Lower gastrointestinal bleeding

Lower gastrointestinal bleeding (LGIB) is any form of gastrointestinal bleeding in the lower gastrointestinal tract. LGIB is a common reason for seeking medical attention at a hospital's emergency department. LGIB accounts for 30–40% of all gastrointestinal bleeding and is less common than upper gastrointestinal bleeding (UGIB). It is estimated that UGIB accounts for 100–200 per 100,000 cases versus 20–27 per 100,000 cases for LGIB. Approximately 85% of lower gastrointestinal bleeding involves the large intestine, 10% are from bleeds that are actually upper gastrointestinal bleeds, and 3–5% involve the small intestine.

A lower gastrointestinal bleed is defined as bleeding originating distal to the ileocecal valve, which includes the colon, rectum, and anus. LGIB was previously defined as any bleed that occurs distal to the ligament of Treitz, which included the aforementioned parts of the intestine and also included the last 1/4 of the duodenum and the entire area of the jejunum and ileum. This has been divided into middle gastrointestinal bleeding (from the ligament of Treitz to the ileocecal valve) and lower gastrointestinal bleeding which involves a bleed anywhere from the ileocecal valve to the anus.

The stool of a person with a lower gastrointestinal bleed is a good (but not infallible) indication of where the bleeding is occurring. Black tarry appearing stools medically referred to as melena usually indicates blood that has been in the GI tract for at least 8 hours. Melena is four-times more likely to come from an upper gastrointestinal bleed than from the lower GI tract; however, it can also occur in either the duodenum and jejunum, and occasionally the portions of the small intestine and proximal colon. Bright red stool, called hematochezia, is the sign of a fast moving active GI bleed. The bright red or maroon color is due to the short time taken from the site of the bleed and the exiting at the anus. The presence of hematochezia is six-times greater in a LGIB than with a UGIB.

Occasionally, a person with a LGIB will not present with any signs of internal bleeding, especially if there is a chronic bleed with ongoing low levels of blood loss. In these cases, a diagnostic assessment or pre-assessment should watch for other signs and symptoms that the patient may present with. These include, but are not limited to, hypotension, tachycardia, angina, syncope, weakness, confusion, stroke, myocardial infarction/heart attack, and shock.

The following are possible causes of a LGIB:

Diagnostic evaluation must be performed after patients have been adequately resuscitated. If an upper GI source is suspected, an upper endoscopy should be performed first. Lower gastrointestinal series evaluation can be performed with anoscopy, flexible sigmoidoscopy, colonoscopy, rarely barium enema, and various radiologic studies.

The history in these patients should focus on factors that could be associated with potential causes: blood coating the stool suggests hemorrhoidal bleeding while blood mixed in the stool implies a more proximal source; bloody diarrhea and tenesmus is associated with inflammatory bowel disease while bloody diarrhea with fever and abdominal pain especially with recent travel history suggests infectious colitis; pain with defecation occurs with hemorrhoids and anal fissure; change in stool caliber and weight loss is concerning for colon cancer; abdominal pain can be associated with inflammatory bowel disease, infectious colitis, or ischemic colitis; painless bleeding is characteristic of diverticular bleeding, arteriovenous malformation (AVM), and radiation proctitis; nonsteroidal anti-inflammatory drug (NSAID) use is a risk factor for diverticular bleeding and NSAID-induced colonic ulcer; and recent colonoscopy with polypectomy suggests postpolypectomy bleeding. Patients should be asked about symptoms of hemodynamic compromise, including dyspnea, chest pain, lightheadedness, and fatigue.

Orthostatic hypotension implies at least a 15% loss of blood volume and suggests a more severe bleeding episode. Evaluate for abdominal tenderness, masses, and enlargement of the liver and spleen. Additional key elements include a careful and thorough inspection of the anus, palpation for rectal masses, characterization of the stool color, and a stool guaiac card test to evaluate for the presence of blood.^{[citation needed]}