Meckel Diverticulum

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Basics

Description

  • Meckel diverticulum (MD) is the most common congenital abnormality of the GI tract.
  • Derives from the omphalomesenteric duct remnants
  • The most common clinical presentation in children 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/female ratio of 2:1.
  • Males are 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 pancreatic, duodenal, or colonic tissue as well
  • 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 3 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–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

Commonly 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.

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Basics

Description

  • Meckel diverticulum (MD) is the most common congenital abnormality of the GI tract.
  • Derives from the omphalomesenteric duct remnants
  • The most common clinical presentation in children 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/female ratio of 2:1.
  • Males are 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 pancreatic, duodenal, or colonic tissue as well
  • 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 3 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–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

Commonly 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.

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