A remnant kidney surgery model in cats induces acute and chronic outcomes that mimic spontaneous chronic kidney disease.

OBJECTIVE: To report acute and chronic outcomes of cats with chronic kidney disease (CKD) induced by a remnant kidney model. ANIMALS: 32 purpose-bred cats (n = 15 female, n = 17 male). PROCEDURES: Cats underwent a 2-stage reduction in renal mass through partial arterial ligation of 1 kidney (day 28) and delayed contralateral nephrectomy (day 0), targeting an 11/12th functional nephrectomy. Acute (days -28 - 29) survival and renal function parameters were compared over time, and the latter were evaluated as predictors for acute mortality. Chronic (days 30 to >1,100) survival, renal function, and morphology were described. RESULTS: Acutely, renal function deteriorated in all cats (mean ± SD baseline and day 28 serum creatinine mean concentration, 1.13 ± 0.23 mg/dL and 3.03 ± 1.20 mg/dL, respectively; P < .001; and GFR, 3.22 mL/min/kg ± 0.12 and 1.21 mL/min/kg ± 0.08, respectively; P < .001). Seven (22%) cats were euthanized after because of clinical signs of uremia after contralateral nephrectomy. Prenephrectomy renal function tests were not significant indicators for survival during this acute phase. Twenty-five cats entered the chronic phase. Ten cats were euthanized at a median of 163 days from nephrectomy because of progressive renal dysfunction. Median survival times were significantly different when stratified by acute kidney injury grade at day 29. Cats in the chronic phase had clinical courses similar to cats with naturally occurring CKD, and most (13/15) were in CKD stage 2. CLINICAL RELEVANCE: The remnant kidney model is effective at reducing kidney function to an extent that mimics important characteristics of spontaneous CKD in cats.

Analysis of genes associated with proinflammatory and profibrotic pathways upregulated in ischemia-induced chronic kidney disease in cats.

OBJECTIVE: To use RNA sequencing (RNAseq) to characterize renal transcriptional activities of genes associated with proinflammatory and profibrotic pathways in ischemia-induced chronic kidney disease (CKD) in cats. SAMPLES: Banked renal tissues from 6 cats with experimentally induced CKD (renal ischemia [RI] group) and 9 healthy cats (control group). PROCEDURES: Transcriptome analysis with RNAseq, followed by gene ontology and cluster analyses, were performed on banked tissue samples of the right kidneys (control kidneys) from cats in the control group and of both kidneys from cats in the RI group, in which unilateral (right) RI had been induced 6 months before the cats were euthanized and the ischemic kidneys (IKs) and contralateral nonischemic kidneys (CNIKs) were harvested. Results for the IKs, CNIKs, and control kidneys were compared to identify potential differentially expressed genes and overrepresented proinflammatory and profibrotic pathways. RESULTS: Genes from the gene ontology pathways of collagen binding (eg, transforming growth factor-ß1), metalloendopeptidase activity (eg, metalloproteinase [MMP]-7, MMP-9, MMP-11, MMP-13, MMP-16, MMP-23B, and MMP-28), chemokine activity, and T-cell migration were overrepresented as upregulated in tissue samples of the IKs versus control kidneys. Genes associated with the extracellular matrix (eg, TIMP-1, fibulin-1, secreted phosphoprotein-1, matrix Gla protein, and connective tissue growth factor) were upregulated in tissue samples from both the IKs and CNIKs, compared with tissues from the control kidneys. CONCLUSIONS AND CLINICAL RELEVANCE: Unilateral ischemic injury differentially altered gene expression in both kidneys, compared with control kidneys. Fibulin-1, secreted phosphoprotein-1, and matrix Gla protein may be candidate biomarkers of active kidney injury in cats.

Diagnosis of Collagen Type III Glomerulopathy Using Picrosirius Red and PASH/Masson's Trichrome Stain.

Canine collagen type III glomerulopathy (Col3GP) is a rare juvenile nephropathy in which irregular type III collagen fibrils and fibronectin accumulate in glomerular capillary walls and the mesangium. Necropsy findings were reviewed from 5 puppies diagnosed with Col3GP at 6 to 18 weeks of age. Histologically, with hematoxylin and eosin stain, the glomerular capillary walls and mesangium were diffusely and globally expanded by homogeneous pale eosinophilic material. Ultrastructurally, the subendothelial zone and mesangium were expanded by fibronectin and cross-banded collagen type III fibrils, diagnostic of Col3GP. Two additional stains were employed to identify the material within glomeruli as fibrillar collagen using light microscopy. In all 5 cases, the material was red with picrosirius red and birefringent under polarized light, and was blue with periodic acid-Schiff/hematoxylin/trichrome (PASH/TRI), thereby identifying it as fibrillar collagen. Based on these unique staining characteristics with picrosirius red and PASH/TRI, Col3GP may be reliably diagnosed with light microscopy alone.

Evaluation of profibrotic gene transcription in renal tissues from cats with naturally occurring chronic kidney disease.

BACKGROUND: Increased gene transcription of hypoxia-induced mediators of fibrosis in renal tissue has been identified in experimentally induced, ischemic chronic kidney disease (CKD). OBJECTIVE: To characterize hypoxia-induced profibrotic pathways in naturally occurring CKD in cats. ANIMALS: Twelve client-owned cats with CKD and 8 healthy control cats. METHODS: In this prospective, cross-sectional study, bilateral renal tissue samples were assessed histologically for inflammation, tubular atrophy, and fibrosis, and by reverse transcription-quantitative PCR for characterization of transcript levels of hypoxia-inducible factor-1α (HIF1A), matrix metalloproteinases-2 (MMP2), -7 (MMP7), and -9 (MMP9), tissue inhibitor of metalloproteinase-1 (TIMP1), transforming growth factor-ß1 (TGFB1), and vascular endothelial growth factor-A (VEGFA). Linear mixed models were used to compare gene transcription between diseased and healthy kidneys, and to examine the association between transcript levels and serum creatinine concentration for all cats, and between transcript levels and histologic scores of diseased kidneys. RESULTS: Kidneys from cats with CKD had significantly higher transcript levels of HIF1A, MMP2, MMP7, MMP9, TIMP1, and TGFB1 (all P < .001), and lower levels of VEGFA (P = .006) than those from control cats. Transcript levels of MMP7 (P = .05) and TIMP1 (P = .005) were positively associated with serum creatinine in cats with CKD, but not in control cats. In diseased kidneys, transcript levels of MMP2 (P = .002), MMP7 (P = .02), and TIMP1 (P = .02) were positively, whereas those of VEGFA (P = .003) were negatively, associated with histologic score severity. CONCLUSION AND CLINICAL SIGNIFICANCE: Evaluation of the expression of the corresponding proteins in larger populations could identify therapeutic targets and/or biomarkers of tubulointerstitial fibrosis in cats.

Profibrotic gene transcription in renal tissues from cats with ischemia-induced chronic kidney disease.

OBJECTIVE: To characterize transcription of profibrotic mediators in renal tissues of cats with ischemia-induced chronic kidney disease (CKD). SAMPLE: Banked renal tissues from 6 cats with experimentally induced CKD (RI group) and 8 healthy control cats. PROCEDURES: For cats of the RI group, both kidneys were harvested 6 months after ischemia was induced for 90 minutes in 1 kidney. For control cats, the right kidney was evaluated. All kidney specimens were histologically examined for fibrosis, inflammation, and tubular atrophy. Renal tissue homogenates underwent reverse transcription quantitative PCR assay evaluation to characterize gene transcription of hypoxia-inducible factor-1α (HIF-1α), matrix metalloproteinase (MMP)-2, MMP-7, MMP-9, tissue inhibitor of metalloproteinase-1 (TIMP-1), transforming growth factor-ß1, and vascular endothelial growth factor A. Gene transcription and histologic lesions were compared among ischemic and contralateral kidneys of the RI group and control kidneys. RESULTS: Ischemic kidneys had greater transcript levels of MMP-7, MMP-9, and transforming growth factor-ß1 relative to control kidneys and of MMP-2 relative to contralateral kidneys. Transcription of TIMP-1 was upregulated and that of vascular endothelial growth factor A was downregulated in ischemic and contralateral kidneys relative to control kidneys. Transcription of HIF-1α did not differ among kidney groups. For ischemic kidneys, there were strong positive correlations between transcription of HIF-1α, MMP-2, MMP-7, and TIMP-1 and severity of fibrosis. CONCLUSIONS AND CLINICAL RELEVANCE: Transcription of genes involved in profibrotic pathways remained altered in both kidneys 6 months after transient renal ischemia. This suggested that a single unilateral renal insult can have lasting effects on both kidneys.

Pancreatic Langerhans cell histiocytosis in a cat.

In contrast to pulmonary Langerhans cell histiocytosis (LCH), which is a proliferative disorder of Langerhans cells that affects the lungs and other organs of cats, LCH involving a single organ system has not been documented in cats, to our knowledge. Herein we describe a case of pancreatic LCH in a 9-y-old castrated male Domestic Shorthaired cat that was evaluated for possible renal transplantation. The cat was hypoglycemic, hyperinsulinemic, and azotemic. Ultrasound examination revealed a diffusely enlarged, normoechoic pancreas. The cat was euthanized because of severe renal azotemia and the possibility of pancreatic neoplasia. Grossly, the pancreas was enlarged, and both kidneys were pale white, firm, and had irregular capsular surfaces. Histologically, the pancreas was expanded with interlobular, intraparenchymal, and ductal clusters of round-to-polygonal cells admixed with fibrous connective tissue and scattered lymphocytes. Infiltrating cells had a moderate amount of eosinophilic cytoplasm, round-to-indented nuclei with finely stippled chromatin and 1 or 2 nucleoli, and were strongly immunoreactive for CD18, ionized calcium-binding adapter molecule 1, and e-cadherin. The morphologic and immunohistochemical features of the pancreatic changes were consistent with single-system LCH.

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

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

Whole genome sequencing confirms source of pathogens associated with bacterial foodborne illness in pets fed raw pet food.

Reports of raw meat pet food containing zoonotic foodborne bacteria, including Salmonella, Escherichia coli, and Listeria monocytogenes, are increasing. Contaminated raw pet food and biological waste from pets consuming those diets may pose a public health risk. The U.S. Food and Drug Administration Veterinary Laboratory Investigation and Response Network conducted 2 case investigations, involving 3 households with animal illnesses, which included medical record review, dietary and environmental exposure interviews, animal sample testing, and whole genome sequencing (WGS) of bacteria isolated from the pets and the raw pet food. For each case investigation, WGS with core genome multi-locus sequence typing analysis showed that the animal clinical isolates were closely related to one or more raw pet food bacterial isolates. WGS and genomic analysis of paired animal clinical and animal food isolates can confirm suspected outbreaks of animal foodborne illness.

Focal Segmental Glomerulosclerosis in Related Miniature Schnauzer Dogs.

Focal segmental glomerulosclerosis (FSGS) recently has been recognized as a common cause of proteinuria in dogs in general, and in Miniature Schnauzer dogs in particular. This study describes the morphologic features present in the kidneys of 8 related proteinuric Miniature Schnauzer dogs. The FSGS, characterized by solidification of portions of the capillary tuft, affected 32% to 49% of examined glomeruli in these dogs. Synechiae, often accompanied by hyalinosis, were present in 13% to 54% of glomeruli and were more prevalent in older dogs. Seven of 8 dogs had arteriolar hyalinosis. Ultrastructurally, all dogs had evidence of a podocytopathy in the absence of electron-dense deposits, glomerular basement membrane splitting, or fibrils. All dogs had multifocal to extensive podocyte foot process effacement. Other podocyte changes included microvillous transformation, the presence of vacuoles or protein resorption droplets, cytoplasmic electron-dense aggregates, and occasional binucleation. Variable amounts of intraglomerular lipid were present in all dogs. All dogs were proteinuric, with measured values for the urine protein-to-creatinine ratio ranging from 1.2 to 6.5. Azotemia was mild to absent and dogs were euthanatized at 5.1 to 14 years of age, in all cases due to nonrenal diseases. The underlying cause of FSGS in these Miniature Schnauzer dogs has yet to be determined, but contributors likely include genetic podocytopathy, lipid abnormalities, and glomerular hypertension.

Glomerular Lipidosis in Dogs.

Glomerular lipidosis (GL) is characterized by dilated glomerular capillary loops containing lipid-laden cells (foam cells). Previously, GL was considered to be an incidental finding because affected dogs were typically not azotemic. However, the International Renal Interest Society staging system for canine chronic kidney disease has increased the awareness of other clinical parameters (eg, proteinuria and hypertension) that should be included in the assessment of renal function. As such, the aim of this study was to determine clinical abnormalities and concurrent renal lesions in dogs with GL. GL was identified in renal biopsies from 46 dogs evaluated by the International Veterinary Renal Pathology Service. GL was the sole diagnosis in 5 of 46 cases (11%), all of which were proteinuric. All 5 dogs had at least 1 additional clinicopathologic abnormality consistent with renal disease, including hypertension (4), azotemia (3), and/or hypoalbuminemia (2). The remaining 41 dogs had GL in combination with other glomerular lesions, the most common being focal segmental glomerulosclerosis (16, 35%), lesions consistent with juvenile nephropathy (8, 17%), and glomerular amyloidosis (5, 11%). Overall, dogs with severe GL were younger than were those with mild GL ( P < .001). The percentage of glomeruli affected by GL differed by concurrent diagnoses ( P = .034), with the highest percentage of affected glomeruli in dogs with GL alone or those with concurrent juvenile nephropathy. These findings suggest that GL should be a recognized histologic phenotype of glomerular injury associated with clinical renal dysfunction and/or juvenile nephropathies.

Atypical cytologic presentation of a histiocytic sarcoma in a Cavalier King Charles Spaniel dog.

A Cavalier King Charles Spaniel dog was presented because of a 10-d history of progressive vomiting, inappetence, and lethargy, with mild neurologic signs. Fine-needle aspirates of splenic nodules seen on ultrasound were suggestive of a carcinoma. On autopsy, a disseminated neoplasm was present in the lung, spleen, and adrenal glands. Additionally, there was a Chiari-like malformation of the skull with corresponding syringomyelia of the cranial spinal cord. Histologically, the neoplasm was comprised of a pleomorphic population of round cells with a high mitotic rate. Cells stained positive for vimentin and CD18 and negative for cytokeratin, chromogranin A, CD3, CD20, MHC II, and CD11d, and hence the tumor was diagnosed as a histiocytic sarcoma. The cytologic presentation in this case is uncommon for this type of tumor, as was the clinical presentation.

Assessment of Acute Kidney Injury and Renal Fibrosis after Renal Ischemia Protocols in Cats.

In an attempt to identify a feline model of acute or chronic kidney disease, this study was designed to evaluate the effects of 15 or 30 min of bilateral renal ischemia (RI) and 60 min of unilateral RI with delayed contralateral nephrectomy as models of acute kidney injury and chronic interstitial fibrosis in cats. Adult, purpose-bred, USDA Class A cats (n = 14) were randomly assigned to receive bilateral RI for 15 min (n = 3) or 30 min (n = 3), unilateral RI for 60 min with a delayed (2 wk) contralateral nephrectomy (n = 5), or sham unilateral RI with a delayed contralateral nephrectomy (n = 3). Serum creatinine concentration, urine specific gravity, and plasma clearance of iohexol were assessed at several time points throughout the study. Renal interstitial inflammatory cell counts and descriptive histopathology were acquired in all cats. Histomorphometry was used to quantify renal interstitial fibrosis and collagen at 120 d after RI in cats undergoing unilateral RI. Renal histopathology was evaluated at 21 and 120 d after bilateral and unilateral RI, respectively. Neither duration of bilateral RI resulted in appreciable histologic renal damage at 21 d after ischemia. At 120 d after ischemia, variable amounts of renal fibrosis were noted after 60 min of unilateral RI with delayed contralateral nephrectomy. Neither of the tested methods is a suitable model of consistent renal interstitial fibrosis in cats. Healthy cats appear able to sustain bilateral RI for as long as 30 min with no apparent effects on renal morphology or function at 21 d after ischemia.

Efficacy of allogeneic mesenchymal stem cell administration in a model of acute ischemic kidney injury in cats.

OBJECTIVE: To evaluate the effects of allogeneic mesenchymal stem cells (MSCs) in a model of ischemic acute kidney injury (AKI). STUDY DESIGN: Randomized controlled trial. ANIMALS: Adult, purpose-bred research cats (n=15) and a historical reference group (n=3). METHODS: Cats underwent unilateral, in vivo, warm renal ischemia, then intravenous administration of 4 million adipose-derived MSCs, bone marrow-derived MSCs, or fibroblasts (n=5/treatment) 1h after reperfusion. Serum creatinine and blood urea nitrogen concentrations were measured at baseline and days 1 and 6. Urine specific gravity, urine protein to urine creatinine ratio, and glomerular filtration rate were measured at baseline and day 6. Both kidneys were harvested on day 6; histopathology was described and scored and smooth muscle actin was quantified with histomorphometry. A 2-way ANOVA was used to compare time and treatment. Chi square analysis was used to determine the % of cats with at least International Renal Interest Society (IRIS) Grade 1 AKI. RESULTS: Time, but not treatment, had a significant effect on renal function. No difference was noted in % of cats with IRIS AKI. Significantly fewer mitotic figures were observed in ischemic kidneys that received bone-marrow derived MSCs vs. fibroblasts. No differences in smooth muscle actin staining were noted. CONCLUSIONS: This study did not support the use of allogeneic MSCs in AKI in the regimen described here. Type of renal injury, MSC dose, allogenicity, duration, and route or timing of administration could influence the efficacy MSCs.

Proliferative, necrotizing and crescentic immune complex-mediated glomerulonephritis in a cat.

CASE SUMMARY: A 5-year-old cat was examined for vomiting and anorexia of 2 days' duration. Azotemia, hyperphosphatemia and hypoalbuminemia were the main biochemical findings. Serial analyses of the urine revealed isosthenuria, proteinuria and eventual glucosuria. Hyperechoic perirenal fat was detected surrounding the right kidney by ultrasonography. Histopathologic evaluation of ante-mortem ultrasound-guided needle biopsies of the right kidney was consistent with proliferative, necrotizing and crescentic glomerulonephritis with fibrin thrombi, proteinaceous and red blood cell casts, and moderate multifocal chronic-active interstitial nephritis. Owing to a lack of clinical improvement, the cat was eventually euthanized. Post-mortem renal biopsies were processed for light microscopy, transmission electron microscopy and immunofluorescence. This revealed severe focal proliferative and necrotizing glomerulonephritis with cellular crescent formation, podocyte injury and secondary segmental sclerosis. Ultrastructural analysis revealed scattered electron-dense deposits in the mesangium, and immunofluorescence demonstrated positive granular staining for λ light chains, consistent with immune complex-mediated glomerulonephritis. Severe diffuse acute tubular epithelial injury and numerous red blood cell casts were also seen. RELEVANCE AND NOVEL INFORMATION: To our knowledge, this is the first report of naturally occurring proliferative, necrotizing and crescentic immune complex glomerulonephritis in a cat.

Diagnostic features in 10 naturally occurring cases of acute fatal canine leptospirosis.

The current report describes the diagnostic features in 10 cases of acute fatal canine leptospirosis with minimal renal and hepatic changes that may present a diagnostic challenge for the pathologist. Most affected dogs were less than 6 months of age and had a biochemical profile consistent with hepatorenal dysfunction. Clinical signs consisted of vomiting, depression, icterus, dehydration, diarrhea, and anorexia. All dogs died or were humanely euthanized within 3-7 days after the onset of clinical disease. Necropsy findings included pulmonary edema with hemorrhages, icterus, renal and hepatic pallor and swelling, and gastric edema with hemorrhage. Despite severe azotemia, histological changes in the kidneys were subtle in all dogs, and included mild renal tubular simplification, with single-cell necrosis and attenuation, along with minimal interstitial lymphoplasmacytic inflammation, edema, and hemorrhage. Hepatic lesions included scattered hepatocellular single-cell necrosis and hepatocellular dissociation. Prominent extrarenal lesions typically associated with uremia including vascular fibrinoid necrosis in multiple organs, pulmonary mineralization with occasional fibrinosuppurative exudation, and gastric mineralization were also present. Postmortem diagnostic confirmation was based on the detection of leptospiral antigen on fresh renal samples by fluorescent antibody test and on the demonstration of intact spirochetes in sections of kidneys using immunohistochemical staining. Acute fatal canine leptospirosis occurred as a fulminant hepatorenal disease affecting mainly young dogs, and the diagnosis was dependent on the recognition of the subtle renal changes with confirmation via fluorescent antibody testing or immunohistochemical staining.

Evaluation of glomerular filtration rate in cats with reduced renal mass and administered meloxicam and acetylsalicylic acid.

OBJECTIVE: To determine whether administration of meloxicam or acetylsalicylic acid alters glomerular filtration rate (GFR) in cats with renal azotemia. ANIMALS: 6 young adult cats. PROCEDURES: 3 sexually intact male cats and 3 sexually intact female cats had surgically reduced renal mass and azotemia comparable to International Renal Interest Society chronic kidney disease stages 2 and 3. Renal function was evaluated by measurement of serum creatinine concentration, urinary clearance of exogenously administered creatinine, and the urine protein-to-creatinine concentration ratio (UP:C). Measurements taken in cats receiving placebo at the beginning and end of the study were compared with results obtained at the end of 7 days of treatment with either meloxicam (0.2 mg/kg, SC, on day 1; 0.1 mg/kg, SC, on days 2 to 7) or acetylsalicylic acid (20 mg/kg, PO, on days 1, 4, and 7). RESULTS: No significant treatment effects on urinary clearance of exogenously administered creatinine, serum creatinine concentration, or UP:C were detected. Mean ± SEM serum creatinine concentration and urinary clearance of exogenously administered creatinine measurements following 7 days of treatment with meloxicam (serum creatinine concentration, 2.67 ± 0.17 mg/dL; urinary clearance of exogenously administered creatinine, 1.34 ± 0.08 mL/min/kg) and acetylsalicylic acid (serum creatinine concentration, 2.62 ± 0.12 mg/dL; urinary clearance of exogenously administered creatinine, 1.35 ± 0.07 mL/min/kg) were not significantly different from the mean baseline values for these variables (serum creatinine concentration, 2.77 ± 0.14 mg/dL; urinary clearance of exogenously administered creatinine, 1.36 ± 0.07 mL/min/kg). CONCLUSIONS AND CLINICAL RELEVANCE: Neither meloxicam nor acetylsalicylic acid had a measurable effect on urinary clearance of exogenously administered creatinine, serum creatinine concentration, or UP:C. These results are consistent with the hypothesis that GFR of euvolemic cats with normal or reduced renal function is not dependent on cyclooxygenase function.

Lymphosarcoma associated with Heterobilharzia americana infection in a dog.

Hepatic T-cell lymphosarcoma with involvement of regional lymph nodes and concurrent schistosomiasis were diagnosed in an 11-year-old male neutered mixed-breed dog with a history of chronic weight loss, inappetence, vomiting, and diarrhea. Trematode ova present in the hepatic parenchyma and mesenteric node were surrounded by sheets of neoplastic lymphocytes while those in the intestinal wall were surrounded by large numbers of non-neoplastic lymphocytes. Immunohistochemistry revealed that both the neoplastic and hyperplastic populations were T lymphocytes. The ova were identified by fecal saline sedimentation as Heterobilharzia spp., and fecal ova shedding resolved after praziquantel anthelmintic treatment. The lymphoma progressed despite chemotherapy, and the dog was euthanized after developing neurologic signs and a necropsy was performed. A monomorphic population of neoplastic T cells expanded and replaced normal architecture in the liver and spleen, surrounded nerve roots within the cauda equina, and infiltrated the meninges of the brain. The presence of schistosome ova embedded within neoplastic T-cell infiltrates suggests that, as previously reported in human schistosomiasis, heterobilharziasis may be associated with neoplasia.