History and Causes

Initial assessment of patients with all GIB should begin with the measurement of vital signs including heart rate and blood pressure (Figure 60.1). Concomitantly with resuscitation, a directed history and a focused physical examination relevant to LGIB should be performed.

The diverse causes of acute LGIB (Table 60.1) can be broadly divided among anatomic, vascular, inflammatory, and neoplastic etiologies. In patients younger than 50 years of age, hemorrhoids are the most common cause, whereas in older patients, diverticulosis and angiodysplasia (arteriovenous malformations) are most frequent. Rectal pain may indicate an anal fissure or hemorrhoids. Abdominal pain may indicate inflammatory bowel disease, ischemia of small or large bowel, or infectious colitis. Painless LGIB, especially in an elderly patient, should increase suspicion of diverticulosis or angiodysplasia. Pain exacerbated with meals can suggest chronic mesenteric ischemia, whereas pain exacerbated by defecation suggests an anal fissure.

The characteristics and color of the patient’s stool in acute LGIB also provide clues about the site of bleeding. Blood from the left side of the colon is typically bright red, whereas blood from the right colon is darker and mixed with stool. Blood on the outside of well-formed stool likely represents an anal canal or rectosigmoid lesion such as hemorrhoids or fissures. A change in bowel habits or stool caliber suggests neoplastic causes. If the patient has bloody diarrhea, consider inflammatory bowel disease or infectious colitis. Although hematochezia, the passage of bright red blood or blood clots per rectum, usually indicates an LGIB source, patients with massive UGIB may also present with hematochezia due to rapid transit of blood through the colon. Hematochezia, in combination with hemodynamic instability, should always raise the possibility of a UGIB. Similarly, LGIB from the distal small bowel or proximal colon can present as melena, or black, tarry stools, a finding typically associated with UGIB and thus an absolute diagnosis of the exact site or etiology of bleeding cannot be made based on the color and characteristics of stool.

Physical Examination

Physical examination may be helpful in determining the cause of LGIB. Pain out of proportion to the physical findings is suspicious for ischemia of the small bowel, colon, or both. In combination with a history of atrial fibrillation, recent myocardial infarction, pressor administration, or systemic hypotension, disproportionate abdominal pain suggests inadequate perfusion of the mesenteric arteries. Stigmata of chronic liver disease may indicate the existence of varices anywhere along the gastrointestinal tract, including the small intestine, colon, and rectum. Rectal examination may reveal a palpable rectal mass or visible fissures.

Management

Patients with LGIB should be admitted to the ICU if they meet appropriate clinical criteria of severity or concomitant disease (Table 60.2). Appropriate resuscitation efforts should be initiated, including large bore intravenous line placements, isotonic intravenous fluid infusions, and red blood cell transfusions. The target hemoglobin level depends on the patient’s age and comorbid conditions such as coronary artery disease, emphysema, and chronic kidney disease. For an elderly patient with significant comorbidities, the hemoglobin level should be maintained at 10 g/dL. If a patient has a coagulopathy (International Normalized Ratio [INR] > 1.5) or thrombocytopenia (platelets < 50,000/μL), these should be quickly addressed with transfusions of fresh frozen plasma and platelets, respectively. Vitamin K should be given to patients on warfarin in the setting of active GIB. Early in the management of these patients, a nasogastric lavage should be attempted at bedside to evaluate for a possible UGIB. An upper endoscopy should be considered in patients when a UGIB cannot be definitively excluded based on nasogastric lavage or other clinical information. This is particularly important in patients with hematochezia and hemodynamic instability. The surgical and interventional radiology services should be consulted if the patient has massive bleeding (requiring more than 6 units of blood) or develops signs of an acute surgical abdomen.

Diagnostic Evaluation