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Introduction
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Acute, overt lower gastrointestinal bleeding (LGIB) is described as hematochezia (passage of fresh blood from the anus, usually mixed with stool) originating from the colon or the rectum. LGIB ranges from scant bleeding to massive hemorrhage and is caused by a variety of anatomic, vascular, inflammatory or neoplastic conditions. LGIB accounts for approximately 20% of all gastrointestinal bleeding. Most cases of LGIB are self-limiting and can be electively evaluated on an outpatient basis. Patients with recurrent bleeding, hemodynamic instability, and significant comorbid conditions should be hospitalized and evaluated urgently.
Causes
Causes of severe LGIB can be categorized as anatomic (diverticulosis), vascular (angiodysplasia, ischemia, radiation-induced), inflammatory (inflammatory bowel disease, infection), or neoplastic (colon or rectal cancer) (Strate, 2023).
Initial Assessment
Obtain a history, physical exam, and laboratory tests to assess bleeding severity, location, and etiology. Fluid resuscitation should be performed concurrently.
- History
- Nature and duration of bleeding: hematochezia (red or maroon stool) is the predominant finding in acute LGIB. While melena (black, tarry stool) usually indicates upper GI bleeding, melena can also result from proximal colonic bleeding.
- Change in bowel habits, weight loss, and associated symptoms that may suggest a specific source (e.g., abdominal pain and diarrhea are suggestive of colitis)
- History of prior GI bleeds, abdominal and/or vascular surgeries, peptic ulcer or inflammatory bowel disease, or abdominopelvic radiation therapy
- Comorbidities, which may include cardiopulmonary, renal, or hepatic diseases
- Current medications, particularly those that increase bleeding risk such as nonsteroidal anti-inflammatory drugs (NSAIDs), antiplatelet agents, and anticoagulants
- Results or copies of previous studies, such as colonoscopy and endoscopy
- Physical exam
- Vital signs (including postural changes to assess for hypovolemia)
- Cardiopulmonary, abdominal, and digital rectal examinations to detect potential bleeding sources and determine the color of the stool
- Assessment for signs of circulatory shock such as altered mental status, diaphoresis, pallor, and dry mucous membranes
- Initial laboratory testing
- Complete blood count (CBC)
- Serum electrolytes
- Coagulation studies
- Type and crossmatch
Diagnosis
- Colonoscopy is the primary diagnostic modality (see below).
- Computed Tomographic Angiography (CTA) is now recommended for patients with severe LGIB, as it effectively identifies active bleeding sources and guides further management (Sengupta et. al, 2023).
- Hematochezia with hemodynamic instability may indicate an upper gastrointestinal bleed (UGIB) source, especially in high-risk patients (e.g., peptic ulcer or liver disease with portal hypertension, and patients on antiplatelet or anticoagulant medication).
- An upper endoscopy should be performed urgently, after volume resuscitation.
- Elevated blood urea nitrogen-to-creatinine ratio suggests an UGIB.
- For moderate suspicions of UGIB, nasogastric aspirate/lavage can be used to assess a possible upper GI source. Bloody aspirate necessitates an upper endoscopy before considering a colonoscopy.
- Risk factors for poor outcomes include the following:
- Hemodynamic instability (tachycardia, hypotension, and syncope)
- Ongoing bleeding (gross blood on initial digital examination and recurrent hematochezia)
- Comorbid illnesses
- Age greater than 60 years
- History of diverticulosis or angioectasia (vascular malformation)
- Elevated creatinine and anemia (initial hematocrit less than or equal to 35%)
- Patients should be triaged to ICU or medical floor based on hemodynamic status and presence of risk factors.