121 of 29,405 of nonanemic samples (37.8%).

CONCLUSIONS AND CLINICAL IMPORTANCE

Majority of anemic samples were classified as NRA. Anemia was more severe in cats with RA. Erythrocyte indices were not sensitive indicators of RA.

Feline CKD: Pathophysiology and risk factors--what do we know?

PRACTICAL RELEVANCE

Chronic kidney disease (CKD) is one of the most frequently encountered disorders in cats, having increased in prevalence in recent decades. Although the underlying cause is rarely identified, the common final outcome of feline CKD is tubulointerstitial fibrosis. Knowledge of CKD pathophysiology is necessary for optimal individualised patient management, especially with regard to diagnosis and treatment of extrarenal complications.

PATIENT GROUP

CKD is most common in senior and geriatric cats, but should be considered in any feline patient with ureterolithiasis, hyperthyroidism, retrovirus infection, systemic hypertension, cardiovascular disease or urinary tract infection.

EVIDENCE BASE

Most of our knowledge of the pathogenesis of CKD is extrapolated from human nephrology and experimental animal studies. There is, therefore, a need for further studies in cats. The prevalence of clinical signs in feline CKD is well documented. Several concurrent diseases associated with CKD have also been reported in cats, especially in the geriatric population, but there is no or only limited published evidence demonstrating a cause-and-effect relationship between most of these conditions and CKD. Studies performed over the past 15 years have nevertheless allowed identification of major risk factors (proteinuria, plasma phosphate and plasma creatinine) influencing the progression of feline CKD.

CLINICAL CHALLENGES

Clinical signs occur in the late stages of renal disease, so populations at higher risk of CKD should be screened routinely. CKD-associated complications (systemic hypertension, secondary renal hyperparathyroidism, hypokalaemia, anaemia, metabolic acidosis) must not be overlooked as they may affect the progression of disease. Disease progression is itself unpredictable and renal function may remain stable for extended periods. Most cats with early CKD do not progress to end-stage CKD before they die.

AUDIENCE

General practitioners play a major role in screening feline patients at risk of development or progression of CKD.

Feline CKD: Diagnosis, staging and screening - what is recommended?

PRACTICAL RELEVANCE

Feline chronic kidney disease (CKD) is frequently encountered by veterinarians. Timely diagnosis and staging may facilitate the initiation of adequate therapy and improve the prognosis for patients.

CLINICAL CHALLENGES

Feline CKD is diagnosed based on the presence of compatible clinical signs and renal azotaemia, which implies that urinalysis (particularly urine specific gravity) is mandatory to confirm the diagnosis. Although the diagnosis of advanced feline CKD and associated complications is usually straightforward, based on complete blood and urine examination, all routine blood and urine tests have their limitations in detecting early CKD. Therefore, diagnosing early or non-azotaemic CKD is much more challenging. Although determination of glomerular filtration rate (GFR) would be ideal to identify early kidney dysfunction, practical limitations hamper its routine use in clinical practice.

PATIENT GROUP

CKD is typically a disease of aged cats, but may affect cats of all ages. Conclusive breed and sex predispositions for feline CKD are not reported.

AUDIENCE

This review is directed at practising veterinarians and provides an overview of the required diagnostic tests, the classification system established by the International Renal Interest Society, and the importance of and possible techniques for early detection of CKD.

EVIDENCE BASE

Staging of cats with CKD is essential as it directs management and provides a prognostic guide. Given that diagnosis at early disease stages is associated with more prolonged survival times, simple, inexpensive and accurate methods for early CKD diagnosis are needed. Techniques currently under investigation include limited sampling strategies to estimate GFR, clearance marker cut-off concentrations to identify cats with low GFR, new indirect GFR markers and urinary biomarkers.

Feline CKD: Current therapies - what is achievable?

PRACTICAL RELEVANCE

Treatment of feline chronic kidney disease (CKD) tends to focus on minimising the adverse effects of reduced renal function, rather than addressing an underlying cause. Despite this, and the progressive nature of CKD, treatment can improve quality of life and enable many cats to have long survival times.

EVIDENCE BASE

Strong evidence supports the provision of renal diets, which are protein and phosphorus restricted; compliance is improved by gradual dietary transition. Additional phosphorus restriction is achieved by the use of phosphate binding agents, although it is unknown if these yield similar survival benefits to those provided by renal diets. Interventions to control hypokalaemia and hypertension in affected cats are important to prevent serious complications. Administration of benazepril to cats with proteinuric kidney disease has been shown to significantly improve their appetite but not their survival. As CKD progresses, many cats will benefit from treatment to control clinical signs of uraemic gastroenteritis and anaemia.

A lentiviral gene therapy strategy for the in vitro production of feline erythropoietin

Nonregenerative anemia due to chronic renal failure is a common problem in domestic cats. Unfortunately, administration of recombinant human erythropoietin often only improves anemia temporarily due to antibody development. In this in vitro study, feline erythropoietin cDNA was cloned from feline renal tissue and utilized in the construction of a replication-defective lentiviral vector. The native recombinant feline erythropoietin (rfEPO) sequence was confirmed by sequencing. Upon viral vector infection of human 293H cells, Crandall Renal Feline Kidney cell line and primary feline peripheral blood mononuclear cells, bioactive rfEPO protein was produced. The presence of cellular rfEPO cDNA was confirmed by standard PCR, production of abundant rfEPO mRNA was confirmed by real-time PCR, and secretion of rfEPO protein was demonstrated by Western blot analyses, while rfEPO protein bioactivity was confirmed via an MTT proliferation bioassay. This in vitro study demonstrates the feasibility of a replication-defective lentiviral vector delivery system for the in vitro production of biologically active feline erythropoietin. Anemic cats with chronic renal failure represent a potential in vivo application of a lentiviral gene therapy system.

Erythropoietin: new directions for the nervous system

New treatment strategies with erythropoietin (EPO) offer exciting opportunities to prevent the onset and progression of neurodegenerative disorders that currently lack effective therapy and can progress to devastating disability in patients. EPO and its receptor are present in multiple systems of the body and can impact disease progression in the nervous, vascular, and immune systems that ultimately affect disorders such as Alzheimer's disease, Parkinson's disease, retinal injury, stroke, and demyelinating disease. EPO relies upon wingless signaling with Wnt1 and an intimate relationship with the pathways of phosphoinositide 3-kinase (PI 3-K), protein kinase B (Akt), and mammalian target of rapamycin (mTOR). Modulation of these pathways by EPO can govern the apoptotic cascade to control β-catenin, glycogen synthase kinase-3β, mitochondrial permeability, cytochrome c release, and caspase activation. Yet, EPO and each of these downstream pathways require precise biological modulation to avert complications associated with the vascular system, tumorigenesis, and progression of nervous system disorders. Further understanding of the intimate and complex relationship of EPO and the signaling pathways of Wnt, PI 3-K, Akt, and mTOR are critical for the effective clinical translation of these cell pathways into robust treatments for neurodegenerative disorders.

Chronic kidney disease in dogs and cats

Chronic kidney disease (CKD) occurs commonly in older dogs and cats. Advances in diagnostics, staging, and treatment are associated with increased quality and quantity of life. Dietary modification has been shown to increase survival and quality of life and involves more than protein restriction as diets modified for use with CKD are lower in phosphorous and sodium, potassium and B-vitamin replete, and alkalinizing, and they contain n3-fatty acids. Additionally, recognition and management of CKD-associated diseases such as systemic arterial hypertension, proteinuria, and anemia benefit patients. This article summarizes staging and management of CKD in dogs and cats.