We describe a case of intraparenchymal renal artery aneurysm in a 58-year-old normotensive man with a history of distal ureterectomy. Imaging studies of the pre-existing right renal mass had been interpreted as being consistent with a simple renal cyst. Three years after ureterectomy, a small parietal nodule with contrast enhancement developed within the cyst. Partial nephrectomy was carried out based on a preoperative diagnosis of cystic kidney cancer. Surprisingly, pathological diagnosis was an aneurysm with a revascularized thrombus. Even though the present case represents an extremely rare clinical manifestation of intraparenchymal renal artery aneurysm, clinicians should be aware that imaging studies cannot distinguish all instances of renal vascular disease.
© 2011 The Japanese Urological Association.