Characterization of kidney damage using several renal biomarkers in dogs with naturally occurring heatstroke

Assessment of cell cycle arrest biomarkers and neutrophil gelatinase-associated lipocalin to distinguish acute kidney injury from other diseases in dogs

BACKGROUND

Cell cycle arrest biomarkers (tissue inhibitor of metalloproteinase-2 [uTIMP-2] and insulin-like growth factor binding protein 7 [uIGFBP7]), and neutrophil gelatinase-associated lipocalin (NGAL) variables are valuable biomarkers for early diagnosis of acute kidney injury (AKI) in people.

OBJECTIVES

To evaluate uTIMP-2, uIGFBP7, fractional excretion of NGAL (FeNGAL), and urinary to serum NGAL ratio (u/sNGAL) in healthy dogs, dogs with AKI, dogs with chronic kidney disease (CKD), and critically ill (CI) dogs.

ANIMALS

Forty-two client-owned dogs (healthy, n = 10; AKI, n = 11; CKD, n = 11; CI, n = 10).

METHODS

Prospective, observational study. After assessment of routine renal biomarkers, stress (uTIMP-2, uIGFBP7) and damage (NGAL) biomarkers were measured, using ELISA kits, and normalized to urinary creatinine (uCr).

RESULTS

Normalized uTIMP-2 and [uTIMP-2] × [uIGFBP7]/uCr were significantly higher in the AKI group (median 151.9 [range, 2.2-534.2] and 62.9 [1.1-266.8] pg/mL respectively), compared to healthy dogs (0.3 [0.2-74.7]; P < .001 and 0.16 [0.1-58.1] pg/mL; P < .001), dogs with CKD (0.7 [0.3-742.5]; P = .04 and 0.37 [0.2-180.1] pg/mL; P = .03) and CI dogs (1.9 [0.2-37.0]; P = .03 and 0.8 [0.1-16.1] pg/mL; P = .02). Fractional excretion of NGAL was significantly higher in dogs with AKI (54.17 [7.93-155.32] %), than in healthy (0.03 [0.01-0.21] %; P < .001) and CI dogs (3.05 [0.05-28.86] %; P = .02).

CONCLUSIONS AND CLINICAL IMPORTANCE

Normalized uTIMP-2, [uTIMP-2] × [uIGFBP7]/uCr, and FeNGAL can be valuable renal biomarkers for early diagnosis of AKI in dogs.

Early Detection of Chronic Kidney Disease Using Plasma Neutrophil Gelatinase-Associated Lipocalin and Kidney Injury Molecule-1 in Small-Breed Dogs: A Retrospective Pilot Study

Multiple diagnostic modalities are urgently needed to identify early-stage kidney diseases. Various molecules have been investigated; however, most studies have focused on identifying specific biomarkers in urine. Considering that assessing the symmetrical dimethylarginine (SDMA) plasma concentration is more suitable as an early diagnostic test for chronic kidney disease (CKD) in routine veterinary practice, we aimed to investigate the clinical usefulness of plasma neutrophil gelatinase-associated lipocalin (pNGAL) and plasma kidney injury molecule-1 (pKIM-1) concentrations for CKD detection in small-breed dogs. Through a retrospective analysis, we found that numerous clinicopathological data showed a log-normal distribution, even when they satisfied normality tests. Moreover, the log-transformed pNGAL and pKIM-1 concentrations successfully identified CKD International Renal Interest Society (IRIS) stages 1-4 and the risk group with underlying CKD risk factors. Correlation analysis and group comparison of other factors confirmed the possibility of using these two biomarkers for detecting the CKD risk group and IRIS stage 1. Receiver operating characteristic curve analysis revealed that the diagnostic accuracy for discriminating the risk group was superior in the order of pKIM-1, pNGAL, SDMA, and serum creatinine levels. In conclusion, these results suggest that pKIM-1 and pNGAL are possible early or quantifiable markers of insignificant CKD or can be at least used as an adjunct with traditional indicators.

Endotoxic kidney injury in Beagle dogs assessed by serum creatinine and symmetric dimethylarginine, and urinary neutrophil gelatinase-associated lipocalin and clusterin

Sepsis of Gram negative bacterial origin results in lipopolysaccharide-induced endotoxemia. This often leads to acute kidney injury (AKI) and its recognition remains a challenge and delays treatment. As renal damage occurs before a rise in serum creatinine is detected, new early biomarkers of kidney injury need to be explored. The aim of this study was to determine changes in serum parameters of renal function and urine biomarkers of renal injury. This was a descriptive study. Endotoxemia was induced intravenously in six anaesthetized Beagles (T1). To achieve normotension, dogs received fluids (T2), followed by a continuous infusion of noradrenaline and dexmedetomidine or 0.9% NaCl (T3). Ten minutes later, the dogs received fluids (T4) and noradrenaline and dexmedetomidine or 0.9% NaCl in a crossover manner (T5). At each timepoint, blood and urine were collected for serum creatinine, urea, symmetric dimethylarginine, urine protein/creatinine (UPC) ratio, urine neutrophil-gelatinase-associated lipocalin (U-NGAL), U-NGAL/creatinine ratio, urine clusterin (U-clusterin) and U-clusterin/creatinine ratio. Data were analyzed using a mixed-effect model taking into account time and stage of veterinary AKI (VAKI). Three of six dogs had a VAKI stage ≥1; one with anuria and elevated creatinine. Serum creatinine (P < 0.001), U-NGAL/creatinine ratio (P = 0.01) and U-clusterin/creatinine ratio increased over time (P < 0.01). The UPC ratio (mean (range) 0.68 (0.35-2.3) versus 0.39 (0.15-0.71) P < 0.01) and U-NGAL (3164 pg/mL (100-147,555) versus 100 (100-14,524), P = 0.01) were higher in VAKI stage ≥1 versus stage 0, respectively. Endotoxemia induced VAKI stage ≥1 in half of the dogs. Repeated measurement of selected parameters could detect AKI early.

Biological variation of biochemical urine and serum analytes in healthy dogs

BACKGROUND

Biological variation (BV) of urinary (U) biochemical analytes has not been described in absolute terms, let alone as a ratio of the U-creatinine or fractional excretion in healthy dogs. These analytes are potential diagnostic tools for different types of kidney damage and electrolyte disorders in dogs.

OBJECTIVES

We aimed to investigate the BV of specific gravity, osmolality, creatinine, urea, protein, glucose, chloride, sodium, potassium, calcium, and phosphate in urine from healthy pet dogs.

METHODS

Blood and urine samples from 13 dogs were collected once weekly for 8 weeks. Samples were analyzed in duplicate and in randomized order. For each sample, U-analyte and serum concentrations were measured, and U-analyte/U-creatinine and fractional excretion (FE) were calculated. Components of variance, estimated by restricted maximum likelihood, were used to determine within-subject variation (CVI ), between-subject variation (CVG ), and analytical variation (CVA ). Index of individuality (II) and reference change values were calculated.

RESULTS

CVI for all urine analytes varied between 12.6% and 35.9%, except for U-sodium, U-sodium/U-Cr, and FE-sodium, which had higher CVI s (59.5%-60.7%). For U-protein, U-sodium, U-potassium, U-sodium/U-creatinine, FE-urea, FE-glucose, FE-sodium, FE-potassium, and FE-phosphate II were low, indicating that population-based RIs were appropriate. The remaining analytes had an intermediate II, suggesting that population-based RIs should be used with caution.

CONCLUSION

This study presents information on the biological variation of urinary and serum biochemical analytes from healthy dogs. These data are important for an appropriate interpretation of laboratory results.

Biomarkers of heatstroke-induced organ injury and repair

NEW FINDINGS

What is the topic of this review? The status and potential role of novel biological markers (biomarkers) that can help identify the patients at risk of organ injury or long-term complications following heatstroke. What advances does it highlight? Numerous biomarkers were identified related to many aspects of generalized heatstroke-induced cellular injury and tissue damage, and heatstroke-provoked cardiovascular, renal, cerebral, intestinal and skeletal muscle injury. No novel biomarkers were identified for liver or lung injury.

ABSTRACT

Classic and exertional heatstroke cause acute injury and damage across numerous organ systems. Moreover, heatstroke survivors may sustain long-term neurological, cardiovascular and renal complications with a persistent risk of death. In this context, biomarkers, defined as biological samples obtained from heatstroke patients, are needed to detect early organ injury, and predict outcomes to develop novel organ preservation therapeutic strategies. This narrative review provides preliminary insights that will guide the development and future utilization of these biomarkers. To this end, we have identified numerous biomarkers of widespread heatstroke-associated cellular injury, tissue damage and repair (extracellular heat shock proteins 72 and 60, high mobility group box protein 1, histone H3, and interleukin-1α), and other organ-specific biomarkers including those related to the cardiovascular system (cardiac troponin I, endothelium-derived factors, circulation endothelial cells, adhesion molecules, thrombomodulin and von Willebrand factor antigen), the kidneys (plasma and urinary neutrophil gelatinase-associated lipocalin), the intestines (intestinal fatty acid-binding protein 2), the brain (serum S100β and neuron-specific enolase) and skeletal muscle (creatine kinase, myoglobin). No specific biomarkers have been identified so far for liver or lung injury in heatstroke. Before translating the identified biomarkers into clinical practice, additional preclinical and clinical prospective studies are required to further understand their clinical utility, particularly for the biomarkers related to long-term post-heatstroke health outcomes.

Human temperature regulation under heat stress in health, disease, and injury

The human body constantly exchanges heat with the environment. Temperature regulation is a homeostatic feedback control system that ensures deep body temperature is maintained within narrow limits despite wide variations in environmental conditions and activity-related elevations in metabolic heat production. Extensive research has been performed to study the physiological regulation of deep body temperature. This review focuses on healthy and disordered human temperature regulation during heat stress. Central to this discussion is the notion that various morphological features, intrinsic factors, diseases, and injuries independently and interactively influence deep body temperature during exercise and/or exposure to hot ambient temperatures. The first sections review fundamental aspects of the human heat stress response, including the biophysical principles governing heat balance and the autonomic control of heat loss thermoeffectors. Next, we discuss the effects of different intrinsic factors (morphology, heat adaptation, biological sex, and age), diseases (neurological, cardiovascular, metabolic, and genetic), and injuries (spinal cord injury, deep burns, and heat stroke), with emphasis on the mechanisms by which these factors enhance or disturb the regulation of deep body temperature during heat stress. We conclude with key unanswered questions in this field of research.

Evaluation of symmetric dimethylarginine in cats with acute kidney injury and chronic kidney disease

Background

Serum symmetric dimethylarginine (SDMA) concentrations are considered a biomarker for renal dysfunction in dogs and humans with acute kidney injury (AKI). No studies have assessed SDMA in cats with AKI.

Hypothesis/Objectives

SDMA correctly identifies cats with azotemic AKI.

Animals

Fifteen control cats, 22 with novel AKI, 13 with acute on chronic‐AKI (AoC) and 19 with chronic kidney disease (CKD).

Methods

Retrospective study. Cats with azotemia (serum creatinine concentrations >1.7 mg/dL) were defined as having AKI or CKD based on history, clinical signs, clinicopathological findings and diagnostic imaging, and classified using the International Renal Interest Society (IRIS) grading/staging systems. Serum SDMA concentrations were compared between groups with nonparametric methods, and correlations assessed using Spearman's correlation coefficient. Data are presented as median [range].

Results

SDMA concentrations were 11 (8‐21) μg/dL, 36 (9‐170)μg/dL, 33 (22‐75) μg/dL and 25 (12‐69) μg/dL in control, novel AKI, AoC and CKD cats. SDMA concentrations were significantly higher in cats with novel AKI (P < .001), AoC (P < .001) and CKD (P < .01) compared to controls. SDMA concentrations were significantly higher in cats with more advanced AKI (IRIS grade IV‐V) compared to less severe AKI (IRIS grade II). Serum creatinine and SDMA concentrations had a significant correlation in cats with novel AKI (r_s = 0.826, n = 22; P < .001) and a significant correlation when all cats across all 4 groups were considered together (r_s = 0.837, n = 69; P < .001).

Conclusions and Clinical Importance

Serum SDMA concentrations are elevated in cats with established AKI (novel and AoC) and CKD, providing evidence for use of SDMA as a biomarker for AKI in cats.

Heat stroke in dogs: Literature review

Heat stroke is a clinical emergency secondary to a severe temperature increase due to the inefficiencies of heat dissipation mechanisms, causing central nervous system dysfunctions, which may lead to multiple organ dysfunction syndrome. Heat disturbances can be classified as "classic" or "exertional" ones and several predisposing factors are involved in their development. This review provides a broad approach to the pathophysiological mechanisms of this syndrome, and the diagnostic and treatment methods to facilitate their approach in clinical routine and increase the survival rate of patients.

Cystatin C and Iris: Advances in the Evaluation of Kidney Function in Critically Ill Dog

Critically ill hospitalized dogs are subject to certain complications, being acute kidney injury (AKI) a common one. Early diagnosis is crucial, and Cystatin C (CysC) is a reliable and early biomarker. The International Society of Renal Interest (IRIS) states that AKI severity can be assessed by mild changes in creatinine serum levels or reduction of urine output that cannot be considered biomarkers of renal injury but failure or insufficiency. Twenty-eight dogs admitted to the Intensive Care Unit under risk factors for the development of AKI were evaluated. Blood samples were collected for determination of sCr and CysC at admission and after 24, 48, and 72 h. Urine output was measured by daily monitoring, measured by collection in a closed system. The results showed the incidence of AKI was 67.9% based on the IRIS criteria and 78.6% based on cystatin C in critically ill patients' dogs. The measurement of serum cystatin C immediately on admission to the ICU was superior in the early identification of patients with AKI when compared to the IRIS classification and serum creatinine in critically ill dogs.

Prospective evaluation of 5 urinary biomarkers as predictors of acute kidney injury in nonazotemic, hospitalized dogs

BACKGROUND

Early recognition of acute kidney injury (AKI) is hindered by current definitions and use of traditional, insensitive markers.

HYPOTHESIS/OBJECTIVES

Urinary (u) activity of γ-glutamyl transpeptidase (GGT) and alkaline phosphatase (ALP), and concentrations of heat-shock protein 70 (HSP70) and interleukins (ILs) -6 and -18, are predictive biomarkers for AKI and survival.

ANIMALS

Nonazotemic, hospitalized dogs (n = 118) and healthy controls (n = 20).

METHODS

A prospective observational study. Nonazotemic dogs at risk of AKI were recruited and their urinary biomarker concentrations were measured at presentation. Serum creatinine (sCr) and symmetric dimethylarginine (sSDMA) were measured daily until discharge/death.

RESULTS

The overall case fatality rate was 18.6%. Fifteen dogs (12.7%) developed AKI, which was associated with death (relative risk, 3.2; 95% confidence interval [CI], 1.57-6.55). All 5 urinary biomarkers were significantly higher in hospitalized dogs compared to controls, with minimal overlap. uHSP70/uCr, uGGT/uCr, and uIL-6/uCr at presentation were higher in dogs which later developed AKI. Areas under the receiver operator characteristic curve (AUROC) (95% CI) for the 3 biomarkers as predictors of AKI were 0.67 (0.51-0.83), 0.68 (0.55-0.81), and 0.78 (0.65-0.91), respectively. When they were categorically classified as elevated/normal, each additional elevated biomarker increased the odds for AKI (OR, 2.83; 95% CI, 1.23-6.52, P = .01). Agreement between sCr and sSDMA was poor (Cohen's kappa = .071). The AUROC of SDMA at presentation for AKI prediction was 0.73 (0.51-0.95).

CONCLUSIONS AND CLINICAL IMPORTANCE

Kidney injury was common, irrespective of subsequent worsening of azotemia or death. The predictive value of individual urinary biomarkers was reduced by moderate sensitivities and specificities. SDMA showed moderate discriminatory utility for AKI prediction, and often displayed discordant results with sCr.

Prognostic value of plasma exosomal levels of histone H3 protein in patients with heat stroke

Heat stroke (HS) is a condition that can lead to multiple organ dysfunction syndrome and death; however, there is no reliable method for stratifying mortality risk in HS. The abundance of exosomes in the circulation and their contents may be used as potential biomarkers of HS. The present study aimed to examine whether histone H3 levels in plasma exosomes could be used to determine HS prognosis. Blood samples were collected from patients with HS (36 survivors and 8 non-survivors) at admission to the intensive care unit and 4 days after admission. Blood samples were additionally collected from 15 healthy volunteers. Plasma exosomes were isolated using high-speed differential centrifugation. Correlation between histone H3 level and organ function and disease severity was examined. The results suggested differential expression and enrichment of histone H3 in the plasma exosomes of patients with HS (survivors, 249.3±04.6; non-survivors, 500.4±216.8; healthy controls, 161.1±52.49 pg/100 µg; P<0.05). The increased expression of histone H3 was associated with increased disease severity and duration. Plasma exosomal levels of histone H3 were significantly correlated with both organ dysfunction and disease severity (P<0.0001) and were significantly different between non-survivors and survivors (area under the receiver operating characteristic curve, 0.9668). A cutoff value of 307 pg/100 µg demonstrated optimized sensitivity (95%) and specificity (91.67%) for predicting mortality risk, suggesting that histone H3 levels in plasma exosomes may be a reliable biomarker for HS prognosis.

Neutrophil Gelatinase-Associated Lipocalin (NGAL) Is Related with the Proteinuria Degree and the Microscopic Kidney Findings in Leishmania-Infected Dogs

Early diagnosis of renal damage in Leishmania infected dogs may allow appropriate treatments and prevent some deaths. This study investigates neutrophil gelatinase-associated lipocalin (NGAL) as a biomarker of kidney disease in dogs experimentally infected with Leishmania infantum. Serum, urine, and kidney samples were collected from 30 infected beagle dogs and six uninfected control dogs. Based on proteinuria and azotemia values, dogs were initially classified. NGAL was measured in urine and serum samples. Then, the urinary NGAL to creatinine ratio (uNGAL/C) was calculated. Kidney samples were taken for histopathological studies, and the dogs were classified according to the severity of glomerular and tubulointerstitial lesions. In Leishmania-infected dogs, the uNGAL/C was significantly higher in proteinuric non-azotemic dogs compared with non-proteinuric non-azotemic dogs (p = 0.038). Serum NGAL (sNGAL) concentration did not differ between groups. Microscopic studies revealed several degrees of glomerulonephritis and slight focal lymphoplasmacytic interstitial nephritis in 89% and 55% of infected dogs, respectively. Urinary protein to creatinine ratio (UPC) and uNGAL/C were significantly higher in dogs with affected glomeruli compared to infected dogs without renal lesions (p = 0.045 and p = 0.043, respectively). The results show that uNGAL/C correlates with proteinuria and the presence of moderate glomerular lesions in non-azotemic dogs experimentally infected with L. infantum.

Comparison of clinicopathological patterns of renal tubular damage in dogs with acute kidney injury caused by leptospirosis and other aetiologies

In humans, leptospiral acute kidney injury (AKI) is characterised by tubulointerstitial involvement and renal electrolyte losses, impacting clinical presentation and case management. The aim of this study was to evaluate urine chemistry findings in dogs with leptospirosis in order to identify characteristic patterns of tubular damage associated with this disease. Dogs with intrinsic AKI caused by leptospirosis and by other aetiologies were prospectively enrolled. Clinical and clinicopathological variables, including serum and urine chemistry, fractional excretion (FE%) of electrolytes, and urinary neutrophil gelatinase-associated lipocalin (NGAL), were evaluated in both groups and compared statistically. Dogs with leptospirosis (n = 38) had significantly higher serum creatinine concentration than dogs with AKI caused by other aetiologies (n = 37). Serum potassium and glucose concentrations were comparable between groups. Dogs with leptospiral AKI had significantly higher FE of potassium (median 100%, range 20-480 vs. median 68%, range 5-300; P = 0.048), as well as higher magnitude of glucosuria (urine glucose to creatinine ratio, median 0.64, range 0-26 vs. median 0.22, range 0-13; P =  0.023) and frequency of positive glucose dipstick reaction (59% vs. 18%; P =  0.002), than dogs with AKI of other aetiologies. Additional markers of tubular damage considered in this study, including FE of other electrolytes and urinary NGAL, did not differ between groups. In conclusion, when compared to other aetiologies of intrinsic AKI, canine leptospirosis was characterised by increased glucosuria and kaliuresis.

Urinary Fractional Clearance of Sodium in 8 Healthy Beagle Dogs Fed Normal, Low, or Ultralow Sodium Diets

The purpose of this study was to investigate in healthy adult dogs if there was a daily fluctuation in the FC_Na, the role that dietary sodium intake played on the FC_Na, and the role that feeding played on the obtained value for FC_Na. Three different diets were used in a group of 8 healthy beagle dogs in a crossover design. The sodium content of the diets was normal (0.26%), low (0.18%), and ultralow (0.06%). Spot urine and blood samples were collected from which the urine and serum sodium and creatinine concentration were determined, and the FC_Na was calculated. The median FC_Na for the normal, low, and ultralow sodium diets was 0.5, 0.77, and 0.15, respectively. Individual dogs showed a daily variation in FC_Na, and samples which were collected shortly after eating showed the greatest variation. This study showed that in a group of healthy beagle dogs without obvious renal disease, the FC_Na could exceed 1 and that there was both an individual and daily variation in the FC_Na. The greatest variation was seen whilst the dogs were fed the low and ultralow sodium diets and when the samples were collected shortly after eating. This study concluded that an FC_Na > 1% may not be indicative of acute tubular dysfunction in young dogs, and use of the FC_Na for assessing renal function in clinical cases should take into account the animal's diet, as well as the time the samples were taken in relation to feeding.

Urinary neutrophil gelatinase-associated lipocalin as an early biomarker for acute kidney injury in dogs

Neutrophil gelatinase-associated lipocalin (NGAL) is used as an early biomarker of renal injury in people. In dogs, increases in urinary NGAL (uNGAL) precede increases in serum creatinine (sCr) in experimental and clinical evaluations of acute kidney injury (AKI) and chronic kidney disease. This study compared uNGAL in two subsets of dogs with AKI and their respective controls. One set included dogs with snake-envenomation at risk for or presenting with International Renal Interest Society (IRIS) grade I AKI; the other group included dogs with AKI, where renal injury was the result of various causes, and IRIS grade was ≥II. Additionally, this study evaluated haemoglobin (Hb) interference during NGAL analysis in Hb spiked urine and plasma from healthy dogs. In both AKI groups, uNGAL was significantly higher than in matched healthy control dogs (P<0.01). Moreover, uNGAL was significantly higher in dogs with IRIS grade ≥II AKI than in dogs at risk of IRIS grade I AKI (P=0.04). In dogs at risk of IRIS grade I AKI, there were no significant differences in uNGAL and uNGAL/uCr between dogs bitten by cytotoxic or neurotoxic snakes (P=0.44). Additionally, Hb did not interfere with the canine NGAL immunoassay. In conclusion, this study confirms the value of uNGAL as a biomarker for early renal damage: uNGAL was significantly increased in dogs with snake-envenomation at risk for or presenting with IRIS grade I AKI, which could be left undiagnosed if evaluated with the traditional renal biomarker sCr. In addition, Hb did not interfere with NGAL measurement in dogs.

Urine neutrophil gelatinase-associated lipocalin to diagnose and characterize acute kidney injury in dogs

BACKGROUND

Urine neutrophil gelatinase-associated lipocalin (NGAL) is a promising biomarker of acute kidney injury (AKI) in dogs.

OBJECTIVES

To evaluate the utility of urinary NGAL for characterizing AKI according to volume responsiveness, presence of inflammation and sepsis, and prognosis.

ANIMALS

Dogs with AKI (n = 76) and healthy controls (n = 10).

METHODS

Prospective study. Clinical and clinicopathologic data including absolute urine NGAL concentration (uNGAL) and NGAL normalized to urine creatinine concentration (uNGALC) were measured upon admission. Dogs were graded according to International Renal Interest Society (IRIS) AKI guidelines and compared based on AKI features: volume-responsive (VR-) AKI vs. intrinsic (I-) AKI based on IRIS criteria; VR-AKI and I-AKI based on urine chemistry; inflammatory versus noninflammatory; septic versus nonseptic; and survivors versus nonsurvivors. Nonparametric statistics were calculated, and significance set at P < .05.

RESULTS

Urinary NGAL was significantly higher in dogs with AKI compared to controls, regardless of AKI grade. Urinary NGAL did not differ between dogs with VR-AKI and I-AKI based on IRIS criteria, whereas higher uNGALC was recorded in dogs with I-AKI based on urine chemistry. Urinary NGAL was significantly higher in dogs with inflammatory AKI, whereas no difference with respect to sepsis or outcome was identified.

CONCLUSIONS AND CLINICAL IMPORTANCE

Urinary NGAL is a sensitive marker for AKI in dogs, but its specificity is affected by systemic inflammation. Increased urinary NGAL in both I-AKI and VR-AKI also suggests the presence of tubular damage in transient AKI. Combining urine chemistry data with IRIS criteria could facilitate AKI characterization in dogs.

Perioperative urinary heat shock protein 72 as an early marker of acute kidney injury in dogs

OBJECTIVE

Acute kidney injury (AKI) may be a complication in dogs undergoing surgery. Urinary heat shock protein 72 (uHSP72) is a sensitive biomarker of canine AKI. To assess the occurrence of perioperative AKI, based on uHSP72 compared with serum creatinine (sCr), and whether its occurrence is associated with the American Society of Anesthesiology physical status (ASA status).

STUDY DESIGN

Clinical prospective study.

ANIMALS

A total of 80 client-owned and shelter dogs.

METHODS

Dogs scheduled for elective or emergency surgery were assigned ASA status (ASA I-IV). Preoperative and 24 hour postoperative serum and urine samples were collected. sCr, uHSP72 and urinary creatinine (uCr) were measured.

RESULTS

Postoperative uHSP72/uCr concentration [median (range)] of all dogs undergoing surgery [2.40 (0.14-252) ng mg^-1] was significantly increased compared with preoperative uHSP72/uCr [1.30 (0.11-142) ng mg^-1] concentration (p < 0.001). Conversely, postoperative sCr concentration of all dogs [0.88 (0.3-1.6) mg dL^-1] significantly decreased compared with preoperative sCr concentration [0.8 (0.2-5.0) mg dL^-1; p = 0.001]. Median uHSP72/uCr concentration differed both preoperatively (p = 0.007) and postoperatively (p = 0.019) among the ASA status groups. Increased uHSP/uCr was measured in 20 dogs preoperatively and 33 dogs postoperatively, whereas only five dogs fulfilled the criteria of AKI based on sCr.

CONCLUSIONS

The occurrence of increased uHSP72/uCr perioperatively suggests that the proportion of dogs with AKI is considerably higher than perceived.

CLINICAL RELEVANCE

Dogs undergoing surgery should be closely monitored for AKI before and after anesthesia, using currently available markers (e.g., sCr) and more sensitive markers.

Evaluation of urinary γ-glutamyl transferase and serum creatinine in non-azotaemic hospitalised dogs

Urinary and blood biomarkers for diagnosis of acute kidney injury (AKI) in hospitalised dogs were evalueted. This prospective study included 97 dogs, classified according to the International Renal Interest Society classification into no AKI and AKI grade 1 (48-hour increase in serum creatinine≥0.3 mg/dl and/or urinary production <1 ml/kg/hour for at least six hours). A total of 62 of 97 dogs (64 per cent) were classified as AKI 1. A statistically significant difference was found between no AKI and AKI 1 in urine protein to creatinine ratio, urinary γ-glutamyl transferase (uGGT) and uGGT/cu (P<0.0001). Thirteen of 97 dogs (13.4 per cent) that developed increased creatinine and change in AKI grade showed high mortality (n=9/13; 69.2 per cent). The receiver operating characteristic (ROC) curve analysis of uGGT/cu index as a marker for AKI grade 1 had an area under the ROC curve of 0.78; optimal cut-off point was 57.50 u/g, with sensitivity and specificity of 75.4 per cent and 75.6 per cent, respectively. Overall intensive care unit mortality was 23.7 per cent (23/97), 13.4 per cent (13/97) of which died during hospitalisation and 10.3 per cent (10/97) within 28 days after discharge. uGGT is an acceptable marker for distinguishing between AKI 1 and no AKI.

Evaluation of C-reactive protein and its kinetics as a prognostic indicator in canine leptospirosis

OBJECTIVE

To evaluate C-reactive protein at presentation and during hospitalisation in dogs with acute kidney injury resulting from leptospirosis to compare C-reactive protein at presentation in dogs with acute kidney injury of different aetiology and to study its correlation with markers of inflammation, azotaemia and survival.

MATERIALS AND METHODS

Prospective observational study of 41 dogs with acute kidney injury secondary to leptospirosis and 15 control dogs with acute kidney injury of different aetiology. C-reactive protein was measured at presentation in both groups and daily for 7 days in a subgroup of 28 dogs with leptospirosis. The associations of C-reactive protein with neutrophil count, albumin, urea, creatinine and survival were analysed.

RESULTS

C-reactive protein was increased at presentation in all dogs with leptospirosis but was not significantly different from dogs with acute kidney injury of different cause. It was associated with markers of inflammation (neutrophil count, albumin) but not with azotaemia (creatinine, urea). It decreased gradually from presentation to day 4, with significantly lower concentrations in survivors than non-survivors. Initial C-reactive protein was only weakly associated with outcome, but its average concentration from presentation to day 2 was more strongly associated. Absolute and relative changes in C-reactive protein during hospitalisation and creatinine at presentation were not associated with survival.

CLINICAL SIGNIFICANCE

Serial assessment of C-reactive protein may improve outcome prediction in dogs with leptospirosis compared with a single measurement at presentation or with markers of renal function.

Renoprotective effect of oral rehydration solution III in exertional heatstroke rats

AIM

Exertional heastroke (EHS) can lead to acute kidney injury. Oral rehydration solution III (ORS III), recommended by WHO in 2004, is used to rehydrate children with gastroenteritis. This study aimed to characterize the renoprotective effect of ORS III in EHS rats.

METHODS

Rats were randomly divided into Group Control, Group EHS, Group EHS + Water, and Group EHS + ORS. Thirty minutes before the experiment, ORS III was orally administrated to Group EHS + ORS, Water was given to Group EHS + Water. Rats from Group EHS, Group EHS + Water and Group EHS + ORS were then forced to run until they fatigued. Core temperature (Tc) was monitored and 40.5 °C was considered as the onset of heatstroke. Serum creatinine (SCr), blood urea nitrogen (BUN) were measured using an automated biochemical analyzer. Serum neutrophil gelatinase-associated lipocalin (NGAL) was measured using an NGAL ELISA Kit. Light microscopy was used for kidney structural analysis.

RESULTS

SCr level in Group EHS was no different from Group Control (p > .05), while BUN and NGAL levels in Group EHS were higher than Group Control (p <.001, p < .001). SCr, BUN and NGAL concentrations in group EHS + Water were no different from Group EHS (p > .05). SCr, BUN levels in Group EHS + ORS were no different from Group EHS (p > .05). But NGAL levels were significant in these two groups (p = .012). Renal histopathologies of rats in Group EHS and Group EHS + Water showed flattened lumens filled with eosinophilic materials. The damage was milder in Group EHS + ORS, in which injured tubules showed degeneration of the tubular epithelium and sloughing of the brush border membrane.

CONCLUSION

ORS III could alleviate the kidney injury in EHS rats.

Canine environmental hyperthermia: a case series

Cases of hyperthermia caused by exposure to high environmental temperature are not uncommonly encountered in dogs. The circumstances surrounding the exposure to high environmental temperature may be accidental or intentional; thus highlighting the importance to perform a forensic autopsy. This report documents three cases of canine environmentally induced hyperthermia and all dogs in this report died less than 6 hr after exposure to the high environmental temperatures. The most commonly observed macroscopic findings included cutaneous petechial and ecchymotic hemorrhage, pulmonary edema and congestion, and epicardial and endocardial hemorrhage. Microscopically, there was systemic vascular congestion and hemorrhage, fibrin thrombi formation, and occasional enterocyte and/or renal tubular necrosis. The findings from all cases were consistent with hyperthermia induced disseminated intravascular coagulation.

Urinary heat shock protein-72: A novel marker of acute kidney injury and chronic kidney disease in cats

Acute kidney injury (AKI) in cats is associated with high mortality, partially attributed to late recognition of the disease when using currently available markers. Feline chronic kidney disease (CKD) has a variable progression rate. This study aimed to evaluate the sensitivity and specificity of urinary heat shock protein-72 to urinary creatinine ratio (uHSP72:uCr) as a diagnostic and prognostic marker in feline AKI, and as a prognostic indicator in feline CKD. The study included 63 cats, divided into five groups: healthy controls (n=10), urethral obstruction (UO; n=7), CKD (n=15), AKI (16 cats) and acute decompensating CKD (ACKD; n=15). Median uHSP72:uCr (ng/mg) of healthy, UO, CKD, AKI and ACKD cats were 0.44 (range, 0.13-1.1), 1.96 (range, 0.64-11.9), 4.2ng/mg (range, 0.57-22.16), 3.2 (range, 0.42-10.91) and 7.0 (range, 1.2-20.96), respectively, and differed (P<0.001) among groups. uHSP72:uCr was significantly lower in the controls vs. the CKD, AKI and ACKD groups. Receiver operator characteristic analysis of uHSP72:uCr, including the AKI and control groups, showed an area under the curve of 0.93 (95% confidence interval, 0.84-1.00), indicating an excellent predictive performance for diagnosing AKI. A 0.54ng/mg cutoff point corresponded to 94% sensitivity and 70% specificity for diagnosing AKI. The median survival time of cats with CKD with low uHSP72:uCr was longer (P=0.036) than in those with high uHSP72:uCr (561 vs. 112 days, respectively). uHSP72:uCr is a highly sensitive, moderately specific marker of AKI in cats, and is associated with the survival of cats with CKD.

Variability of serum concentrations of cystatin C and urinary retinol-binding protein, neutrophil gelatinase-associated lipocalin, immunoglobulin G, and C-reactive protein in dogs

Background

Markers of kidney dysfunction and damage have potential to detect chronic kidney disease (CKD) in early stages. However, data on long‐term variation of these markers in healthy dogs is lacking and is crucial for the interpretation of results.

Hypothesis/Objectives

To determine temporal variations of serum cystatin C (sCysC) and urinary retinol‐binding protein (uRBP), neutrophil gelatinase‐associated lipocalin (uNGAL), immunoglobulin G (uIgG), and C‐reactive protein (uCRP) in healthy dogs.

Animals

Eight clinically healthy adult Beagles were evaluated.

Methods

Longitudinal observational study. Serum cystatin C was determined by particle‐enhanced nephelometric immunoassay. Urinary retinol‐binding protein, uNGAL, uIgG and uCRP were determined by ELISA and concentrations were indexed to urinary creatinine. Within‐ and between‐dog variance components (VC) and within‐dog coefficients of variation (CV) were determined from blood and urine collected at eight time points over 1.5 years.

Results

Urinary C‐reactive protein (uCRP) concentrations were consistently below the detection limit (5.28 ng/mL). Mean ± within‐dog standard deviation for sCysC, uRBP/c, uNGAL/c and uIgG/c was 0.15 ± 0.01 mg/L, 0.09 ± 0.03 mg/g, 2.32 ± 2.03 μg/g and 12.47 ± 10.98 mg/g, respectively. Within‐dog CV for sCysC, uRBP/c, uNGAL/c and uIgG/c was 8.1%, 33.7%, 87.2% and 88.1%, respectively.

Conclusions and clinical importance

Serum cystatin C, uRBP/c, uNGAL/c and uIgG/c exhibit a wide range of long‐term within‐dog variability. Researchers and veterinarians might need to take this into account when interpreting their results. To assess their diagnostic and predictive ability, future studies need to establish reference ranges for healthy dogs and dogs with CKD.

Fractional excretion of electrolytes in volume-responsive and intrinsic acute kidney injury in dogs: Diagnostic and prognostic implications

Background

The value of fractional excretion (FE) of electrolytes to characterize and prognosticate acute kidney injury (AKI) is poorly documented in dogs.

Objectives

To evaluate the diagnostic and prognostic roles of FE of electrolytes in dogs with AKI.

Animals

Dogs (n = 135) with AKI treated with standard care (February 2014‐December 2016).

Methods

Prospective study. Clinical and laboratory variables including FE of electrolytes, were measured upon admission. Dogs were graded according to the AKI‐IRIS guidelines and grouped according to AKI features (volume‐responsive, VR‐AKI; intrinsic, I‐AKI) and outcome (survivors/non‐survivors). Group comparison and regression analyses with hazard ratios (HR) evaluation for I‐AKI and mortality were performed. P < .05 was considered significant.

Results

Fifty‐two of 135 (39%) dogs had VR‐AKI, 69/135 (51%) I‐AKI and 14/135 (10%) were unclassified. I‐AKI dogs had significantly higher FE of electrolytes, for example, FE of sodium (FENa, %) 2.39 (range 0.04‐75.81) than VR‐AKI ones 0.24 (range 0.01‐2.21; P < .001). Overall, case fatality was 41% (55/135). Increased FE of electrolytes were detected in nonsurvivors, for example, FENa 1.60 (range 0.03‐75.81) compared with survivors 0.60 (range 0.01‐50.45; P = .004). Several risk factors for death were identified, including AKI‐IRIS grade (HR = 1.39, P = .002), FE of electrolytes, for example, FENa (HR = 1.03, P < .001), and urinary output (HR = 5.06, P < .001).

Conclusions and Clinical Importance

Fractional excretion of electrolytes performed well in the early differentiation between VR‐AKI and I‐AKI, were related to outcome, and could be useful tools to manage AKI dogs in clinical practice.

Effects of fenoldopam on kidney function parameters and its therapeutic efficacy in the management of acute kidney injury in dogs with heatstroke

Background

Acute kidney injury (AKI) is common in dogs, but evidence of efficacy of its treatment is lacking.

Objective

To evaluate the efficacy of fenoldopam in the management of AKI.

Animals

Forty dogs with naturally occurring heatstroke.

Methods

Dogs were prospectively enrolled and divided into treatment and the placebo groups (fenoldopam, constant rate infusion [CRI] of 0.1 µg/kg/min or saline, respectively). Urine production (UP) was measured using a closed system. Urinary clearances were performed at 4, 12, and 24 hours after presentation to estimate the effect of fenoldopam on UP, glomerular filtration rate (GFR) and sodium fractional excretion (NaFE).

Results

At presentation, severity of heatstroke, based on a previously developed scoring system, was similar between the study groups, but was significantly worse in nonsurvivors compared with survivors. Fenoldopam administration was not associated with hypotension. Overt AKI was diagnosed, based on the International Renal Interest Society guidelines in 22/40 (55%) of the dogs. Overall, 14/40 dogs (35%) died, with no significant (P = .507) mortality rate difference between the fenoldopam (6/20 dogs; 30%) and placebo (8/20; 40%) groups. The proportion of dogs with AKI did not differ between the fenoldopam and the placebo groups (9/20; 45% versus 13/20; 65%, respectively; P = .204). There were no differences in UP, GFR, and NaFE between the fenoldopam and the placebo groups.

Conclusion and Clinical Importance

Fenoldopam CRI at 0.1 µg/kg/min did not have a clinically relevant effect on kidney function parameters in dogs with severe heatstroke‐associated AKI.

Serum histones as biomarkers of the severity of heatstroke in dogs

Heatstroke is associated with systemic inflammatory response syndrome, leading to multiple organ dysfunction and death. Currently, there is no specific treatment decreasing hyperthermia-induced inflammatory/hemostatic derangements. Emerging studies indicate that histones leaking from damaged cells into the extracellular space are toxic, pro-inflammatory, and pro-thrombotic. We therefore hypothesize that serum histones (sHs) are elevated during heatstroke and are associated with the severity of the disease. Sixteen dogs with heatstroke and seven healthy controls were included in the study. Median serum histones (sHs) upon admission in dogs with heatstroke were significantly higher (P = 0.043) compared to that in seven controls (13.2 vs. 7.3 ng/mL, respectively). sHs level was significantly higher among non-survivors and among dogs with severe hemostatic derangement (P = 0.049, median 21.4 ng/mL vs. median 8.16 ng/mL and P = 0.038, 19.0 vs. 7.0 ng/mL, respectively). There were significant positive correlation between sHs and urea (r = 0.8, P = 0.02); total CO2 (r = 0.661, P = 0.05); CK (r = 0.678, P = 0.04); and prothrombin time (PT) 12 h post presentation (r = 0.888, P = 0.04). The significant positive correlation between sHs and other heatstroke severity biomarkers, and significant increase among severely affected dogs, implies its role in inflammation/oxidation/coagulation during heatstroke. sHs, unlike other prognostic and severity biomarkers in heatstroke, can be pharmacologically manipulated, offering a potential therapeutic target.

Changes in serum proteins in dogs with Ehrlichia canis infection

The aim of this study was the identification of proteins differentially represented in the serum proteome of seropositive dogs with (Group 1) and without (Group 2) clinical-pathologic signs consistent with ehrlichiosis compared to healthy control dogs. Serum samples were collected from 20 dogs of various breeds with naturally occurring ehrlichiosis (10 dogs belonged to Group 1 and 10 to Group 2) and 10 healthy dogs. Two-dimensional electrophoresis (2DE) of pooled serum for each of the group of dogs were run in triplicate. 2D image analysis showed 39 spots differently expressed between Group 1 and Group 2 compared with healthy ones. Mass spectrometry analysis allowed identification of 6 proteins: albumin, haptoglobin (Hp), alpha-1-antitrypsin (AAT), Retinol Binding Protein 4 (RBP-4), alpha-1-acid glycoprotein (AGP) and vitamin D-binding protein (VDBP). When a confirmatory study was performed for albumin, Hp, AAT and RBP-4 by using different assays, significant differences (P < 0.05) between diseased and healthy groups were observed. It can be concluded that there are significant changes in the serum proteome of dogs with ehrlichiosis with modifications in proteins related with the acute phase response such as Hp, albumin and AGP, with vitamin A transport such as RBP-4, with inhibitors of serine proteases and anti-inflammatory proteins such as AAT, and vitamin D metabolism and actin scavengers such as VDBP.

Pathophysiology of heatstroke in dogs - revisited

Heatstroke results from a failure to dissipate accumulated heat during exposure to hot environments, or during strenuous physical exercise under heat stress. It is characterized by core body temperatures > 41°C, with central nervous system dysfunction. Functional morphology and thermoregulatory effectors differences between dogs and humans may require special heatstroke protective adaptations in dogs, however, the risk factors for developing heatstroke are similar in both. In dogs, these include hot, especially highly humid environments, excessive physical activity, obesity, large (>15 kg) body weight, being of certain breed (e.g., Labrador retrievers and brachycephalic breeds), upper airway obstruction and prolonged seizures. Lack of acclimation to heat and physical fitness decreases the survival of heat stroked dogs. At the systemic level, blood pooling within the large internal organs (e.g., spleen, liver) is a major contributor to the development of shock and consequent intestinal ischemia, hypoxia and endothelial hyperpermeability, commonly occurring in heatstroke patients. Evoked serious complications include rhabdomyolysis, acute kidney injury, acute respiratory distress syndrome and ultimately, sepsis and disseminated intravascular coagulation. The most common clinical signs in dogs include acute collapse, tachypnea, spontaneous bleeding, shock signs and mental abnormalities, including depression, disorientation or delirium, seizures, stupor and coma. In such dogs, presence of peripheral blood nucleated red blood cells uniquely occurs, and is a highly sensitive diagnostic and prognostic biomarker. Despite early, appropriate body cooling, and intensive supportive treatment, with no available specific treatment to ameliorate the severe inflammatory and hemostatic derangements, the mortality rate is around 50%, similar to that of human heatstroke victims. This review discusses the pathophysiology of canine heatstroke from a veterinarian's point of view, integrating new and old studies and knowledge.

Urinary heat shock protein 72 as a biomarker of acute kidney injury in dogs

Early recognition of acute kidney injury (AKI) is important, as therapy is potentially more efficacious if instituted early in the course of disease. Urinary heat shock protein-72 to urinary creatinine ratio (uHSP72/uCr) was assessed as a diagnostic and prognostic marker in AKI in dogs. Fifty-three dogs were enrolled in five groups: healthy controls (n=11), urinary tract infection (n=10), chronic kidney disease (CKD; n=11), AKI (n=13), and acute decompensating CKD (n=8). Urinary heat shock protein-72 to urinary creatinine ratio was highest in the AKI group (P<0.001 when compared to the control and urinary tract infection groups, individually; P>0.05 compared to each of the other two groups). The area under the curve (AUC) for the receiver operator characteristic (ROC) analysis of uHSP72/uCr to predict AKI, compared to the control group, was 0.97. A cutoff value of 0.20ng/mg corresponded to sensitivity and specificity of 100% and 82%, respectively. Urinary heat shock protein-72 to urinary creatinine ratio was significantly lower in dogs categorized as survivors vs. non-survivors of AKI; ROC AUC, 0.91 (95% confidence intervals, 0.74-1.0). Urinary heat shock protein-72 to urinary creatinine ratio is a potentially useful diagnostic and prognostic biomarker of AKI in dogs.

Is Progressive Chronic Kidney Disease a Slow Acute Kidney Injury?

International Renal Interest Society chronic kidney disease Stage 1 and acute kidney injury Grade I categorizations of kidney disease are often confused or ignored because patients are nonazotemic and generally asymptomatic. Recent evidence suggests these seemingly disparate conditions may be mechanistically linked and interrelated. Active kidney injury biomarkers have the potential to establish a new understanding for traditional views of chronic kidney disease, including its early identification and possible mediators of its progression, which, if validated, would establish a new and sophisticated paradigm for the understanding and approach to the diagnostic evaluation, and treatment of urinary disease in dogs and cats.