# Organ-Sparing Surgical Management of a Uriniferous Perinephric Pseudocyst Associated with a Calyceal Diverticulum in a Cat with a Solitary Kidney

## TL;DR

A cat with one kidney had a urine-filled cyst around its kidney, which was successfully treated with a kidney-preserving surgery instead of removing the kidney.

## Contribution

This is the first report of an organ-sparing surgical approach for feline uriniferous perinephric pseudocysts.

## Key findings

- Computed tomography identified the exact urinary leakage pathway from a calyceal diverticulum to the subcapsular space.
- An omental patch successfully sealed the defect, preserving kidney function and preventing recurrence.
- The cat's renal function normalized and remained stable for over a year post-surgery.

## Abstract

Perinephric pseudocysts are fluid-filled spaces that develop around the kidneys. In rare cases, these cysts contain urine due to urinary leakage, and nephrectomy is typically required to prevent ongoing extravasation. However, this approach is not feasible in cats with a single kidney. We report the case of a congenitally single-kidney cat that developed a urine-filled perinephric pseudocyst secondary to abnormal leakage from a small renal outpouching. Advanced computed tomography imaging clearly demonstrated urinary leakage. Rather than performing a nephrectomy, the defect was sealed using an omental patch. The fluid resolved quickly, renal function recovered, and no recurrence was observed. This case demonstrates that careful imaging and kidney-preserving surgery can be successful alternatives for selected cases.

Uriniferous perinephric pseudocysts (PNPs) are a rare condition in cats, primarily managed by nephrectomy to eliminate persistent urinary leakage. Organ preservation is critical in cases with solitary kidneys. This report describes a cat with congenital absence of the right kidney that developed a uriniferous PNP secondary to abnormal communication between the calyceal diverticulum and subcapsular space. A 6-year-and-11-month-old neutered male Ragdoll cat presented with abdominal distension and lethargy. Ultrasonography revealed an extensive subcapsular perinephric fluid and a cystic lesion adjacent to the renal pelvis. Contrast-enhanced computed tomography with excretory urography directly demonstrated the time-dependent passage of contrast medium from the renal pelvis into the calyceal diverticulum and subsequent leakage into the subcapsular space, allowing precise identification of the renal leakage pathway. Based on these findings, an operation was performed using a non-vascularized free omental plug inserted into the diverticular opening and secured using capsular sutures. Postoperative drainage resolved rapidly, renal function normalized, and no recurrence was detected during long-term follow-up of up to 465 days. To the best of our knowledge, this is the first report to describe an organ-sparing surgical approach that directly addresses the renal leakage pathway in feline uriniferous PNPs.