Meckel Diverticulum

Basics

DESCRIPTION

  • Meckel diverticulum (MD) is the most common congenital abnormality of the gastrointestinal (GI) tract.
  • Derives from remnants of the omphalomesenteric duct
  • The most common clinical presentation of MD is painless rectal bleeding.
  • Classically characterized by “Rule of 2’s”
    • Present in approximately 2% of the population
    • Male-to-female ratio 2:1
    • Within 2 feet of the ileocecal valve
    • Can be up to 2 inches in length
    • Symptoms usually present by 2 years of age.

EPIDEMIOLOGY

  • MD as an anomaly occurs in ~2% of the population, but only ~4% of patients with MD develop symptoms over their lifetime.
  • MD is more common in patients with other malformations including anorectal atresia, esophageal atresia, omphalocele, and cardiac abnormalities.
  • MD is considered to be more common in males, with a male-to-female ratio of 2:1.
  • Males also more likely to have symptomatic diverticula.

PATHOPHYSIOLOGY

  • Diverticula with ectopic tissue are more likely to be symptomatic.
  • Ectopic tissue in MD is often of gastric origin; can also be comprised of pancreatic, duodenal, or colonic tissue
  • Bleeding occurs when gastric mucosa is present, resulting in peptic ulcerations of the small bowel downstream from the diverticulum (90% of cases).
  • Alkaline secretions from ectopic pancreatic tissue can also cause ulcerations with bleeding.
  • Obstruction can occur when the diverticulum acts as a lead point for intussusception, when the diverticulum becomes inflamed with subsequent lumen narrowing, or when the diverticulum induces a volvulus.

ETIOLOGY

  • True diverticulum (contains all three layers of the bowel wall)
  • Originates from the antimesenteric border of the bowel in the region of the terminal ileum and proximal to the ileocecal valve
  • Remnant of the omphalomesenteric (vitelline) duct which fails to involute completely during the 5th to 6th week of gestation as the placenta replaces the yolk sac as the source of fetal nutrition
  • MD accounts for 90% of the vitelline duct anomalies. Other anomalies include the following:
    • Omphalomesenteric fistula
    • Omphalomesenteric cyst
    • Fibrous band

ASSOCIATED-CONDITIONS

  • MD has also been associated with several other congenital anomalies that include the following:
    • Anorectal atresia (affects 11% of patients with MD)
    • Esophageal atresia (12%)
    • Minor omphalocele (25%)
    • Cardiac malformations
    • Exophthalmos
    • Cleft palate
    • Annular pancreas
    • Some central nervous system malformations
  • Malignancies have also been reported in association with MD.
    • Can be present within the diverticulum and can cause obstructive symptoms or can be found incidentally
    • Sarcomas are the most common malignancy associated with MD, followed by carcinoids and adenocarcinomas.

There's more to see -- the rest of this topic is available only to subscribers.