General Considerations

LGIB is defined as bleeding that occurs from a source in the colon, rectum, or anus. It accounts for about 20% of major GI bleeding and is less common and generally less severe than upper GI bleeding. There are approximately 36 hospitalizations per 100,000 adults in the United States due to lower GI bleeding. It generally occurs in older adults with a mean age between 63 and 77. Nearly 80% of lower GI bleeding stops spontaneously, similar to upper GI bleeding. The overall mortality rate of lower GI bleeding is 1.5%. Similar to upper GI bleeding, patients who begin lower GI bleeding as outpatients have a significantly lower mortality rate (3.6%) than those who develop lower GI bleeding as inpatients (23%).

Definition of Bleeding

Hematochezia is defined as bright red blood per rectum and usually implies a left colonic source, although it can be caused by a more brisk, proximal source of bleeding. Maroon stools are maroon-colored blood mixed with stool and are often associated with a right colonic source of bleeding; however, they also can result from a more brisk, proximal source of bleeding. Melena refers to black, tarry, foul-smelling stool that results from the bacterial degradation of hemoglobin over a period of at least 14 hours. It usually implies an upper GI source of bleeding although it may be associated with right colonic bleeding in cases of slow motility. Ingestion of iron, bismuth, charcoal, and licorice should be excluded since they all can turn stool black. Occult blood refers to the presence of small quantities of blood in the stool that does not change its color and can only be detected by performing a stool guaiac card test. Blood loss of at least 5–10 mL/day can be detected by stool guaiac card tests. The GI tract normally loses about 0.5–1.5 mL of blood per day, which is not usually detected by guaiac tests.

Diagnostic Approach

When patients initially present with lower GI bleeding, they should be triaged and managed based on the severity of the hemorrhage (Figure 32–1).

Patients who have minor bleeding with scant hematochezia represent 75–90% of all patients with lower GI bleeding and may be evaluated as outpatients. For patients over the age of 50, colonoscopy should be performed to evaluate the source and to screen for colon cancer. In younger patients with rectal bleeding, there is debate regarding the necessity of a colonoscopy versus flexible sigmoidoscopy. Several studies demonstrate that 10–30% of patients with rectal bleeding had proximal lesions, which would have been missed by flexible sigmoidoscopy. Other studies found that no cancers and only a very few polyps would have been missed by flexible sigmoidoscopy in patients with “outlet-type bleeding,” defined as blood seen during or after defecation on the toilet paper or in the toilet bowl without symptoms or special risk factors for colorectal neoplasia.

Physicians are unable to reliably predict based on history alone, which patients with rectal bleeding will have significant pathology. As patients grow older, it becomes cost-effective to perform a full colonoscopy. Patients in their mid-30s or older should likely be evaluated with a colonoscopy, whereas patients in their 20s with outlet-type bleeding may undergo flexible sigmoidoscopy. If no lesion is discovered to explain the hematochezia, those patients should then undergo a full colonoscopy.

Another category of patients presents with chronic intermittent bleeding that manifests as guaiac-positive stool or iron deficiency anemia, or both. Evaluation of these patients can usually occur in the outpatient setting; however, if the patients are severely anemic with cardiopulmonary symptoms or disease, inpatient admission should be considered for further monitoring, evaluation, and management. All of these patients must be evaluated with colonoscopy. About 25–41% of these patients will have abnormalities on upper endoscopy. Therefore, if no source is identified on colonoscopy or if the patient has upper gastrointestinal symptoms, an upper endoscopy should be performed. Asymptomatic patients may also harbor upper GI abnormalities, and those with iron deficiency anemia should undergo an upper endoscopy.

Other patients with lower GI bleeding include those with episodic severe bleeding and continuous active bleeding who must be evaluated in the hospital. It is important to be aware that about 10–15% of cases initially thought to represent lower GI bleeding ultimately have an upper gastrointestinal source. Clues to the presence of a possible upper GI source include hematochezia with hemodynamic instability, melena, and a history of upper GI bleeding. Placement of a nasogastric tube or obtaining a prompt upper endoscopy examination should be done to rule out an upper GI source in patients with severe lower GI bleeding.

Initial Clinical Evaluation

During the initial clinical evaluation of patients with suspected acute lower GI bleeding, resuscitation should proceed simultaneously with the placement of two large-bore peripheral catheters or a central line followed by administration of intravenous fluids (normal saline or lactated Ringer solution) or packed red blood cells (RBCs), or both.

A. Symptoms and Signs

1. History

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, 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, light-headedness, and fatigue.

2. Physical findings

The physical examination should focus on the following areas:

a. vital signs—Orthostatic hypotension implies at least a 15% loss of blood volume.

b. abdominal examination—Evaluate for tenderness, masses, liver span, and splenomegaly.

c. rectal examination—Key elements include inspection of the anus, palpation for masses, characterization of the stool color, and stool guaiac card test.

B. Laboratory Findings

Among the blood tests that should be performed are a complete blood count, prothrombin time/international normalized ratio (INR), partial thromboplastin time, electrolytes, and typing and cross-matching for blood products.

Coagulopathy and thrombocytopenia should be immediately corrected if possible. Platelets should be maintained above 50,000/mL and coagulopathy should be corrected with vitamin K or fresh frozen plasma. Vitamin K should be taken orally unless the patient has cirrhosis or biliary obstruction, in which case it should be administered subcutaneously. The full effect of vitamin K is not obtained for 12–24 hours, unlike fresh frozen plasma, which immediately reverses coagulopathy. The intravenous formulation of vitamin K reverses coagulopathy more quickly and may be used in cases of severe bleeding, however, patients should be monitored for anaphylaxis. The effects of fresh frozen plasma last about 3–5 hours and large volumes (>2–3 L) may be required to completely reverse coagulopathy, depending on the initial prothrombin time. Recombinant activated factor VII has been approved for use in patients with hemophilia A and B with factor VIII and IX inhibitors. Evidence of possible benefit in patients with cirrhosis and GI bleeding has been demonstrated, although the optimal dose is unclear and recombinant activated factor VII is very expensive.

C. Diagnostic Tests

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 GI evaluation can be performed with anoscopy, flexible sigmoidoscopy, colonoscopy, rarely barium enema, and various radiologic studies.

1. Anoscopy

Anoscopy is useful only for diagnosing bleeding sources from the anorectal junction and anal canal, including internal hemorrhoids and anal fissures. It is superior to flexible sigmoidoscopy for detecting hemorrhoids in an outpatient setting and can be performed quickly in the office or at the bedside as an adjunct to flexible sigmoidoscopy and colonoscopy.

2. Flexible sigmoidoscopy

Flexible sigmoidoscopy uses a 65-cm long sigmoidoscope that visualizes the left colon. It can be performed without sedation and only minimal preparation with enemas. However, the diagnostic yield of flexible sigmoidoscopy in acute lower GI bleeding is only 9%. The role of anoscopy and flexible sigmoidoscopy in inpatients with acute lower GI bleeding is limited, since most patients should undergo colonoscopy.

3. Colonoscopy

Colonoscopy is the test of choice in the majority of patients with acute lower GI bleeding since it can be both diagnostic and therapeutic. The diagnostic accuracy of colonoscopy in lower GI bleeding ranges from 48% to 90%, and urgent colonoscopy appears to increase diagnostic yield. This wide range in yield is partially explained by different criteria for diagnosis, as often if no active bleeding, nonbleeding visible vessel, or adherent clot is found, bleeding is attributed to a lesion if blood is present in the area. The presence of fresh blood in the terminal ileum is presumed to indicate a noncolonic source of bleeding.

The overall complication rate of colonoscopy in acute lower GI bleeding is 1.3%. Bowel preparation is safe and well-tolerated in most patients. The complication rate of colonoscopy in an unprepped colon may be higher. About 2–6% of colonoscopy preparations in acute lower GI bleeding are poor. Between 4 and 8 L of a polyethylene glycol (PEG) prep solution should be administered orally or via nasogastric tube until the effluence is clear. Antiemetics and prokinetics such as metoclopramide 10 mg should be given as needed during the preparation, especially if a rapid and large volume of a PEG prep solution is needed. In patients at risk of aspiration or fluid overload the preparation must be cautiously administered.

4. Urgent colonoscopy