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

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.