1664 A Herald Bleed: A Case Report of an Aortoenteric Fistula Causing an Acute Lower Gastrointestinal Bleed

Abstract

INTRODUCTION: Aortoenteric fistula (AEF) is a rare, life-threatening condition with an incidence of 0.007/million. Primary AEF arises de novo, secondary AEF (SAEF) occurs following abdominal aortic aneurysm (AAA) repair. Majority of AEF’s involve the duodenum, due to proximity to the aorta. It may present as an exsanguinating herald GI bleed, associated with high mortality rates. SAEF has a 45.8% mortality rate in the first month. CASE DESCRIPTION/METHODS: A 66-year-old female presented with sudden onset of large volume bright red blood per rectum (BRBPR). She denied any prior episodes of GI bleed, alcohol or NSAID use and had never had prior endoscopy. She mentioned cholecystectomy and hysterectomy as her only surgical interventions. On examination she was hemodynamically unstable, lethargic and had a midline abdominal scar. Digital rectal exam showed BRBPR. Her lab workup showed: Hgb 9.5, Hct 29%, platelets 147000, INR 1. An emergent EGD was negative. Colonoscopy showed a 5 cm, pulsatile submucosal mass with an actively bleeding ulcerated area. Epinephrine was injected for temporary hemostasis. A hemoclip was placed to mark the site for potential embolization, as the lesion was not amenable for definitive endoscopic intervention. A stat CT angiogram of the abdomen and pelvis revealed a large left external iliac artery (LEIA) pseudoaneurysm in the region of the clip placed during colonoscopy. Vascular surgery emergently placed a LEIA stent. It appeared the patient had an open aorto-bi-iliac bypass 15 years ago for a AAA which resulted in the development of SAEF. She did well post operatively. DISCUSSION: AEF is important to consider in older patients who present with large volume hematochezia. The presence of prior signs of abdominal surgery should raise suspicion for SAEF as it is difficult to diagnose because of its rarity. The commonest symptom of SAEF is gastrointestinal bleeding. Other symptoms are fever, sepsis, pulsating abdominal or groin mass, abdominal or back pain. CT and GI endoscopy are frequently used for diagnosis. Without treatment AEF often proves to be fatal. Treatment of AEF includes volume resuscitation, antibiotics, and aortic repair. Given our patient's bleed with tenuous clinical status, large body habitus, medical comorbidities, poor functional status as well as previous aorto-bi-iliac bypass, decision was made to approach the pseudoaneurysm endovascularly, despite possible presence of vessel-enteric fistula, as she was deemed unstable for an open approach.