European Veterinary Renal Pathology Service: A Survey Over a 7-Year Period (2008-2015)

Weekly Biological Variation of Urine Protein Creatinine Ratio and Urine Specific Gravity in Healthy Dogs

BACKGROUND

Urine protein-creatinine ratio (UPC) and urine specific gravity (USG) are important measurements in the determination of renal proteinuria and chronic kidney disease. Biological and analytical variation estimates of these analytes to calculate the index of individuality (IoI) and a reference change value (RCV) are important to determine whether a population-based reference interval can be used to detect clinically meaningful changes and facilitate the interpretation of serial measurements.

OBJECTIVE

Determine the biological variation of UPC and USG using calculations of RCV and IoI in healthy dogs.

ANIMALS

Eleven healthy client-owned young adult dogs.

METHODS

Prospective observational study. First-morning urine samples were collected by voiding once weekly for 6 consecutive weeks for batch analysis. Twenty random samples were run in duplicate. Urine protein concentration, urine creatinine concentration, and USG were measured using a colorimetric pyrogallol red molybdate complex, enzymatic Jaffe method, and manual refractometer, respectively. Restricted maximum likelihood estimations were used to determine within-individual, between-individual, and analytical coefficients of variation and calculation of RCV and IoI.

RESULTS

All dogs were non-proteinuric at enrollment (UPC < 0.2) and remained non-proteinuric on subsequent measurements. Urine protein concentration, urine creatinine concentration, UPC, and USG had intermediate individuality. The RCV was 73% for urine protein concentration, 68% for urine creatinine concentration, 31% for UPC, and 3% for USG.

CONCLUSION

Population-based reference intervals for UPC and USG should be interpreted cautiously for single measurements and calculated RCVs should be applied to serial measurements to identify clinically meaningful changes.

Severe glomerular fibrin thrombosis in a dog

Here, we present a case of severe glomerular fibrin thrombosis in a dog with lymphoma. A 3-year-old neutered male Chihuahua presented with acute kidney injury, hypoalbuminemia, and transudate ascites. The dog showed symmetric enlargement of the spleen, which was diagnosed as B-cell lymphoma based on cytology and polymerase chain reaction tests. The dog died after intensive care, and the kidneys were removed for histopathological examination. Light microscopy, immunofluorescence, and electron microscopy analyses were performed for renal pathology; however, the findings did not support the evidence of protein-losing nephropathy. Instead, the endocapillary accumulation of fibrin thrombi was prominent in most glomeruli. A diagnosis of severe glomerular fibrin thrombosis was established, and hypoalbuminemia was considered the underlying cause of kidney damage.

Nephrology in Veterinary Medicine

Veterinary nephrology is a specialized field of veterinary medicine providing a high level of care for animals with all types of kidney disease. Veterinarians complete extensive training to become board-certified in veterinary nephrology-urology. Companion animal nephrology is the most advanced field; however, all species are afflicted by a variety of renal disorders. Most naturally occurring animal kidney diseases have similar disorders found in people; where veterinary research is lacking, clinical management is often modified from standard of care in people. Veterinarians have become adept at scaling down procedures to safely perform them on dogs and cats weighing only a few kilograms. Advanced diagnostics (renal biopsy, cystoscopy, fluoroscopic studies, etc. ) and therapeutics (renal replacement therapy, interventional endourology, etc. ) are commonly performed within the practice of veterinary nephrology-urology. Collaboration between veterinary and human nephrologists may advance both disciplines and improve care for people and animals alike.

Mycophenolate mofetil and telmisartan for the treatment of proteinuria secondary to minimal change disease podocytopathy in a dog

A 3-year-old entire female Springer Spaniel, with a previous diagnosis of meningoencephalitis of unknown origin diagnosed 2 years before presentation and treated with long term administration of prednisolone, developed proteinuria. Laboratory findings revealed hypoalbuminemia, hypercholesterolemia, and proteinuria. Further investigations excluded underlying causes. Renal biopsies were performed. The glomeruli and the tubulointerstitial compartment did not show any anomalies on light microscopy and immunofluorescence staining did not reveal abnormalities. Transmission electron microscopy revealed moderate podocyte injury consisting of foot process effacement and microvillus transformation of the cytoplasm. The dog was diagnosed with primary minimal change disease of the podocytes and treated with telmisartan and mycophenolate mofetil. Abnormalities of serum albumin, cholesterol, and proteinuria resolved within 4 weeks. Minimal change disease has been reported in dogs, but this is a case report of proteinuria secondary to minimal change disease successfully treated with mycophenolate mofetil and telmisartan.

Association of ultrasonographic features with histologic findings in 71 dogs with protein-losing nephropathy (2008-2018)

OBJECTIVE

To determine whether ultrasonographic features in dogs with protein-losing nephropathy (PLN) were associated with renal biopsy findings and compare corticomedullary ratios between dogs with PLN versus non-renal disease.

ANIMALS

71 dogs with PLN and 33 dogs without renal disease.

PROCEDURES

Medical records and archived ultrasonographic images for dogs with PLN that underwent renal biopsy between 2008 and 2018 were reviewed. Corticomedullary ratios were measured.

RESULTS

In dogs with PLN, median serum creatinine and BUN concentrations and urine-protein-to-creatinine-ratio prior to renal biopsy were 3.4 mg/dL (interquartile range [IQR], 1.2 to 5.3 mg/dL), 80 mg/dL (IQR, 28 to 105 mg/dL), and 11.4 (IQR, 6.4 to 18.3), respectively. Histologic abnormalities within the tubulointerstitial space were associated with cortical echogenicity. Gastric wall thickness > 5 mm was associated with a histologic diagnosis of acute glomerular disease. Dogs with immune complex-mediated glomerular disease were more likely to have abnormal gastric mural architecture. Other ultrasonographic features of the kidneys, liver, and stomach and the presence of ascites did not help to differentiate immune complex-mediated from non-immune complex-mediated glomerular disease, acute from chronic disease, or amyloid from non-amyloid disease or distinguish whether tubulointerstitial disease was present or absent. Median left corticomedullary ratio for 66 dogs with PLN (1.2) was significantly higher than that for the 33 dogs without renal disease (1.0).

Clinical Relevance

Ultrasonographic features were poorly associated with specific pathological disorders in dogs with PLN. In this study, the corticomedullary ratio was higher in dogs with PLN, indicating the presence of cortical thickening, but the clinical relevance is unknown.

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

BACKGROUND

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

OBJECTIVE

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

ANIMALS

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

METHODS

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

RESULTS

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

CONCLUSIONS AND CLINICAL IMPORTANCE

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

Evaluation of acute kidney injury in dogs with complicated or uncomplicated Babesia rossi infection

Dogs with babesiosis can present with multiple complications, including acute kidney injury (AKI). The objective of this study was to characterize AKI in dogs with babesiosis caused by Babesia rossi at presentation and after treatment. Thirty-five client-owned dogs with B. rossi infection and 10 control dogs were included in this prospective observational study. Blood and urine were collected in Babesia-infected dogs at presentation (T₀, n = 35), after 24 h (T_24h, n = 11), and after 1 month (T_1m, n = 9). The following urinary kidney injury biomarkers were assessed: urinary protein to creatinine ratio (UPC), urinary glomerular injury biomarkers (immunoglobulin G (uIgG) and C-reactive protein (uCRP)), and urinary tubular injury biomarkers (retinol-binding protein (uRBP) and neutrophil gelatinase-associated lipocalin (uNGAL)). Serum functional renal biomarkers were creatinine (sCr) and symmetric dimethylarginine (sSDMA). Post-mortem kidney biopsies were analyzed by light and transmission electron microscopy. At T₀, all kidney injury biomarkers were significantly higher in Babesia-infected dogs compared to healthy controls (P < 0.001), while functional renal biomarkers were not significantly different (P > 0.05). At T_24h, all urinary tubular injury biomarkers and UPC decreased significantly (P < 0.01), while glomerular injury biomarkers did not (P = 0.084). At T_1m, all urinary kidney injury biomarkers decreased to values not significantly different from healthy controls (P > 0.5). Significant changes in functional renal biomarkers were not seen after treatment (P > 0.05). Dogs with complicated babesiosis had significantly higher glomerular injury biomarkers, UPC, and sSDMA compared to uncomplicated cases (P < 0.05), while all tubular injury biomarkers and sCr were not significantly different (P > 0.1). Dogs with babesiosis caused by B. rossi showed transient kidney injury, which was detected by all kidney injury biomarkers, but remained undetected by functional biomarkers. All infected dogs, irrespective of disease severity, suffered comparable kidney injury based on tubular injury biomarker concentrations, while loss of function was seen more often in dogs with complicated babesiosis based on sSDMA results.

Occurrence, management and outcome of immune-complex glomerulonephritis in dogs with suspected glomerulopathy in the UK

OBJECTIVES

To determine the proportion of dogs diagnosed with immune-complex glomerulonephritis in a large cohort of UK dogs with clinical suspicion of glomerular disease in which renal histopathology, including routine light microscopy, transmission electron microscopy and immunofluorescence, had been performed. The second objective was to describe treatment and long-term clinical outcome of dogs diagnosed with immune-complex glomerulonephritis.

MATERIALS AND METHODS

Sixty-two UK dogs that underwent renal biopsies for investigation of suspected glomerulopathy (urine protein-to-creatinine ratio persistently >0.5) were included in this retrospective multicentre study. Signalment, clinico-pathological abnormalities, histopathological diagnosis, treatment following diagnosis and survival were recorded.

RESULTS

Seventeen (27%) of the dogs with suspected glomerular disease were diagnosed with immune-complex glomerulonephritis and nine (53%) of these were still alive at the study end point, with a median follow-up of 366 days (range 52 to 1299). Six dogs diagnosed with immune-complex glomerulonephritis were treated with mycophenolate. Four received mycophenolate alone for immunosuppression and two received mycophenolate and chlorambucil; all these six dogs were alive at data collection [median follow-up time 712.5 days (range 73 to 1299)]. Seven dogs diagnosed with immune-complex glomerulonephritis did not receive immunosuppressive treatment; only one of these dogs was alive at study end point [median survival time 302 days (range 52 to 723)].

CLINICAL SIGNIFICANCE

Immune-complex glomerulonephritis may be less common in the UK than previously reported in North America and mainland Europe, reducing the likelihood of treatment modification following renal biopsy. Mycophenolate was the most commonly used immunosuppressant for cases of immune-complex glomerulonephritis.

Immune-complex glomerulonephritis in cats: a retrospective study based on clinico-pathological data, histopathology and ultrastructural features

BACKGROUND

Chronic kidney disease (CKD) has typically a non-immune mediated origin in cats and immune-complex glomerulonephritis (ICGN) is scarcely described. Aims of this study were to characterize ICGN by light and electron microscopy and identify associations with clinico-pathological findings. In addition, comparisons between cats with ICGN and non immune-complex glomerulonephritis (non-ICGN) were performed. Renal samples examined between 2010 and 2019 were considered if both light and electron microscopy were performed. Signalment, feline immunodeficiency virus (FIV) and leukemia virus (FeLV) status, serum creatinine concentration, urine protein-to-creatinine (UPC) ratio, systolic blood pressure (SBP) and International Renal Interest Society (IRIS) stage were retrieved and used for comparisons.

RESULTS

Sixty-eight client-owned cats were included. Thirty-seven cats (54.4%) had ICGN and 31 (45.6%) non-ICGN. Eighteen (48.6%) with ICGN had membranous glomerulonephropathy (MGN), 14 (37.8%) membranoproliferative glomerulonephritis (MPGN), and 5 (13.5%) mesangioproliferative glomerulonephritis (MeGN). Clinico-pathological data were not associated with any type of ICGN. Among cats with non-ICGN, 11 (35.5%) had end-stage CKD, 9 (29%) focal segmental glomerulosclerosis, 6 (19.4%) global and multifocal mesangiosclerosis, 2 (6.5%) glomerular atrophy, 2 (6.5%) renal dysplasia and 1 (3.1%) amyloidosis. Eight (25.8%) cats with non-ICGN had chronic interstitial nephritis (CIN) grade 1, 13 (41.9%) grade 2 and 10 (32.3%) grade 3; creatinine and UPC ratio increased with CIN grades (p = 0.001, p < 0.001). Cats with ICGN were more frequently FIV or FeLV-infected (OR:11.4; 95%CI:1.4-94.4; p = 0.024), had higher UPC ratio (OR:6.8; 95%CI:2.5-18.2; p < 0.001) and were younger (OR:0.9; 95%CI:0.7-1.0; p = 0.042) than cats with non-ICGN.

CONCLUSIONS

MGN and MPGN were the most common morphological diagnoses of ICGN in cats. Unfortunately, none of the investigated findings differentiated ICGN morphological diagnoses. Serum creatinine concentration and UPC ratio were directly associated with grades of CIN (p = 0.001 and p < 0.001, respectively), confirming previous literature. More ICGN than non-ICGN was observed in cats with retroviral infections, younger cats and higher UPC ratio.