Primary aortoenteric fistula.

ABSTRACT

We describe a case of primary aortoenteric fistula (PAEF) in a patient with upper gastrointestinal bleeding. Primary aortoenteric fistula is a rare but clinically important cause of catastrophic gastrointestinal bleeding. The diagnosis of PAEF is difficult and sometimes not made until laparotomy. Primary aortoenteric fistula should be considered in any patient known to have an abdominal aortic aneurysm who presents with upper gastrointestinal bleeding when no identifiable source of bleeding is found on upper endoscopy. Computed tomography may confirm the diagnosis and emergency exploratory laparotomy should be done as soon as the diagnosis is considered clinically.

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PRIMARY AORTOENTERIC FISTULA (PAEF) is a rare but clinically important cause of catastrophic upper gastrointestinal hemorrhage. A review of literature reveals that of the nearly 250 cases of PAEF reported, only 112 patients were treated with emergency laparotomy. Only 59 patients were reported to be alive and well at their most recent follow-up. (1) These results illustrate the difficulty in establishing an early diagnosis and show that failure to do so results in high mortality. A large autopsy series reported an incidence of 0.04% to 0.07% of PAEF occurring in 0.69% to 2.36% of patients with an aneurysm of the abdominal aorta. (2) Secondary aortoenteric fistulas, or fistula formation after surgical repair of an abdominal aortic aneurysm, have been reported to occur in 0.4% to 4.0% of patients. (3,4) We report a case of PAEF in a 43-year-old man.

CASE REPORT

A 43-year-old African American man with a history of alcohol abuse had an episode of bright red emesis and melena. He subsequently lost consciousness and was found diaphoretic by paramedics. The patient was taken to the emergency room where he was found to have hypotension (blood pressure 80/20 mm Hg and tachycardia (pulse rate 120/min). The patient was resuscitated with intravenous fluids and transfusion of 2 units of packed red blood cells. His medical history included a previous episode of pancreatitis 9 years before this admission. He had had no previous episodes of hematemesis, abdominal pain, or melena and no abdominal surgery. He was taking no medications. On admission to our hospital, physical examination showed pallor, and the abdominal examination was unremarkable with absence of surgical scars or palpable masses. The hemoglobin value was 10 g/dL and mean corpuscular volume 82 fL. Coagulation parameters were normal.

Emergency esophagogastroduodenoscopy revealed a large blood clot in the fundus and upper body of the stomach that prevented adequate inspection of this area but was otherwise unremarkable. Blood in the duodenum and antrum was cleansed with irrigation. Twenty-four hours later, the patient had recurrent bleeding and required transfusion of 2 additional units of packed red blood cells. Repeated upper endoscopy did not show blood in the stomach or duodenum, but no source of bleeding could be found. There was no appreciable external luminal compression of the distal duodenum. Computed tomography (CT) of the abdomen showed a 6.0 x 7.5 cm contained rupture (Figure) of the left anterolateral aspect of the aorta, with intravenous contrast material present outside of the aortic intima.

Thirty-six hours after admission, the patient had another episode of hypotension and melena. Exploratory laparotomy revealed an abdominal aortic aneurysm adherent to the distal duodenum and the first portion of the jejunum. An aortoduodenal fistula was identified in the proximal jejunum. There was no evidence of enteric contamination, and peritoneal culture and Gram's stain showed no bacteria. Aorta-to-aorta graft and fistula repair were done. Gram's stain and cultures of the aortic wall were negative. Pathology showed atheromatous material and blood clot.

The patient had an uneventful postoperative course and was discharged 15 days after admission. When last seen in follow-up at 2 months, he was clinically well and without signs of infection.

DISCUSSION

Fistula formation between the aorta and the intestinal tract was first described in 1839 in reference to a man with a "pulsating tumor ... and a discharge of blood by stool," who died suddenly. At autopsy, it was noted that "the jejunum had adhered to ... the aneurismal bag and that sac had ulcerated into the intestine." (5) Communications between the aorta and the intestine resulting from disease at either site are referred to as primary aortoenteric fistulas. Fistulas occurring after aortic reconstructive surgery, also called aortic graft--enteric fistulas, are considered secondary aortoenteric fistulas. Before 1960, the most common cause of abdominal aortoenteric fistulas was aortic aneurysm, followed by infectious aortitis due to syphilis or tuberculosis. (6,7) However, over the past three decades or so, erosion of the intestine by prosthetic vascular grafts has become a much more common cause, with an incidence of up to 4%. (8)

Primary aortoenteric fistula is rare and is usually caused by an untreated abdominal aortic aneurysm. (9,10) It is often discovered unexpectedly during exploratory laparotomy and is usually not considered as a presumptive preoperative diagnosis. (11) The third portion of the duodenum, being fixed retroperitoneally and in proximity to the descending aorta, is the bowel segment most vulnerable to vascular impingement. The process originates when ischemia and subsequent necrosis of the intestinal wall occur as a consequence of repetitive traumatic pulsations of an adjacent aortic aneurysm. Subsequent rupture of an expanding aneurysm or perforation of the aorta as a result of contamination with gastrointestinal contents results in the formation of a communication with the bowel and the potential for rapid exsanguination. Bacterial, syphilitic, and tuberculous forms of aortitis are rare infectious causes of this type of fistula. Carcinoma, radiotherapy, peptic ulcer, gallstones, diverticula, and foreign bodies hav e all been implicated as causes of fistula formation. (12,13)

Although the typical symptoms of PAEF consist of abdominal pain, gastrointestinal hemorrhage and a pulsatile abdominal mass, this classic triad of symptoms can be found in only 23% of the patients. (14) The characteristic picture is of a "herald" hemorrhage followed hours, days, or weeks later by catastrophic hemorrhage. The herald bleeding is the result of a small fistula tamponaded by thrombus formation. If the fistula continues to expand or the occluding thrombus is removed, massive hemorrhage results. Since 70% of patients survive at least 6 hours after the initial bleeding episode and up to 50% survive 24 hours, a herald hemorrhage should be viewed as an opportunity for prompt intervention. (15)

An aggressive diagnostic workup and a high index of suspicion are required for successful outcome in cases of PAEF. Endoscopy of the upper gastrointestinal tract should be strongly considered as the first step in diagnosis. The sensitivity of upper gastrointestinal endoscopy in detecting aortoenteric fistula is unknown, but this technique probably identifies less than half of cases. However, endoscopy may disclose another cause of bleeding (bleeding peptic ulcer with stigmas of recent bleeding). By no means do normal findings or positive findings of gastritis or ulcers without active bleeding rule out aortoduodenal fistula. Careful inspection of the distal duodenum should be done in the setting of unexplained torrential bleeding. (16) Computed tomography with contrast is the most suitable diagnostic test when an aortoenteric fistula is suspected. (17) The CT may show an abnormal communication between the aorta and the bowel or may disclose loss of continuity of the aneurysmal wall and air bubbles in the aneur ysm wall that are pathognomonic for the existence of a fistula. (18, 19) Percutaneous angiography may be considered but is rarely of value since most patients are critically ill when the decision for angiography is made. (20)

Emergency exploratory laparotomy should be done as soon as the diagnosis is considered clinically. (21) Mortality is 100% without surgical intervention. Current recommendations for treatment without evidence of gross contamination are for culture and debridement of the aneurysmal aorta, repair with an in situ rifampicinsoaked prosthetic graft, and a primary repair of the gastrointestinal tract. (1) Postoperatively, the patient should be treated with broad spectrum antibiotics. If the cultures are positive, antibiotic therapy should be continued for 4 to 6 weeks. (1)

CONCLUSION

The diagnosis of PAEF is difficult and sometimes not made until exploratory laparotomy. The diagnosis should be considered in any patient known to have an abdominal aortic aneurysm and who exhibits upper gastrointestinal bleeding when no source of bleeding is seen in upper endoscopy. Computed tomography may confirm the diagnosis. Exploratory laparotomy should be done as soon as the diagnosis is contemplated to decrease the high mortality rate.

References

(1.) Brown PW, Sailors DM, Headrick JR, et al: Primary aorto-jejunal fistula: a case report. Am Surg 1999; 65:139-141

(2.) Taheri SA, Kulaylat MN, Grippi J, et al: Surgical treatment of primary aortoduodenal fistulae. Ann Vase Surg 1991; 5:265-270

(3.) Hickey NC, Downing R, Hamer JD, et al: Abdominal aortic aneurysms complicated by spontaneous ileocaval or duodenal fistulae. J Cardiovasc Surg 1991; 32:181-185

(4.) Olcott C IV, Holcroft JW, Stoney RJ, et al: Unusual problems of abdominal aortic aneurysms. Am J Surg 1978; 135:426-431

(5.) Diethrich EB, Campbell DA, Brandt RL: Gastrointestinal hemorrhage, presenting symptom of aortoduodenal fistulization. Am J Surg 1966; 112:903-907.

(6.) Reckless JP, McColl I, Taylor GW: Aortoenteric fistulae: an uncommon complication of abdominal aortic aneurysm. Br J Surg 1972; 59:458-460

(7.) Grande JP, Ackerman DM, Edwards WD: Aortoenteric fistulas: a study of 28 autopsied cases spanning 25 years. Arch Pat pathol Lab Med 1989; 113:1271-1275

(8.) Blunt TJ: Synthetic vascular graft infections, secondary graft enteric erosion and graft enteric fistulas. Surgery 1983; 94:1-9

(9.) Yao JST, Pearce WH: Arterial Surgery, Management of Challenging Problems. Stamford, Conn, Appleton and Lange, 1996, pp 209-221

(10.) Rutherford RB: Vascular Surgery. Philadelphia, WB Saunders Co, 4th Ed, 1995, pp 611-619

(11.) Voorhoeve R, Moll FL, DeLetter J AM, et al: Primary aortoenteric fistula: report of eight new cases and review of the literature. Ann Vase Surg 1996; 10:40-48

(12.) Bergqvist D: Arterioenteric fistula. review of a vascular emergency. Acta Chir Scand 1987; 153:81-86

(13.) Estrada FP, Tachovsky TJ, Orr RM, et al: Primary aortoduodenal fistula following radiotherapy. Surg Gynecol Obstet 1983; 156:646-650

(14.) Voorhoeve R, Moll FL, Bast TJ: The primary aortoenteric fistula in the Netherlands--the unpublished cases. Eur J Vasc Endovasc Surg 1996; 11:429-431

(15.) Dachs RJ, Berman J: Aortoenteric fistula. Am Fam Physician 1992; 45:2610-2616

(16.) Nagy SW, Marshall JB: Aortoenteric fistulas recognizing a potentially catastrophic cause of gastrointestinal bleeding. Postgrad Med 1993; 93:211-222

(17.) Korkut AK, Arpinar E, Yasar T, et al: Primary aortoduodenal fistula complicated by abdominal aortic aneurysm. J Cardiovasc Surg 2000; 41:113-115

(18.) Daly CA, Nott DM, Padley SP: Aortoduodenal fistula: appearances on computed tomography. Aust N Z J Surg l997; 67:745-746

(19.) Ibrahim IM, Raccuia JS, Micale J, et al: Primary aortoduodenal fistula. diagnosis by computed tomography. Arch Sing 1989; 124:870-871

(20.) Yeong KY: Angiographic demonstration of primary aortoenteric fistula. a case report. Ann Acad Med Singapore 1995; 24:467-469

(21.) Van Der Klooster JM, Reuters RA, Van Der Wiel HE: Primary aortoduodenal fistula. Neth J Med 1999; 54:152-157

RELATED ARTICLE: KEY POINTS

* The diagnosis of primary aortoenteric fistula should be considered in any patient known to have abdominal aortic aneurysm with upper gastrointestinal bleeding of unexplained etiology.

* A "herald bleeding' is an opportunity for prompt intervention

* Endoscopy is the first step in diagnosis. Computed tomography may confirm the diagnosis.

* Emergency exploratory laparotomy should be done as soon as the diagnosis is considered.

From the Departments of Medicine and Surgery, Southern Illinois University School of Medicine; and the Department of Radiology, St. John's Hospital, Springfield, Ill.

Reprint requests to Edgard A. Cumpa, MD, 700 S Durkin Dr, Apt 351, Springfield, IL 62704.