Evaluation of the guaiac-positive patient

Abstract

One of the more common encounters a physician must deal with is the presence of occult gastrointestinal blood loss. The prevalence may reach up to 1 in 20 adults. The detection of occult blood is important because a person may lose up to 150 ml of blood from the proximal gastrointestinal tract before producing overt melena [Schiff et al. Am J Med Sci 203:409, 1942]. Before proceeding further, an important distinction must be made between occult gastrointestinal blood loss and obscure gastrointestinal bleeding.