Lower Gastrointestinal Bleeding

Symptoms and Signs

Link

Lower Gastrointestinal Bleeding

Kathleen E. Corey, M.D., M.P.H.

Instructor of Medicine, Harvard Medical School

Chief Resident in Medicine, Massachusetts General Hospital

Fellow in Gastroenterology, Massachusetts General Hospital

Lawrence S. Friedman, MD

Professor of Medicine, Harvard Medical School

Professor of Medicine, Tufts University School of Medicine

Chair, Department of Medicine, Newton-Wellesley Hospital

Assistant Chief of Medicine, Massachusetts General Hospital

Address correspondence to:

Lawrence S. Friedman, MD

Chair, Department of Medicine

Newton-Wellesley Hospital

2014 Washington Street

Newton, MA 02462

Tel: 617-243-5480

Fax: 617-243-6701

lfriedman@partners.org

The gastrointestinal (GI) tract extends from the esophagus to the stomach, small intestine, and colon (large intestine), ending in the rectum and anus. The small intestine consists of three portions: the duodenum, which follows the stomach, the jejunum, and finally the ileum, which connects with the colon. For practical purposes the GI tract is traditionally divided broadly into the upper and lower GI tract: the dividing line is the ligament of Trietz at the junction of the duodenum and jejunum. The upper GI tract thus consists of the esophagus, stomach, and duodenum, whereas the lower GI tract contains the jejunum, ileum, and colon, including the rectum and anus. When considering GI bleeding, the distinction between the upper and lower GI tract is important, because the presenting symptoms, causes, and treatments differ. Like upper GI bleeding, lower GI bleeding can range from large-volume, life-threatening bleeding to asymptomatic blood loss found only by laboratory evaluation.

Causes

Diverticulosis is considered the most common cause of lower GI bleeding, accounting for approximately 40% of cases. Diverticulosis is characterized by small outpouchings that develop in the colon at weak points where blood vessels enter the colonic wall. Diverticula occur most commonly in the sigmoid colon, the portion of the colon just before the rectum, but they can occur throughout the colon and rarely in the small intestine. Diverticulosis is common among Americans, presumably because of their typically low-fiber diets. Diverticular bleeding occurs in only 3-5% of patients with diverticulosis and is characterized by abrupt, painless bleeding that often stops spontaneously without the need for specific therapy. However, bleeding fails to stop in 20% of cases and recurs in another 20%.

Hemorrhoids -- dilated blood vessels that occur in the rectum -- are a frequent cause of minor rectal bleeding and occasionally can cause significant bleeding. The bleeding is characterized by bright red blood that is usually painless and often not mixed with stool.

A frequent cause of lower GI bleeding in elderly persons is ischemic colitis, a form of inflammation of the colon that can occur when blood flow to the inner lining (mucosa) of the colon is inadequate. (Figure 1) (1) Ischemic colitis most commonly occurs in older persons because they are prone to conditions that reduce blood flow. Patients present with rectal bleeding, sometimes in association with pain in the left, lower abdomen. Bleeding typically subsides spontaneously.

Angioectasias are small tangles of blood vessels in the small bowel and colon that may bleed intermittently, either slowly or massively. (Figure 2) Bleeding frequently recurs, and endoscopic treatment is usually performed to prevent future bleeding. (See below)

Rarely, colonic polyps or cancers of the small intestine and colon can present with major lower GI bleeding. (Figure 3) More commonly, the bleeding is not visible but is detected microscopically in the stool. Colonic polyps are routinely removed during colonoscopy by polypectomy to prevent the polyp from developing into a colon cancer, and polypectomy can result in bleeding within days after the procedure. Fortunately, post-polypectomy bleeding usually stops on its own, but endoscopic therapy may be required. (See below)

Patients with infectious enterocolitis (infection of the small intestine and/or colon) commonly present with abdominal pain and bloody diarrhea. The presence of fever and an elevated white blood cell count should alert the healthcare provider that the cause of bleeding is an infection, most commonly caused by bacteria such as Salmonella or Campylobacter.

Patients with Crohn’s disease or ulcerative colitis, known as the inflammatory bowel diseases, may present with lower GI bleeding and more commonly have abdominal pain and diarrhea. These diseases are characterized by ulceration and inflammation that may occur throughout the GI tract in Crohn’s disease, or are limited to the colon in ulcerative colitis.

Less common causes of lower GI bleeding include inflammation following radiation therapy for cancer (radiation proctitis or enterocolitis), a bleeding Meckel’s diverticulum (a congenital outpouching in the small intestine that may produce acid, causing a bleeding ulcer in the diverticulum), and solitary rectal ulcer (often resulting from “prolapse” or slippage of rectal mucosa).

Symptoms and Signs

Patients with lower GI bleeding can presents with melena (black, tarry stool), which usually signifies bleeding from the upper GI tract but may result from bleeding in the small intestine or proximal colon; maroon stool, when red blood mixes with stool in the colon; or bright red blood, which indicates that the bleeding is either brisk or is coming from a source in the distal colon (usually the rectum). In contrast, slow or small-volume bleeding can result in normal-appearing stool with only microscopically detectable blood.

Lower GI bleeding may result in substantial blood loss, and patients may sometimes have evidence of shock, characterized by a low blood pressure and rapid heart rate, although shock is less common with lower GI bleeding than with upper GI bleeding. Accompanying anemia (low blood count) may cause patients to appear pale and feel weak. Abdominal pain in patients with lower GI bleeding is typical of ischemic and infectious colitis.

Diagnosis and Treatment

Lower GI bleeding is often less severe than upper GI bleeding and frequently stops without specific interventions. Nevertheless, any patient with lower GI bleeding should seek medical attention.(2) Patients with large-volume bleeding should be seen urgently and may require hospital admission.

A physical examination can point toward the cause and assess the severity of bleeding. A patient’s vital signs, specifically the heart rate and blood pressure, are important diagnostic clues. Patients with large-volume bleeding may have a low blood pressure or elevated heart rate. Abdominal tenderness can point toward infectious or ischemic colitis, as can a fever. Examination of the stool via a rectal examination aids in localizing the bleeding. Black or maroon stool often indicates a bleeding source in the upper GI tract or possibly the small intestine or upper colon, whereas bright red blood, unmixed with stool, generally indicates that the sigmoid colon, rectum, or anus is the source of bleeding. (3)

Lower GI bleeding can also be associated with important laboratory findings. Anemia is common, and the degree of anemia can help determine the amount of blood lost. An elevated white blood count, generally a marker of inflammation, can point toward an infectious cause of lower GI bleeding. A low platelet count or abnormal blood clotting studies, such as the prothrombin time, suggests that the patient may have an underlying condition, such as liver cirrhosis, that predisposes to bleeding.

All patients with frank lower GI bleeding need medical evaluation. If the severity of bleeding is great, blood and fluid should be administered intravenously (through a vein). Coagulopathy (blood that clots slowly) due to disease or medications should be corrected with administration of fresh frozen plasma, vitamin K, or platelets, as necessary.

Once a patient is stable with a normal heart rate and blood pressure, a colonoscopy to look for a bleeding source in the colon is generally recommended.(4) If there is any suspicion of an upper GI source of bleeding, as in a patient with melena or one who has unstable vital signs despite resuscitation, an upper endoscopy should be performed first. However, if a lower GI source is most likely, a colonoscopy can be performed alone. A colonoscope is a flexible tube with a camera on the end that can directly visualize the inside of the GI tract and, if indicated, be used to treat a bleeding source. Both upper endoscopy and colonoscopy are done using conscious sedation, and both can be done as day procedures or while a patient is admitted to the hospital. Conscious sedation involves the use of medications that control pain and anxiety but still allow a patient to breath without the help of a ventilator. In a patient with lower GI bleeding, the scope is inserted into the rectum and advanced through the entire colon and into the end of the ileum. Before colonoscopy is performed, a patient must be “prepped,” that is, have the colon cleaned out by drinking a purgative solution containing polyethylene glycol or other medications such as phosphosoda. This “clean-out” allows the entire inner surface of the colon to be seen clearly during colonoscopy so that all potential bleeding sites can be evaluated. If active bleeding is found, several endoscopic methods, including electrocautery, injection of a drug such as epinephrine that constricts blood vessels, or placement of clips that seal the bleeding vessel, can be employed. Polyps or a mass that is found can be removed or biopsied for further evaluation.

Because colonoscopy does not visualize most of the ileum and jejunum, several other studies may be recommended when lower GI bleeding appears to be emanating from the small intestine. Push enteroscopy is a procedure similar to traditional upper endoscopy, but with a longer scope. A camera on the end of a scope is inserted into the mouth and advanced beyond the duodenum as far as possible into the jejunum, thereby allowing visualization of more of the small intestine. Because of the long duration of push enteroscopy and the discomfort that can accompany it, patients generally require more sedation and have a higher risk of complications than with standard upper endoscopy. Therefore, wireless capsule endoscopy is increasingly the preferred approach to examining the small intestine for a bleeding source. Wireless capsule endoscopy, also known as a “pill camera,” uses a camera shaped like a large vitamin that is swallowed. It is able to take two pictures per second over an eight-hour period. The patient wears a recorder and battery pack on a belt while the camera transmits pictures. These pictures are then downloaded onto a computer and reviewed to see if a bleeding site is present. The pill is disposable; it simply passes through the GI tract and out in the stool.

Although capsule endoscopy can help localize a bleeding site, it does not permit treatment of the cause of bleeding. In some cases it is not clear where the bleeding is coming from even after an upper endoscopy, colonoscopy, and capsule endoscopy; in yet other cases bleeding is so rapid that a colonoscopy cannot be completed. In such cases a nuclear scan may be performed. A nuclear scan uses technetium sulfur colloid or technetium-labeled red blood cells, infused intravenously into the patient, followed by x-rays to locate the dye, to determine where bleeding in the GI tract is coming from.(5) This test does not require sedation. This test has the advantage of being able to detect slow bleeding that may be intermittent.

Once the site of bleeding is seen on capsule endoscopy or a nuclear scan, endoscopy with a special, very long endoscope -- double-balloon enteroscope -- can advance the length of the small intestine and permit therapeutic interventions. This instrument is only available in some centers. Angiography is a more invasive technique by which a contrast dye is injected into the major blood vessels of the intestine and x-rays are taken to show where the contrast is leaking (the bleeding site). If bleeding is identified, substances to occlude (e.g., microcoils) or constrict (e.g., the drug vasopressin) the bleeding vessel and stop the bleeding are injected.

With all the available options, surgery is now rarely required for lower GI bleeding, and is reserved for heavy bleeding that persists despite endoscopic or angiographic therapy. Surgery generally involves resection of the segment of bowel that is bleeding.

Figure 1: Colon polyp (arrow) with surrounding normal colonic mucosa as seen during colonoscopy

Figure 2: Ischemic colitis as seen on colonoscopy. Note that the mucosa (lining) appears red and ulcerated (the white areas) in contrast to the normal mucosa seen in Figure 1.