Primary aortoenteric fistula: A case report and brief review of the literature

Abstract

Aortoenteric fistula is a life-threatening emergency and is associated with high morbidity and mortality. Prompt surgical intervention before the aneurysm ruptures lowers the mortality rate to about 50%. Potential imaging mimics for aortoenteric fistula include retroperitoneal fibrosis, mycotic aortic aneurysm, and infectious aortitis. Secondary aortoenteric fistula has relative higher incidence compared to primary and is more common with open aortic repair versus endovascular stent graft repair. Ectopic gas in the aneurysm sac and extravasation of enteric contrast into the aneurysm sac is diagnostic for aortoenteric fistula. However, enteric contrast is not recommended for routine evaluation of aortoenteric because the aforementioned finding is extremely rare. More common imaging findings include bowel loop appearing adherent to aneurysm sac with associated inflammatory stranding and foci or ectopic gas within the aneurysm sac or interposed between the bowel and aneurysm sac. Here we present a case of 52-year-old male who presents with incidental primary aortoenteric fistula.

Keywords: Acute aortic syndrome; Aortoenteric fistula; Axillobifemoral bypass.

Fig. 1

CT abdomen and pelvis with contrast was performed which showed infrarenal abdominal aortic aneurysm measuring 8.9 × 10.3 cm.

Fig. 2

Additionally, the thrombosed infrarenal abdominal aortic aneurysm demonstrated intramural air and was in close approximation to the proximal jejunum, findings compatible with primary aorto-enteric fistula. Of note: This was noted on retrospect at outside following aortobiiliac stent graft placement at outside facility (Fig. 3).

Fig. 3

Patient underwent endovascular aortobiiliac stent graft placement on the same day. Fluoroscopy imaging demonstrates no evidence of endoleak and appropriate position of the aortobiiliac stent.

Fig. 4

Five days following the procedure patient reported bright red blood per rectum with stable vitals and hematocrit. CT angiogram of the abdomen and pelvis was performed. Arterial phase (A, D and E), delayed phase (B) and unenhanced study (C and F). It showed normal positioning of aortobiiliac stent graft without evidence of endoleak. Stable size of the excluded aneurysmal sac. There was interval worsening of ectopic gas within the excluded aneurysmal sac. Findings compatible with known aortoenteric fistula.

Fig. 5

Prior to transfer, CT abdomen and pelvis with enteric contrast was performed which showed enteric contrast into the excluded aneurysmal sac, again confirming known aortoenteric fistula.

Fig. 6

Patient underwent resection of abdominal aortic aneurysm with a right axillary to bifemoral bypass utilizing bifurcated ringed Polytetrafluoroethylene.