The origin of idiopathic renal arteriovenous malformation with giant twin aneurysms.

A 50-year-old female patient who presented with intermittent gross hematuria was referred to our hospital. Three-dimensional computed tomography (3D-CT) revealed a left renal arteriovenous malformation (AVM). Because she declined to undergo additional therapy including surgical treatment, we observed the clinical course of renal AVM for 7 years using 3DCT. When the 3D-CT showed gradual enlargement of the aneurysms concurrent with the onset of clinical symptoms (cardiomegaly and hypertension), we performed simple left nephrectomy. After the operation, the cardiomegaly and hypertension returned to normal, and gross hematuria did not recur. Based on the macro-anatomical findings of the resected kidney and the observation of the natural course, this case strongly supported the hypothesis that the renal AVM had existed from birth and enlarged gradually to eventually produce the typical signs and symptoms.