Secondary Aortoduodenal Fistula Caused On The Suture Line Of The Wrapping

To the Editor: Aortoenteric fistula (AEF) can cause fatal intestinal bleeding. Of all reported cases of AEF, 90% are known to be secondary to aortic surgery. Primary AEF is defined as a communication between the native aorta and the intestinal tract, and is a very rare lesion. Secondary AEF, however, is well known as a serious complication of abdominal aortic aneurysm (AAA) surgery. Secondary AEF has been classified into three types based on its morphology and each type has definitive clinical features. Nevertheless, all types of secondary AEF are fatal without surgical treatment. Most patients die of arterial bleeding, even if successfully diagnosed. This letter describes an autopsy case of secondary AEF, in which the fistula occurred on the suture line of the wrapping. The morphological type of this fistula is not included in the previous classification system. A Japanese man in his 70s complained of melena persisting for 13 days. His past history included mild diabetes mellitus, rheumatoid arthritis, arteriosclerosis obliterans and gastric ulcer. He had also had undergone graft replacement of an AAA 13 years earlier at another hospital. His health was under good control without medication before his last admission. Fourteen days before he was referred to Osaka City University Hospital, he was admitted to a local hospital complaining of melena. Emergency upper gastrointestinal (GI) endoscopy and colonoscopy could not detect any active bleeding site in the esophagus, stomach or colon. Due to persistent intestinal bleeding the patient was referred to Osaka City University Hospital for further investigation. On physical examination at admission, respiratory and heart sounds were normal, blood pressure was 124/60 mmHg, pulse 70 b.p.m. and regular. Laboratory tests indicated a lower level of hemoglobin (8.7 g/dL) and hematocrit (29.6%). He did not show any symptoms of infection. On capsule endoscopy and double balloon endoscopy there were no signs indicating either intestinal bleeding or the origin of bleeding. Four days after admission he developed hypovolemic shock following an episode of melena with back pain. Emergency colonoscopy showed multiple diverticulae and coagula in the ascending colon. He was treated with clipping for these colonic diverticulae to rule out bleeding from these sites. At this time there was no apparent bleeding in the transverse colon or ileum. Six days and 7 days after admission, colonoscopy and repeat abdominal arteriography (AAG) were respectively performed, but neither examination could identify the origin of intestinal bleeding. Communication between the aorta and intestine was not detected. After these examinations he vomited blood. Therefore, a second upper GI endoscopy and third AAG were performed, which showed that the duodenum was full of fresh blood, but physicians could not identify the site of bleeding. Despite intensive care for hypovolemic shock, he died 7 days after admission. During admission 30 units of packed red cells had been transfused. An autopsy was performed approximately 12.5 h after death. The body was 162 cm in height and weighed 62.6 kg. The stomach and intestine contained an estimated 1300 mL of blood. An area of adhesion measuring 2 ¥ 1.5 cm was noted between the third portion of the duodenum and the abdominal aorta. In this area there was an AEF measuring 2 mm in diameter. The aorta side of this fistula opened to a space between the graft and the native aneurysm wall, 5 mm distal from the proximal suture line (Fig. 1). The nonbifurcated graft was wrapped with aneurysm wall showing macroscopic suture lines on the proximal and distal sides that were firmly attached. The graft measuring 20 mm in diameter ¥ 90 mm length had shortened to 70 mm in length. The graft did not show dilation. The bilateral renal artery 30 mm proximal from the proximal suture line did not show either stenosis or dissection. The mucosal surface of the duodenum continuous with the fistula was intact. There was no diverticulum of the duodenum. The heart weighed 390 g and showed mild left hypertrophy. The coronary artery demonstrated arteriosclerosis, but there was no obstructive lesion. Ascites (100 mL) was yellowish and clear. Pleural effusion (left 50 mL; right 50 mL) was yellowish and clear. The bilateral kidneys showed severe arteriosclerotic nephrosclerosis. There were multiple colonic diverticulae in the ascending colon. Otherwise, we could not find tumor or ulcer in the large intestine. We incised the adhesion between the duodenum and aorta, and sliced the abdominal aorta horizontally into 3 mm sections, then embedded these in paraffin and stained the specimens with HE, Azan-Mallory, Elastica van Gieson with Alcian blue, and phosphotungstic acid hematoxylin (PTAH). The duodenal mucosa and muscular layer became continuous with the intimal layer of the aorta, forming the fistula (Fig. 2). Adjacent to this fistula, the cleft of the suture thread was confirmed. Thrombus in the fistula was fresh and sealed the lumen. There were scant intimal cells on the surface of thrombus. In the space between the graft composed of circular fibers and the aneurysm wall, there was multi-layered Pathology International 2009; 59: 598–600 doi:10.1111/j.1440-1827.2009.02414.x