Evaluation of kidney injury in dogs with pyometra based on proteinuria, renal histomorphology, and urinary biomarkers

J Vet Intern Med. 2011 Sep-Oct;25(5):1075-83. doi: 10.1111/j.1939-1676.2011.0772.x. Epub 2011 Aug 16.

Abstract

Background: 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 B(2)) 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 UPC>0.5, 12 had UPC>1.0, and 7 had UPC>2.0. 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 UPC>1.0 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 UPC>1.0 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acute Kidney Injury / diagnosis
  • Acute Kidney Injury / etiology
  • Acute Kidney Injury / pathology
  • Acute Kidney Injury / urine
  • Acute Kidney Injury / veterinary*
  • Animals
  • Biomarkers / urine
  • Creatinine / urine
  • Dog Diseases / diagnosis*
  • Dog Diseases / pathology
  • Dog Diseases / urine
  • Dogs
  • Female
  • Kidney / pathology*
  • Kidney / ultrastructure
  • Microscopy, Electron, Transmission / veterinary
  • Microscopy, Fluorescence / veterinary
  • Prospective Studies
  • Proteinuria / diagnosis
  • Proteinuria / urine
  • Proteinuria / veterinary
  • Pyometra / complications
  • Pyometra / pathology
  • Pyometra / veterinary*

Substances

  • Biomarkers
  • Creatinine