In 2007, the American Gastroenterological Association proposed the following nomenclature to standardize terms used to describe chronic gastrointestinal blood loss :
- Occult bleeding refers to the initial presentation of a positive fecal occult blood test (FOBT) result and/or iron-deficiency anemia (IDA) when there is no evidence of visible blood loss to the patient or clinician.
- Obscure bleeding is defined as bleeding from the gastrointestinal (GI) tract that persists or recurs without an obvious etiology after upper endoscopy, colonoscopy, and radiologic evaluation of the small bowel (such as by small bowel follow-through or enteroclysis). Obscure bleeding is subdivided into overt or occult, depending upon the presence or absence of clinically evident bleeding.
The evaluation of patients with obscure-occult and obscure-overt bleeding will be reviewed here. The evaluation of patients with occult bleeding is discussed separately. (See "Evaluation of occult gastrointestinal bleeding".)
Obscure gastrointestinal bleeding accounts for approximately 5 percent of patients with gastrointestinal bleeding . In approximately 75 percent of these patients, the source is in the small bowel [3-6]. The remainder of cases are due to missed lesions in either the upper or lower gastrointestinal tract.
There are multiple potential causes of obscure gastrointestinal (GI) bleeding (table 1). Their relative frequency has not been well defined in large population-based studies, but probably depends upon age :