Obscure gastrointestinal bleeding (OGB) is defined by consensus as a persistent or recurrent one in which it is not possible to identify its origin after an upper endoscopy (UE) and a colonoscopy have been carried out, and some authors also add to these the radiographic examination of the small bowel transit with conventional barium or enteroclysis. This term covers two distinct categories depending on how the bleeding externalizes. On one side it is possible to identify the occult OGB, in which bleeding would be evident only by measuring occult blood in stool, with or without iron deficiency, and on the other, the overt OGB with clinically evident bleeding present as hematochezia or melena.
Gastrointestinal bleeding has traditionally been classified as upper and lower according to the location of the origin of bleeding, depending on whether the cause was proximal or distal to the ligament of Treitz. This classification has been maintained until relatively recently due to the difficulties in the diagnostic evaluation of the small bowel, because its length, layout and peristalsis. The development of new diagnostic and therapeutic procedures such as capsule endoscopy (CE) and double balloon enteroscopy (DBE), forced to revise this classification. Thus, the terms upper gastrointestinal bleeding (of origin proximal to the papillary region, accessible by UE), mid-gastrointestinal bleeding (from the papilla to the ileocecal valve, as assessed by CE and EDB) and lower gastrointestinal bleeding (originated in the colon and assessed mainly through colonoscopy) are considered most suitable nowadays. Then, an evident case of gastrointestinal bleeding in which the UE and colonoscopy did not identify the cause, would be classified as a mid-gastrointestinal bleeding, always having the obligation to rule out a lesion in the small bowel.
This review will deal with the diagnostic and therapeutic management of patients with overt OGB, analyzing the performance of procedures available today ending with a proposal for a sequence of clinical interventions.