Retroperitoneal fibrosis in feline renal transplant recipients: 29 cases (1998-2011).

Objective: To evaluate features, treatment, and prognosis associated with retroperitoneal fibrosis that developed after renal transplantation in cats.

Design: Retrospective case series.

Animals: 29 cats.

Procedures: Medical records of cats that developed retroperitoneal fibrosis after renal transplantation at the College of Veterinary Medicine, University of Pennsylvania, between 1998 and 2011 were reviewed for signalment, date of transplantation, age, results of urine and blood analyses, blood pressure at the time of diagnosis, infectious disease and medication anamneses, anesthetic protocols, and intraoperative complications.

Results: Of 138 transplant recipients, 29 (21%) developed clinically important retroperitoneal fibrosis. Nineteen (66%) were male, and median age at the time of renal transplantation was 8 years (range, 4 to 13 years). Median number of days after transplantation to diagnosis of retroperitoneal fibrosis was 62 (range, 4 to 730 days; mean, 125 days). The most common clinical signs were lethargy and anorexia. All affected cats were azotemic (BUN concentration > 32 mg/dL; creatinine concentration > 2.0 mg/dL) and anemic (PCV < 35%) at the time of retroperitoneal fibrosis diagnosis, although cats were nonazotemic at the time of discharge following transplantation, and anemia was less pronounced. Twenty-five cats successfully underwent surgical ureterolysis in which scar tissue was dissected away from the allograft ureter to relieve extraluminal compression. Retroperitoneal fibrosis recurred in 6 (22%) cats a median of 180 days (range, 8 to 343 days) following the original diagnosis and was treated successfully by repeated ureterolysis.

Conclusions And Clinical Relevance: Retroperitoneal fibrosis occurred in a substantial percentage of feline renal transplant recipients and should be considered a differential diagnosis in any feline renal transplant recipient with clinicopathologic findings, imaging abnormalities, or signs suggestive of obstructive uropathy.