A Rare Cause of Lower Gastrointestinal Bleed: Internal Iliac Aneurysm With Rupture into Rectum

Abstract

An 85-year-old male with history of atrial fibrillation for which he was on warfarin, tobacco use, and vascular disease presented with acute onset of pulsatile rectal hemorrhage followed by unresponsiveness. Physical examination revealed confusion and tachycardia with a benign abdomen. Labs revealed a two-gram hemoglobin drop and INR of 5. The patient was resuscitated and coagulopathy was reversed. Enhanced CT abdomen/pelvis revealed a 2.2 x 1.8 cm distal right internal iliac artery aneurysm with contained rupture, evidenced by a 2.5 x 2.2 medially projecting pseudoaneurysm (Figure A). There was no enteric endoluminal extravasation of contrast to suggest a fistula, although presentation was suggestive of one. An urgent angiogram revealed an aneurysm arising from a distal branch of the anterior division of the right internal iliac artery, with no active extravasation (Figure B). Coil embolization of the outflow artery was performed (Figure C). The inflow artery to the aneurysm was then embolized and follow-up angiogram showed no additional feeding vessels into the aneurysm. Following the procedure, there was no further hematochezia and the hemoglobin remained stable. A literature search for ruptured internal iliac artery aneurysm with fistulization to the colon mainly showed cases occurring secondary to vasculitis or previous vascular reconstructive surgery. Primary fistulae occur most frequently between the aorta and esophagus or duodenum. Primary iliac-enteric fistulae are rare, occurring in about 0.07% of the general population.1 However, this is a possible cause of brisk lower gastrointestinal bleeding and should be considered in the differential of these patients. A small case series describing six patients with primary aorto/iliac-enteric fistulae found the overall 30-day mortality rate to be 50%.2 If there is suspicion for this, an enhanced CT scan should be obtained immediately as proceeding with endoscopic evaluation will only delay definitive therapy.FigureFigureFigure