Genesis and pathophysiology of lower gastrointestinal bleeding

Abstract.

The incidence of lower gastrointestinal bleeding (LGB) is estimated to be 20–30 per 100,000 of the adult population at risk, which is clearly correlated with increasing age. The problem of LGB is identification of the bleeding source. LGB stops spontaneously in 80% of cases, but 10% of bleeding sources cannot be identified, and rebleeding occurs in 25%. The quality of LGB – hematochezia, melena, or occult bleeding – may point to the region of the bleeding source, as patient age is correlated with specific pathologies. In many patients, LGB is a leading symptom of a chronic disorder. Most acute peranal bleeding arises from the colon (80%) with colonic diverticula and angiodysplastic lesions as the most frequent reasons. In 5% of cases, LGB is caused by disorders of the small bowel, in most cases due to small-bowel tumors or to Meckel's diverticulum in younger patients. In 15–20%, acute peranal bleeding is caused by lesions in the upper gastrointestinal tract. The intensity of LGB determines the urgency of identification of the bleeding source; however, chronic occult blood loss superimposed by melena may place the patient at risk as early as a patient with hematochezia. Therefore, prompt resuscitation is required in many LGB patients before diagnostic procedures are initiated.