Obscure gastrointestinal bleeding localization using preoperative super-selective mesenteric angiography and intraoperative methylene blue injection: A case report and literature review

INTRODUCTION: Currently available diagnostic tests for localizing the source of gastrointestinal bleeding include esophagogastroduodenoscopy, colonoscopy, push enteroscopy, video capsule endoscopy, deep enteroscopy, nuclear scan, angiography, radiographic contrast studies of the small bowel, intraoperative enteroscopy, and computed tomography scanning. Despite these diagnostic modalities obscure gastrointestinal bleeding (OGIB) can be difficult to localize, making surgical intervention challenging. PRESENTATION OF CASE: We report the case of a 78-year-old patient who presented with OGIB, melena and passing bright red blood per rectum, with a hemoglobin of 4.8 g/dl requiring multiple blood transfusions. Initially the source of the bleeding was difficult to identify. Eventually, a preoperative superior mesenteric angiogram was performed, identifying an arteriovenous malformation (AVM) within the small bowel as the source of OGIB. Intraoperative methylene blue was then injected through the previously placed angiogram catheter to further localize the bowel segment with the lesion. DISCUSSION: Despite multiple diagnostic modalities, OGIB, especially originating in the small bowel, is challenging to localize, making surgical intervention difficult. Methylene blue is frequently used intraoperatively to properly identify anatomic landmarks. CONCLUSION: In cases of OGIB, superselective mesenteric angiography (SSMA) with intraoperative methylene blue injection can be used as an adjunct to routine diagnostic modalities to guide surgical interventions for controlling hemorrhage and for limiting the extent of bowel resection.