Meckel diverticulum

A Meckel diverticulum is the most common congenital anomaly of the gastrointestinal tract and is caused by an incomplete obliteration of the omphalomesenteric duct. It is generally about 2 inches long and located 2 feet proximal to the ileocecal valve. It is seen in 2% of the general population and is more common in males. The mucosal lining of the diverticulum may be either native ileal mucosa or heterotopic mucosa (most commonly gastric). It is often asymptomatic and detected incidentally on imaging or abdominal surgery. The characteristic presentation of symptomatic Meckel diverticulum is painless lower gastrointestinal bleeding (hematochezia) in children < 2 years. Patients may also present with acute intestinal obstruction (intussusception or volvulus), diverticulitis, and, rarely, peritonitis due to perforation of a Meckel diverticulum. A Meckel diverticulum should be suspected when the work-up of a patient with lower gastrointestinal bleed or acute abdomen reveals no abnormalities. Sensitive and specific diagnostic tests for Meckel diverticulum include Meckel scan (99m technetium scintigraphy), CT angiography, and diagnostic laparoscopy. All symptomatic/complicated cases of Meckel diverticulum must be surgically resected. An asymptomatic Meckel diverticulum detected incidentally during abdominal surgery in a child should be resected. In adults < 50 years, only an incidentally detected Meckel diverticulum with risk factors for complications (e.g., a long, broad-based diverticulum) should be resected. An asymptomatic Meckel diverticulum incidentally detected on imaging does not require treatment.

• Prevalence: most common congenital gastrointestinal tract anomaly (∼ 2% of the population) ^[1]
• Sex: ♂ > ♀ (2:1) ^[2]
• Age: < 2 years of age ^[2]

Epidemiological data refers to the US, unless otherwise specified.

• The omphalomesenteric duct (vitelline or vitellointestinal) is a patent tubular structure connecting the yolk sac to the alimentary tract in the embryo.
• The duct is normally obliterated by the 6–7^th week of intrauterine life. ^[1]
• Incomplete obliteration of the omphalomesenteric duct → persistence of the proximal (intestinal) segment of the duct → Meckel diverticulum

• Meckel diverticulum is a true diverticulum (involves all 3 layers of the small intestine)
• Located ∼ 2 feet proximal to the ileocecal valve (on the antimesenteric side of the ileum) ^[3]
• Usually ≤ 2 inches/5 cm in size
• There may be two types of mucosal lining ^[2]
  • Native ileal mucosa
  • Ectopic mucosa
    • Most common: acid-producing gastric mucosa (∼ 60%) ^[1]
    • Other types include pancreatic, colonic, and duodenal mucosa.
• Blood supply: vitelline artery ^[4]

The rule of two's: Meckel diverticulum occurs in 2% of the population, 2% are symptomatic, mostly in children < 2 years, affects males twice as often as females, is located 2 feet proximal to the ileocecal valve, is ≤ 2 inches long, and can have 2 types of mucosal lining.

• Asymptomatic
  • Most common manifestation
  • Detected incidentally on imaging or during surgery (laparoscopy/laparotomy) performed for an unrelated condition
• Symptomatic ^[1]
  • Lower gastrointestinal bleeding (most common feature)
    • Presence of ectopic gastric mucosa or pancreatic tissue → acid or enzyme secretion within the diverticulum → ileal ulceration → bleeding
    • Can manifest as:
      • Hematochezia
      • Tarry stools
      • Currant jelly stools
  • Abdominal pain (typically in the right lower quadrant)
  • Nausea and vomiting

The initial work-up follows the same protocol as that for lower gastrointestinal bleeding and/or acute abdomen. Only the imaging tests specific to Meckel diverticulum are mentioned here.

• Imaging ^[1]
  • Indications: hemodynamically stable patients with lower gastrointestinal bleeding
    • Children < 10 years
    • Adults with no abnormalities detected on endoscopy/colonoscopy/CT scan
  • Meckel scintigraphy scan (Meckel scan): a noninvasive nuclear medicine imaging technique using radiolabelled technetium (^99mTc), which is preferentially absorbed by the gastric mucosa and can identify ectopic gastric mucosa ^[1]
  • CT angiography: may demonstrate the vitelline artery or contrast extravasation from a bleeding Meckel diverticulum
  • Other imaging tests
    • Mesenteric arteriography
    • Tagged RBC scans: useful to detect a bleeding Meckel diverticulum
• New imaging techniques
  • Double balloon enteroscopy: an enteroscopic technique to visualize the entire small bowel.
    • A long endoscope is advanced, either through the mouth or the rectum, into the small intestine
    • The sequential inflation and deflation of the two balloons help advance the scope into the intestine by pleating the bowel onto the scope.
  • Capsule endoscopy: a diagnostic procedure using a tiny wireless camera fitted inside a capsule that is swallowed by the patient to take pictures of the mucosa as it passes through the GI tract.
    • The patient swallows the encapsulated camera
    • Pictures are analyzed after the capsule is excreted 24–48 hours later.
• Diagnostic laparoscopy ^[5]
  • Meckel diverticulum may be identified on diagnostic laparoscopy performed on (hemodynamically stable) patients with acute abdomen/lower gastrointestinal bleeding and negative findings using other investigations.
  • See "Anatomy" above for features of Meckel diverticulum on laparoscopy.

• Asymptomatic Meckel diverticulum
  • Incidentally detected on imaging studies: no treatment necessary
  • Incidentally detected on laparotomy/laparoscopy
    • Children or young adults: surgical resection of all incidentally detected Meckel diverticula
    • Adults < 50 years: surgical resection only for Meckel diverticula that have a high risk of developing complications
    • Adults > 50 years: no treatment necessary
• Symptomatic or complicated Meckel diverticulum
  • Initial stabilization of the patient
  • Surgical resection of all symptomatic/complicated Meckel diverticula
• Surgical procedures
  • Segmental resection: indicated for a Meckel diverticulum that is bleeding, has a broad base, or a palpable abnormality
  • Diverticulectomy: Meckel diverticulum is resected at the base.

• Hemorrhage (most common)
• Bowel obstruction (usually affects terminal ileum) due to
  • Intussusception
  • Volvulus
  • Littré hernia: incarceration of a Meckel diverticulum inside a femoral hernia.
• Bowel perforation: peritonitis or intra-abdominal abscess
• Infection (Meckel diverticulitis): patients present with acute right lower abdominal pain, mimicking acute appendicitis or acute mesenteric lymphadenitis
• Neoplasia (rare)
  • Benign tumors (e.g., leiomyoma) are the most common.
  • Leiomyosarcomas, carcinoid tumors, lipomas, fibromas, and angiomas may also be found

We list the most important complications. The selection is not exhaustive.