Acute severe lower GI bleeding occurs with an annual hospitalization rate of 22 per 100,000 adult population; this is based on a retrospective study of middle-class Americans who were members of Kaiser Permanente Health Care system in San Diego, California.¹ Assuming that an average full-time clinical gastroenterologist is responsible for 50,000 adult lives, he or she would see more than 10 cases per year. Most cases occur in elderly patients, given the increased frequency and risk for diverticulosis, vascular disease, and colonic malignancy.¹ Risk of lower GI bleeding is also associated with the use of aspirin and nonsteroidal antiinflammatory drugs (NSAIDs).^2,³

Initial Approach to a Patient with Severe Hematochezia

Initial patient assessment includes history, vital signs with orthostatic blood pressure determination, and physical and rectal examinations. Patients should be asked about whether they saw red blood or dark maroon blood, duration of symptoms, abdominal pain, prior history of lower GI bleeding, prior pelvic radiation, history of diverticulosis, and prior colon imaging studies. Patients should also be asked about use of medications associated with GI bleeding (e.g., aspirin, NSAIDs, anticoagulants, and Ginkgo biloba). Weight loss or a change in bowel habits suggests possible colon cancer. Abdominal pain usually suggests ischemic colitis, although abdominal pain can be present in other colitides and malignancy.

The most important parts of the physical examination are the vital signs and the stool examination. The presence of bright red blood on rectal examination strongly suggests the possibility of colonic bleeding. Bright red blood per rectum is always a colonic source, unless it is accompanied by hypotension, which can occur during a severe upper GI or small bowel bleed with rapid transit of blood.⁴ In the setting of hematochezia without hypotension, placement of a diagnostic nasogastric (NG) tube is usually unnecessary because it is unlikely that there is a severe upper GI bleed without hypotension. If there is hypotension and hematochezia, a severe upper GI bleed is possible, and an NG tube should be placed. A clear NG tube lavage does not always imply a lower GI source because 16% of patients with duodenal ulcer bleeds have negative NG lavage.⁵ If bile is seen in the NG tube lavage, it is unlikely to be an upper GI bleed. Physical examination should also focus on abdominal tenderness, surgical scars, and stigmata of liver disease. Most patients with severe hematochezia do not need placement of an NG tube for diagnostic lavage, unless there is a strong suspicion for an upper GI source. At least one large-bore (14-gauge or 16-gauge) intravenous catheter should be placed, with two placed in the setting of ongoing bleeding.

Blood should be sent for hematocrit, platelets, prothrombin time, partial thromboplastin time, chemistry panel, and type and crossmatch for packed red blood cells. Resuscitation should be initiated simultaneously with assessment. Normal saline is infused as fast as needed to keep systolic blood pressure greater than 100 mm Hg and pulse lower than 100 beats/min. Patients are transfused with packed red blood cells, platelets, and fresh frozen plasma as necessary to maintain hematocrit greater than 24%, platelet count greater than 50,000/mm³, and prothrombin time less than 15 seconds. A GI endoscopist should be notified as soon as possible to expedite patient diagnosis and possible therapy; this is especially important in terms of coordinating timing of the bowel purge and procedure.

Most patients with lower GI bleeding can be admitted to internal medicine or gastroenterology services rather than to the general surgery services because these patients rarely require emergency surgical intervention, and given their elderly age, they usually require management of comorbid diseases by an internist. Patients should be admitted to an intensive care unit (ICU) or monitored intermediate care unit. Patients should have automatic blood pressure monitoring every 5 minutes if unstable and hourly if stable. Each patient should receive cardiac rhythm monitoring to observe for arrhythmias and to follow the heart rate as a sign of continued or recurrent bleeding. Laboratory-determined hematocrits (not finger-stick hematocrits, which are less reliable) should be obtained every 4 to 6 hours until the patient has a stable hematocrit. In cases of active bleeding, an indwelling bladder catheter should be placed to help monitor fluid status. Swan-Ganz catheter monitoring is unnecessary except for patients with a history of congestive heart failure or unstable cardiac disease. Patients older than age 60 or with risk factors for coronary artery disease should also have serial electrocardiograms and cardiac enzyme evaluation to determine whether there is any cardiac ischemia.

Endoscopy of any sort should be done only when it can be performed safely and when the information may influence patient care. Patients should be medically resuscitated with fluids and transfusions before endoscopy. Ideally, patients should be hemodynamically stable, with a heart rate of less than 100 beats/min and systolic blood pressure greater than 100 mm Hg. Hematocrit, especially in elderly patients, ideally should be greater than 28%. Severe thrombocytopenia (platelet count <50,000/mm³) should be corrected with transfusions before emergency endoscopy, and prolonged prothrombin time (>15 seconds) should be corrected with fresh frozen plasma. Performance of endoscopy in the middle of the night should be avoided unless well-trained endoscopy nurses, appropriate endoscopy equipment, and surgical backup are available.

Early Predictors of Severity in Acute Lower Gastrointestinal Bleeding

Early predictors (within 4 hours of admission) of severity for continued or recurrent bleeding after 24 hours of hospitalization include heart rate greater than 100 beats/min, systolic blood pressure less than 115 mm Hg, syncope, nontender abdominal examination, observed rectal bleeding during the first 4 hours of hospital evaluation, aspirin ingestion, and the presence of more than two comorbid conditions (Box 14.1).^6,⁷ This prediction model has been prospectively validated; the low-risk group had 0% rebleeding, the moderate-risk group had 45% rebleeding, and the high-risk group had 77% risk of rebleeding.⁷ It is possible that factors such as these can be used to help triage patients to the appropriate level of care, such as ICU, hospital ward, or outpatient evaluation and urgent versus elective endoscopic evaluation.

Mortality in Severe Lower Gastrointestinal Bleeding

A large U.S. database study comprising 227,000 patients with discharge diagnoses of lower GI bleed in 2002 reported an overall mortality rate from lower GI bleeding of 3.9%.⁸ Multivariate analysis found that independent predictors of in-hospital mortality were age (>70 years), intestinal ischemia, presence of two or more comorbid illnesses, bleeding while hospitalized for a separate process, coagulopathies, hypovolemia, transfusion of packed red blood cells, and male gender. Colorectal polyps and hemorrhoids were associated with a lower mortality risk. Patients who develop severe lower GI bleeding while hospitalized for other lesions have a much higher mortality rate than patients admitted with lower GI bleeding. In a large Kaiser Permanente San Diego retrospective study, the in-hospital mortality rate for patients with lower GI bleeding who began as outpatients was 2.4% compared with 23% for patients with in-hospital lower GI bleeding (P < .001).¹

Diagnostic Options

Most patients undergo initial evaluation with colonoscopy after bowel preparation, although in selected cases flexible sigmoidoscopy without bowel preparation or with enema preparation may be performed. Other diagnostic tests may be used in selected cases or when colonoscopy is unsuccessful.

Anoscopy

Anoscopy can be useful if actively bleeding hemorrhoids are suspected. However, nearly every patient requires additional visualization of the more proximal colon using colonoscopy or possibly sigmoidoscopy.

Flexible Sigmoidoscopy

Occasionally, flexible sigmoidoscopy may be performed to evaluate the left side of the colon quickly for any bleeding site stigmata rather than waiting for a full colonoscopy bowel preparation, and this results in a diagnosis in approximately 9% of cases.⁹ Flexible sigmoidoscopy may be especially useful in patients with strongly suspected diverticular bleeding or ischemic colitis.

Barium Enema

There is no role for emergency barium enema in a patient with severe lower GI bleeding. This test is rarely diagnostic because it cannot show vascular lesions and may be misleading if only diverticula are present. It also fails to detect 50% of polyps greater than 10 mm in size.¹⁰ Subsequent colonoscopy is needed for any suspicious lesions seen on barium enema, and no therapy can be performed.

Nuclear Medicine Scintigraphy

Nuclear medicine scintigraphy involves injecting a radiolabeled substance in the patient’s bloodstream and then performing serial scintigraphy to detect focal collections of radiolabeled material. It has been reported to detect bleeding at a rate of 0.1 mL/min.¹¹ The overall positive diagnostic rate is approximately 45%, with a 78% accuracy in the localization of the true bleeding site.¹² The most common false-positive result occurs when there is rapid transit of luminal blood such that labeled blood is detected in the colon, although it originated in the upper GI tract.

Angiography

Angiography is positive when the arterial bleeding rate is at least 0.5 mL/min.¹³ The diagnostic yield depends on patient selection, timing of the procedure, and the skill of the angiographer, with positive yields in 12% to 69% of cases. An advantage of angiography is that embolization can be performed to control some bleeding lesions. There is also a 3% rate of major complications, however, including hematoma formation, femoral artery thrombosis, contrast dye reactions, renal failure, and transient ischemic attacks.¹⁴

Computed Tomography Colonography

Computed tomography (CT) visualization of the colon is increasingly used to evaluate the colon for polyps and masses and may be of some benefit in lower GI bleeding. Faster scanners allow CT angiography, CT colonography, and CT evaluation of the small bowel to be performed. Use of CT potentially could allow diagnosis of mass lesions and vascular lesions, which would be an advantage compared with other radiologic imaging studies. One study from France reported that CT accurately diagnosed 17 of 19 lower GI bleeding sites, including diverticula, tumors, angiomas, and varices.¹⁵

Colonoscopy

Urgent colonoscopy using a rapid sulfate purge has been shown to be safe, to provide important diagnostic information, and sometimes to allow therapeutic intervention.¹⁶ Patients usually ingest 4 to 8 L of polyethylene glycol either orally or via NG tube over 3 to 5 hours until the rectal effluent is clear of stool, blood, and clots. Metoclopramide may be given intravenously before the purge and repeated every 3 to 4 hours to facilitate gastric emptying and reduce nausea.

Most “urgent” colonoscopy for lower GI bleeds is performed 6 to 36 hours after the patient is admitted to the hospital. Because most bleeding stops spontaneously, cases are often performed more electively the day after initial hospitalization to allow the patient to receive blood transfusions and to have the bowel preparation during the 1st day of hospitalization.

The overall diagnostic yield of a presumed or definite etiology using colonoscopy in lower GI bleeding ranges from 48% to 90%, with an average of 68%, based on a review of 13 studies.¹² The problem with interpreting these data is that it is often impossible to determine a definite diagnosis of the cause of the bleeding, unless bleeding stigmata are identified such as active bleeding, a visible vessel, an adherent clot, mucosal friability or ulceration, or the presence of fresh blood limited to a specific part of the colon. A presumptive diagnosis often is made, especially in the case of diverticulosis, in which no blood is seen but there is a potential bleeding site present.

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