Meckel's diverticulum

Meckel's Diverticulum

Definition

Meckel's diverticulum is a congenital pouch (diverticulum) approximately two inches in length and located at the lower (distal) end of the small intestine. It was named for Johann F. Meckel, a German anatomist who first described the structure.

Description

The diverticulum is most easily described as a blind pouch that is a remnant of the omphalomesenteric duct or yolk sac that nourished the early embryo. It contains all layers of the intestine and may have ectopic tissue present from either the pancreas or stomach.The rule of 2s is the classical description. It is located about 2 ft from the end of the small intestine, is often about 2 in in length, occurs in about 2% of the population, is twice as common in males as females, and can contain two types of ectopic tissue—stomach or pancreas. Many who have a Meckel's diverticulum never have trouble but those that do present in the first two decades of life and often in the first two years.There are three major complications that may result from the development of Meckel's diverticulum. The most common problem is inflammation or infection that mimics appendicitis. This diagnosis is defined at the time of surgery for suspected appendicitis. Bleeding caused by ectopic stomach tissue that results in a bleeding ulcer is the second most frequent problem. Bleeding may be brisk or massive. The third potential complication is obstruction due to intussusception, or a twist around a persistent connection to the abdominal wall. This problem presents as a small bowel obstruction, however, the true cause is identified at the time of surgical exploration.Meckel's diverticulum is a developmental defect that is present in about 2% of people, but does not always cause symptoms. Meckel's diverticula (plural of diverticulum) are found twice as frequently in men as in women. Complications occur three to five times more frequently in males.

Causes and symptoms

Meckel's diverticulum is not hereditary. It is a vestigial remnant of the omphalomesenteric duct, an embryonic structure that becomes the intestine. As such, there is no genetic defect or abnormality.Symptoms usually occur in children under 10 years of age. There may be bleeding from the rectum, pain and vomiting, or simply tiredness and weakness from unnoticed blood loss. It is common for a Meckel's diverticulum to be mistaken for the much more common disease appendicitis. If there is obstruction, the abdomen will distend and there will be cramping pain and vomiting.

Diagnosis

The situation may be so acute that surgery is needed on an emergency basis. This is often the case with bowel obstruction. With heavy bleeding or severe pain, whatever the cause, surgery is required. The finer points of diagnosis can be accomplished when the abdomen is open for inspection during a surgical procedure. This situation is called an acute abdomen.If there is more time (not an emergency situation), the best way to diagnose Meckel's diverticulum is with a nuclear scan. A radioactive isotope injected into the bloodstream will accumulate at sites of bleeding or in stomach tissue. If a piece of stomach tissue or a pool of blood shows up in the lower intestine, Meckel's diverticulum is indicated.

Treatment

A Meckel's diverticulum that is causing discomfort, bleeding, or obstruction must be surgically removed. This procedure is very similar to an appendectomy.

Prognosis

The outcome after surgery is usually excellent. The source of bleeding, pain, or obstruction is removed so the symptoms also disappear. A Meckel's diverticulum will not return.

Key terms

Appendectomy — The procedure to surgically remove an appendix.Appendicitis — Inflammation of the appendix.Appendix — A portion of intestine attached to the cecum.Cecum — The first part of the large bowel.Congenital — Refers to a disorder which is present at birth.Distal — Away from the point of origin.Ectopic — Tissue found in an abnormal location.Intussusception — One piece of bowel inside another, causing obstruction.Isotope — Any of two or more species of atoms of a chemical element with the same atomic number and nearly identical chemical behavior but with differing atomic mass and physical properties.Peptic ulcer — A wound in the bowel that can be caused by stomach acid or a bacterium called Helicobacter pylori.Volvulus — A twisted loop of bowel, causing obstruction.

Resources

Books

Aspinall, Richard J., and Simon T. Taylor-Robinson. Mosby's Color Atlas & Text of Gastroenterology. St. Louis: Mosby-Year Book, 2001.Cousins, Claire, and Ralph Boulton. A Color Handbook of Gastroenterology. New York: McGraw-Hill, 1999.Lipsky, Martin S., and Richard Sadovsky. Gastrointestinal Problems. Philadelphia: Lippincott Williams & Wilkins Publishers, 2000.Sanderson, Ian R., and W. Allan Walker. Development of the Gastrointestinal Tract. Hamilton, Ontario, Canada: B. C. Decker, 1999.Stringer, David A., and Paul S. Babyn. Pediatric Gastrointestinal Imaging and Intervention. 2nd ed. Hamilton, Ontario, Canada: B. C. Decker, 2000.

Periodicals

al Mahmeed, T., J. K. MacFarlane, and D. Filipenko. "Ischemic Meckel's diverticulum and acute appendicitis." Canadian Journal of Surgery 43, no. 2 (2000): 146-47.Arnio, P., and I. S. Salonen. "Abdominal disorders arising from 71 Meckel's diverticulum." Annals of Surgery and Gynecology 89, no. 4 (2000): 281-84.Heider, R., D. M. Warshauer, and K. E. Behrns. "Inverted Meckel's diverticulum as a source of chronic gastrointestinal blood loss." Surgery 128, no. 1 (2000): 107-08.Martin, J. P., P. D. Connor, and K. Charles. "Meckel's diverticulum." American Family Physician 61, no. 4 (2000): 1037-42.Nagler, J., J. L. Clarke, and S. A. Albert. "Meckel's diverticulitis in an elderly man diagnosed by computed tomography." Journal of Clinical Gastroenterology 30, no. (2000): 87-88.

Organizations

American Academy of Family Physicians. 11400 Tomahawk Creek Parkway, Leawood, KS 66211-2672. (913) 906-6000. fp@aafp.org. http://www.aafp.org/.American Academy of Pediatrics. 141 Northwest Point Boulevard, Elk Grove Village, IL 60007-1098. (847) 434-4000. Fax: (847) 434-8000. kidsdoc@aap.org. http://www.aap.org/default.htm.American College of Gastroenterology. 4900 B South 31st Street, Arlington, VA 22206. (703) 820-7400. Fax: (703) 931-4520. http://www.acg.gi.org.American College of Surgeons. 633 North St. Clair St., Chicago, IL 60611-32311. (312) 202-5000. Fax: (312) 202-5001. postmaster@facs.org. http://www.facs.org/.American Medical Association. 515 N. State Street, Chicago, IL 60610. (312) 464-5000. http://www.ama-assn.org/.

Other

American Academy of Family Physicians. http://www.aafp.org/afp/20000215/1037.html."Meckel's Diverticulum." Merck Manual. http://www.merck.com/pubs/mmanual/section19/chapter268/268d.htm.

diverticulum

[di″ver-tik´u-lum] (pl. diverti´cula) (L.) a circumscribed pouch or sac occurring normally or created by herniation of the lining mucous membrane through a defect in the muscular coat of a tubular organ. See illustration.

Intestinal diverticula. From Dorland's, 2000.ileal diverticulum Meckel's diverticulum.intestinal diverticulum a pouch or sac formed by hernial protrusion of the mucous membrane through a defect in the muscular coat of the intestine.Meckel's diverticulum an occasional sacculation or appendage of the ileum, derived from an unobliterated yolk stalk.pressure diverticulum (pulsion diverticulum) a sac or pouch formed by hernial protrusion of the mucous membrane through the muscular coat of the esophagus or colon as a result of pressure from within.traction diverticulum a localized distortion, angulation, or funnel-shaped bulging of the esophageal wall, due to adhesions resulting from an external lesion.