Review article: the diagnosis and investigation of obscure gastrointestinal bleedingK. Liu, A. J. Kaffes. Alimentary Pharmacology & Therapeutics 2011, 34: Article first published online: 21 JUN 2011 Background Obscure gastrointestinal bleeding (OGIB) is a commonly encountered clinical problem in gastroenterology and is associated with significant morbidity and mortality. The investigation and management of OGIB has changed dramatically over the past decade with the advent of newer gastroenterological and radiological technologies. Aim To review the current evidence on the diagnosis and investigation of OGIB. Methods We searched the PubMed database (1985–2010) for full original articles in English-language journals relevant to the investigation of OGIB. The search terms we used were ‘gastrointestinal bleeding’ or ‘gastrointestinal hemorrhage’ or ‘small bowel bleeding’ each in combination with ‘obscure’, or ‘capsule endoscopy’, or ‘enteroscopy’ or ‘enterography’ or ‘enteroclysis’. Results Capsule endoscopy (CE) or double balloon enteroscopy (DBE) should be first line investigations. They are complimentary procedures with comparable high diagnostic yields. DBE is also able to provide therapeutic intervention. Newer technologies such as single balloon and spiral enteroscopy are currently being evaluated. Radiological and nuclear medicine investigations, such as CT enterography and CT enteroclysis, are alternative diagnostic tools when CE or DBE are contraindicated. Repeating the gastroscopy and/or colonoscopy may be considered in selective situations. An algorithm for investigation of obscure bleeding is proposed.Conclusions The development of capsule endoscopy and double balloon enteroscopy has transformed the approach to the evaluation and management of obscure gastrointestinal bleeding over the past decade. Older diagnostic modalities still play a complementary, but increasingly selective role.