Optimal diagnostic approach for obscure GI bleeding

Obscure GI bleeding (OGIB) is defined as recurrent or persistent bleeding or iron deficiency anemia after negative findings on an initial evaluation and continues to be a challenging problem encountered by gastroenterologists. OGIB is frequently caused by a lesion in the small bowel beyond the reach of ordinary endoscopy, including EGD and colonoscopy. Capsule endoscopy (CE), which allows noninvasive visualization of the small-bowel mucosa, has revolutionized the evaluation of OGIB since its introduction in the early 2000s. Accordingly, CE is widely accepted as a first-line modality for the diagnosis of obscure GI bleeding (OGIB) because of its superior diagnostic yield, noninvasive nature, and higher chance to examine the entire small bowel in the medical guidelines of the 2000s. However, the potential miss rate of CE has been reported to be approximately 20% in the comparative study with double-balloon enteroscopy, and small bowel tumors are often reported to be overlooked in CE. In addition, capsule endoscopy may cause capsule retention due to occult obstructive lesions. With this background, the American College of Gastroenterology guidelines proposed in mid-2010 recommend that CE and cross-sectional imaging such as computed tomography (CT) enterography/magnetic resonance (MR) enterography can be performed complementary in OGIB patients suspected of small intestine bleeding, and no specific examination is suggested first. Meanwhile, OGIB treatment guidelines differ by country and region. The Korean guidelines suggest CE is an effective initial diagnostic method, and CT enterography / CT enteroclysis could be helpful as a complementary examination to CE when CE is contraindicated or If a small bowel neoplasm is suspected. On the other hand, Japanese guidelines recommend contrast-enhanced abdominal pelvic CT first, and if negative, CE or balloon-assisted enteroscopy is advised in OGIB. As described above, the initial diagnostic approach for OGIB shows some differences between countries. In OGIB patients with suspected small bowel bleeding, we need to find a way to present a more selected diagnostic modality according to the suspected lesion of the small bowel. In this talk, I would like to touch on the optimal diagnostic approach of OGIB.