Primary aorto-enteric fistula: A rare complication of abdominal aortic aneurysm
VS Thomson1, KG Gopinath2, E Joseph3, G Joseph1,
1 Department of Cardiology, CMC, Vellore, India
2 Department of Internal Medicine, CMC, Vellore, India
3 Department of Radiodiagnosis, CMC, Vellore, India
V S Thomson
Department of Cardiology, CMC, Vellore
A 70-year-old lady presented with recurrent gastrointestinal bleeding and septicemia caused by multiple enteric pathogens. She was diagnosed to have primary aorto-enteric fistula (PAEF) complicating abdominal aortic aneurysm. Endovascular aneurysm repair was carried out that arrested gastrointestinal bleeding, but despite prolonged antibiotic therapy the patient died a month later of probable sepsis. PAEF refers to abnormal communication between the aorta and the intestine resulting from disease at either site; this rare condition should be suspected in patients with abdominal aortic aneurysm who present with unexplained life-threatening gastrointestinal bleeding. Computerized tomography is the most sensitive investigation. Presence of ectopic gas adjacent to or within the aorta and of contrast within the gastrointestinal tract is the pathognomonic finding. Definitive treatment consists of surgical intervention, but it is associated with high risk in the acute setting. Endovascular therapy using stent-grafts is safe and effective in arresting gastrointestinal bleeding. However, it is frequently associated with recurrent sepsis even with continued antibiotic therapy, and should be considered as a bridge to more definitive surgical repair at a later time, after optimization of the patient«SQ»s condition.
|How to cite this article:|
Thomson V S, Gopinath K G, Joseph E, Joseph G. Primary aorto-enteric fistula: A rare complication of abdominal aortic aneurysm.J Postgrad Med 2009;55:267-269
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Thomson V S, Gopinath K G, Joseph E, Joseph G. Primary aorto-enteric fistula: A rare complication of abdominal aortic aneurysm. J Postgrad Med [serial online] 2009 [cited 2020 Apr 7 ];55:267-269
Available from: http://www.jpgmonline.com/text.asp?2009/55/4/267/58930
Aorto-enteric fistulas are abnormal communications between the aorta and intestine, and could be primary (occurring in the setting of disease process at either site), or secondary (after previous aortic surgery). Primary aorto-enteric fistula (PAEF) is ten times less common than the secondary variety and usually occurs as a complication of abdominal aortic aneurysm (AAA).  PAEF is characterized by its rarity (incidence 0.07% in large autopsy series)  presentation with massive gastrointestinal hemorrhage with or without sepsis, difficulty in diagnosing the condition, and rapidly fatal course if left untreated. ,, We present a classic case of PAEF that was diagnosed antemortem, in which endovascular therapy was carried out to arrest gastrointestinal bleeding.
A 70-year-old female presented to the emergency department with a short history of fever, lower abdominal pain and multiple episodes of hematemesis and malena. She was on treatment for diabetes mellitus, systemic hypertension and dyslipidemia, and also on immunosuppressive therapy for pemphigus vulgaris. She appeared pale, ill and dehydrated. There was sinus tachycardia (104/min) and hypotension (blood pressure 90/40 mmHg). Examination of the abdomen was unremarkable.
Investigations revealed severe anemia (hemoglobin 5.9 g/dl) and leukocytosis (white cell count 16,600/mm 3 ) with marked left shift. The platelet count (327 000/mm 3 ) and coagulation parameters were normal. Renal and liver function tests were normal except for low serum albumin (2 g/dl). The ESR (60 mm/hr) and C-reactive protein level (132 mg/l) were elevated. Chest radiograph revealed bilateral mild pleural effusions. Two-dimensional echocardiography was negative for vegetations. Computerized tomography revealed an infra-renal saccular AAA measuring 6.3 x 6.4 x 4.7 cm and large hematoma in the para-aortic region with small air pockets within [Figure 1]. Gastroduodenoscopy, done after initial stabilization of the patient, did not reveal active bleeding sites or other pathology. Four of six blood cultures grew Klebsiella species and one grew Salmonella typhimurium. Patient was treated with intravenous cefoperazone/sulbactam and ciprofloxacin in standard doses based on bacterial sensitivity and three units of packed red cells. A diagnosis of PAEF was made based on massive gastrointestinal blood loss, septicemia with two enteric pathogens, and para-aortic hematoma containing ectopic air in the presence of AAA. In view of the poor general condition and multiple co-morbidities, the patient was considered as 'high-risk for surgery' and was taken up for emergency aortic stent-graft deployment for arresting gastrointestinal blood loss. The procedure was done under local anesthesia using percutaneous right femoral arterial approach. In view of the abdominal aortic diameter (proximal and distal to the AAA) of 12mm, a 14 x 50 mm Wallgraft (Boston Scientific, Ireland) was deployed through a 12F sheath. This was reinforced with a 58 mm long, large-diameter peripheral stent-graft (Jostent, Abbot Vascular, Germany). The final angiogram showed effective sealing of the aneurysm sac with preserved flow in the abdominal aorta [Figure 2]. Two more units of blood were transfused post-procedure, after which the hemoglobin remained stable.
Intravenous antibiotic therapy was given for four weeks. Later, oral ciprofloxacin was continued. The ESR and C-reactive protein decreased to 35 mm/h and 55 mg/l respectively. The patient was discharged after six weeks in a stable afebrile condition, and was advised to continue oral ciprofloxacin for six months. However, she returned within 72 h with fever and vomiting. Clinical examination was unremarkable. Investigations revealed hemoglobin 11.3 g/dl and leukocytosis with left shift. The patient declined hospital admission and went home against medical advice where she died two days later of probable sepsis.
A large proportion of patients with PAEF die before a correct diagnosis is made, because the possibility of PAEF is not considered in view of its rarity. Absence of a single investigation that can reliably diagnose PAEF, lack of awareness and low index of suspicion on the part of the clinician also contribute to delay or lack of diagnosis.  Fatal exsanguination is usually preceded by less consequential "herald bleeding". A definitive diagnosis at this stage followed by timely referral for appropriate treatment could be life saving. , The typical triad of abdominal pain, pulsating mass, and gastro-intestinal hemorrhage is observed in only 11-27% of PAEF. , Recurrent septicemia with enteric pathogens is commonly seen in PAEF;  growth of multiple enteric organisms, as seen in our patient, increases the likelihood of PAEF. Gastroduodenoscopy is often negative and may delay appropriate management if a co-existent less significant source of bleeding is detected.  Conventional aortography seldom reveals the fistulous communication, but may be helpful in planning surgery or endovascular therapy.  Abdominal computed tomography is the investigation with highest sensitivity (61%); pathognomonic signs are ectopic gas adjacent to or within the aorta, and the presence of contrast within the gastrointestinal tract; bowel wall thickening overlying an aneurysm or disruption of the aortic fat cover are indirect signs; associated hematoma may be seen in the retroperitoneum or within the bowel wall or lumen. ,
Surgery is the definitive treatment for PAEF; the favoured technique consists of laparotomy, debridement, repair of the intestinal defect and in situ aortic bypass. However, an operative mortality of 30-40% has been reported. Extra-anatomic bypass is performed in patients with extensive local sepsis and is associated with even higher mortality.  Endovascular techniques can achieve rapid control of bleeding in PAEF, avoiding intervention in a hostile abdomen, and eliminating the complications associated with open surgery. However, placing new prosthetic material in an already infected field is a concern. A recent review found that 44% of such patients developed recurrent infection; this complication was more likely in patients who had evidence of sepsis pre-operatively, and resulted in worse 30-day and overall survival; importantly life-long antibiotic therapy did not reduce recurrent sepsis. ,, This fact was exemplified by our patient who showed initial improvement and stabilization, but subsequently succumbed to sepsis despite continuation of antibiotic therapy. Endovascular therapy should be considered as a bridge to more definitive surgical repair at a later time, after optimization of the patient's condition; our patient might have survived if this course of action had been followed.
We thank Mrs. Nandhini for secretarial help in preparation of the manuscript.
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