Spontaneous aortocaval fistula secondary to ruptured abdominal aortic aneurysm.

Two patients with the rare condition of spontaneous aortocaval fistula secondary to ruptured abdominal aortic aneurysm were treated successfully by surgical closure of the fistula. In view of the existing controversies on certain aspects of the pathophysiology involved, canine experiments were performed to elucidate the pathogenesis of regional venous hypertension and hematuria observed in these patients. The experiments demonstrated that regional venous hypertension is a purely rheologic phenomenon and that hematuria originates from a congested lower urinary tract.