an aortoenteric fistula ( aef ) is a rare but life - threatening cause of gastrointestinal ( gi ) bleeding . patients with an aef are commonly encountered as a medical emergency associated with acute gi bleeding . although the reported incidence of aef is low , immediate recognition and management is essential for the patient 's survival . aef can be classified into primary and secondary types according to the presence or absence of a prior history of aortic surgery ( 1 ) . two major concerns for the treatment of aef are bleeding control at the time of the initial presentation and the prevention of late complications associated with bleeding or infection . early diagnosis and a variety of surgical procedures have been performed to reduce the incidence of postoperative infectious complications . these include an aortic resection followed by an axillo - bifemoral bypass ( axbfb ) ( 2 ) , in situ aortic reconstruction using a prosthetic graft , antibiotic - impregnated prosthetic graft ( 3 ) , autogenous femoral vein graft ( 4 ) , or cryopreserved aortic allograft ( 5 , 6 ) . the medical records of five consecutive patients ( all male , mean age 659.2 yr , range 55 - 76 yr ) , who were treated for an aef ( four primary and one secondary aef ; four aortoduodenal and one aortogastric fistula ) between march 1999 and february 2003 were retrospectively reviewed . preoperatively , intravenous contrast - enhanced abdominal computed tomography ( ct ) scans were performed in all patients . gastroduodenal fiberscopic examination was performed in one patient , but the bleeding focus could not be located due to a large hematoma in the stomach . for bacterial culture , intraoperative tissue culture with periaortic tissue around the aef , and postoperative drain fluid culture were obtained in all patients . for the arterial blood flow reconstruction , axbfb after the aortic aneurysmectomy was done in two patients and an in situ aortic reconstruction was performed in three patients . the procedures were selected according to the surgical findings ; axbfb for patients with periaortic purulence and an in situ aortic reconstruction for those with no evidence of gross purulence . after periaortic debridement and irrigation with 1% povidone iodine solution , the aortic stump or aortic prosthetic graft was covered with the greater omentum . the greater omentum was dissected from its attachment to the transverse colon and mobilized to the infrarenal aorta through an opening at the transverse mesocolon . before closing the abdominal wall , closed suction drains were placed around the site of the infrarenal abdominal aorta . postoperatively , intravenous antibiotics were given for four weeks followed by oral antibiotics for two months or longer . the selection of antibiotics depended on the results of the bacterial cultures from the blood , retroperitoneal tissue , and peritoneal drainage fluid . all patients were male with a mean age of 66 yr and presented with acute gi bleeding to the emergency department . the time interval between the herald bleeding and the episode of large gi hemorrhage was 2.5 hr ( median , range 1 - 48 hr ) . the underlying causes of the aef were an aortic aneurysm ( three patients with infrarenal abdominal aortic aneurysm [ aaa ] and one patient with type iv thoracoabdominal aneurysm ) and one para - anastomotic pseudoaneurysm in a patient who underwent an aortobifemoral bypass graft eight years earlier due to chronic aortoiliac occlusive disease . table 2 summarizes the surgical findings and procedures . in a patient with an aortogastric fistula , gastric fistula opening was located at the posterior wall of the gastric cardia close to the esophagocardial junction . a retrospective review of the preoperative abdominal ct scans revealed periaortic air shadows in four ( 80% ) patients ( fig . this patient was treated with a sigmoid colectomy and hartmann 's colostomy before axbfb grafting . table 3 shows the bacteriologic examination results . a postoperative gastropleural fistula ( gpf , fig . 2 ) developed in a patient with taa , and the aortogastric fistula required a second operation to close the gastric fistula and thoracotomy tube for drainage . no mortality or graft infection developed during the follow - up period ( mean 40 months ; range , 24 months to 68 months ) ( table 4 ) . aef can occur as a rare late complication of aortic reconstructive surgery , or even less frequently , as a complication of an untreated aaa ( 7 ) . the optimal management for aef consists of an early diagnosis before the occurrence of major bleeding , prompt bleeding control by expeditious control of the proximal aorta , closure of the enteric fistula without spilling of the bowel contents , a durable arterial reconstruction , and the prevention of postoperative complications , particularly graft infection . the role of the primary physician in the emergency department is important for early detection of aef . although gi hemorrhage , abdominal pain , and a pulsatile abdominal mass are the diagnostic triad of aef , the signs of a pulsatile abdominal mass can be masked by abdominal distension . capaldo and amin ( 8) reported abdominal pain and a pulsatile mass in 32% and a pulsating abdominal mass in 25% of their aef patients . herald bleeding occurred in 60% of our patients , and the time interval between the initial bleeding and the massive gi hemorrhage ranged from one hour to two days , which is similar to other reports ( 1 , 8 , 9 ) . theoretically , this window period provides an opportunity to perform definitive surgical treatment for the aef . currently , intravenous contrast - enhanced abdominal ct can be easily performed in an emergent situation . spiral ct provides not only diagnostic clues for an aef but also anatomical information for later aortic surgery . intravenous contrast- enhanced abdominal ct has been recommended as an initial diagnostic test for aef ( 1 , 3 , 6 , 9 ) . the ct findings suggestive of aef are air bubbles around the aorta , bowel wall edema around the aorta , the loss of a fatty plane between the aorta and gi tract , and rarely , visualization of the fistula itself . of these findings , a periaortic air shadow was reported to be a specific finding for the diagnosis of an aortic graft infection or aef ( 10 , 11 ) . periaortic air shadows were found in 80% of patients by a retrospective review of the preoperative abdominal ct scans . in order to reduce the risk of infectious complications such as a graft infection , retroperitoneal debridement and irrigation with an antiseptic solution was performed and pedicled omentum was used to cover up the aortic stump or aortic graft . there has been some debate regarding the optimal arterial reconstruction procedure after removing the infected aneurysm or aortic graft in patients with an aortic graft infection or infected aortic aneurysm , and either an in situ aortic reconstruction ( 1 , 12 ) or axillobifemoral bypass grafting have been proposed ( 1 , 7 , 9 ) . in previous reports , ( 3 , 5 , 9 ) the great omentum was used to wrap around the prosthetic graft or cover the infected surgical field for the purpose of preventing a graft infection . however , there have been no randomized clinical studies demonstrating the anti - bacterial effects of omental tissue to date . regarding the duration of postoperative antibiotic therapy , saers and scheltinga ( 1 ) recommended at least 1 week of antibiotic therapy following negative blood culture and 4 to 6 weeks of systemic antibiotic therapy if blood cultures were positive . the duration of antibiotic therapy can be determined by the results of blood culture and clinical findings of the patients . in a primary aef , chronic mechanical irritation between the bowel wall and aneurismal wall appears to provide watertight adhesion between the two tissue planes . to our knowledge , high - pressure aortic blood can create a one - way fistula into the bowel lumen and massive arterial bleeding can clean the bowel lumen . these properties of primary aef might be associated with the lower rate of graft infection after an in situ aortic reconstruction . in summary , early diagnosis and prompt surgical treatment are essential steps for an improved treatment outcome . for the early diagnosis of an aef , intravenous contrast - enhanced abdominal ct imaging can provide a rapid and effective diagnosis even in an emergent situation . while there is no optimal surgical procedure for aef to date , the most appropriate procedure can be selected based on the surgical findings , underlying cause of the aef , and patient status . however , further studies will be needed to determine the efficacy of the omentum in preventing infections .