Unilateral concurrence of pyelocaliceal diverticula and intracapsular angiomyolipoma in the kidney of a cat.

A 7-month-old cat was examined for progressive abdominal distension. Radiography showed a fluid-containing cyst, which had subsequently ruptured as the result of a fall. Nephrectomy was performed, and examination revealed the coexistence of pyelocaliceal diverticula with a cystic intracapsular angiomyolipoma (mesenchymal hamartoma) in the left kidney. The diverticula were present on both cranial and caudal poles of the kidney and were lined by transitional epithelium. The hamartoma was characterized by the presence of multiple mesenchymal tissues, including thick-walled blood vessels, smooth muscle, and adipose tissue.