Evaluation of Kidney Injury in Dogs with Pyometra Based on Proteinuria, Renal Histomorphology, and Urinary Biomarkers

摘要

AbstractBackground: Proteinuria is a feature of pyometra-associated renal dysfunction, but its prevalence and clinical relevance are not well characterized.Objectives: To define which subset of dogs with pyometra has clinically relevant kidney injury by quantification of proteinuria; light, immunofluorescence, and electron microscopic examination of kidney biopsy specimens; and measurement of urinary biomarkers.Animals: Forty-seven dogs with pyometra. Ten clinically healthy intact bitches of comparable age.Methods: Prospective study. Routine clinicopathological variables including urinary protein to creatinine ratio (UPC) were analyzed. Validated assays were used to quantify urinary biomarkers for glomerular (urinary albumin, urinary immunoglobulin G, urinary C-reactive protein, urinary thromboxane B₂) and tubular function (urinary retinol-binding protein, urinary N-acetyl-β-d-glucosaminidase). Kidney biopsy specimens from 10 dogs with pyometra and dipstick urine protein concentrations of 2+ or 3+ were collected during ovariohysterectomy. Urinalysis was repeated within 3 weeks after surgery in 9 of the 10 dogs.Results: UPC (median, range) was significantly higher in dogs with pyometra (0.48, 0.05–8.69) compared with healthy bitches (0.08, 0.02–0.16) (P .01). Twenty-two of 47 dogs with pyometra had UPC0.5, 12 had UPC1.0, and 7 had UPC2.0. Glomerulosclerosis and tubulointerstitial nephritis were common kidney biopsy findings in proteinuric dogs with pyometra. Dogs with glomerulosclerosis (5/10), either global or focal and segmental, had UPC1.0 at ovariohysterectomy and afterward. Dogs with structural glomerular and tubular changes mostly had urinary biomarker to creatinine ratios above the 75th percentile.Conclusion: Dogs with pyometra and UPC1.0 or high ratios of urinary biomarkers appear likely to have clinically relevant renal histologic lesions and require monitoring after ovariohysterectomy. Future studies should evaluate the role of pyometra-associated pathogenic mechanisms in causing or exacerbating focal and segmental glomerulosclerosis in dogs.