Meckel’s Diverticulum

Overview

Definition

A Meckel’s diverticulum is a persistent remnant of the omphalomesenteric duct. A Meckel’s diverticulum is a true diverticulum (contains all layers of the bowel wall), arising from the antimesenteric surface of the middle-to-distal ileum.

Epidemiology

• The most common congenital gastrointestinal (GI) tract anomaly 
• Prevalence: approximately 2% of the population
• Sex: males > females (2:1)
• Most commonly presents with symptoms at 2–4 years of age
• Increased incidence in children with major malformations involving the:
  • Umbilicus
  • GI tract
  • Nervous system
  • Heart

Rule of 2(s)

• 2% of population
• 2 times more common in males
• Frequently presents by 2 years of age
• 2% develop symptoms/complications
• 2 inches long
• 2 feet from the ileocecal valve

Etiology

• Omphalomesenteric duct:
  • Connects the midgut to the yolk sac in utero
  • Normally involutes between the 5th and 6th weeks of gestation
• Omphalomesenteric duct that does not fully involute can give rise to:
  • A Meckel’s diverticulum (most common persistent remnant)
  • Omphalomesenteric cysts
  • Omphalomesenteric fistula (drain through umbilicus)
  • Fibrous bands (can cause bowel obstruction)

Pathophysiology and Clinical Presentation

Anatomy

• True diverticulum: contains all histologic layers of the intestinal tract
• Located in the middle to distal ileum (2 feet from the ileocecal valve)  
• Usually arises from the antimesenteric surface
• Mucosal lining:
  • Resembles a normal small intestine
  • But may contain ectopic (heterotopic) mucosa (12%–44%):
    • Gastric (most common)
    • Pancreatic
    • Colonic
• Blood supply: vitelline artery (a branch of the superior mesenteric artery)

Pathophysiology

• GI bleeding:
  • Occurs if a Meckel’s diverticulum contains ectopic gastric mucosa
  • Gastric mucosa secretes acid and ulceration occurs → ulceration is downstream or in the adjacent small bowel mucosa → bleeding
• Meckel’s diverticulitis:
  • Acute inflammation of a Meckel’s diverticulum (similar to appendicitis)
  • Diverticular opening becomes obstructed (fecalith, food, foreign body, tumor), leading to bacterial overgrowth and inflammation.
  • May result in ischemia and perforation in severe cases
• Small bowel obstruction (SBO) may result from several mechanisms:
  • Intussusception:
    • Part of the bowel telescopes into itself.
    • A Meckel’s diverticulum acts as a lead point.
  • Volvulus:
    • A Meckel’s diverticulum sometimes has fibrous bands connecting to the peritoneum/abdominal wall.
    • Intestines can twist around the fibrous bands.
  • Torsion: twisting of the diverticulum itself
  • Meckel’s diverticulitis: Inflammation can narrow the lumen of the adjacent small bowel.
  • Littre’s hernia: The diverticulum becomes incarcerated into a hernia.
  • Inversion: The diverticulum inverts into a bowel lumen and causes intermittent obstruction.

Clinical presentation

• Frequently clinically silent
• 25%–50% of symptomatic patients are < 10 years of age.
• In adults (especially < 40 years of age): A Meckel’s diverticulum is suspected if there is no identifiable source of GI bleeding.
• Presentation similar in children and adults: 
  • Painless lower GI bleeding (most common):
    • Acute (massive hematochezia)
    • Chronic/slow (melena; currant jelly or maroon stools in children)
  • SBO:
    • Nausea/vomiting
    • Cramping abdominal pain
    • Abdominal distention
    • In children: most commonly in the form of recurrent intussusception
  • Meckel’s diverticulitis:
    • Symptoms similar to acute appendicitis
    • With signs of peritoneal irritation if perforated
    • Abdominal tenderness is usually more midline.

Diagnosis

Tests for GI bleeding

• Radiology:
  • Meckel’s scan:
    • Used as a 1st-line test in hemodynamically stable patients and if suspicion is high (usually children)
    • Nuclear medicine scan utilizing radioactively labeled technetium that binds to gastric mucosa
    • Ectopic gastric mucosa is identified on scintigraphy.
  • Arteriography:
    • If the bleeding is brisk enough to necessitate blood transfusion
    • An anomalous branch of the superior mesenteric artery feeding the Meckel’s diverticulum can be identified.
    • Invasive test
  • Computed tomography (CT) angiography:
    • More sensitive than arteriography for less-brisk hemorrhage
    • Detects slow bleeding (0.3 mL/min)
• Endoscopy:
  • Capsule endoscopy: can visualize a normal, bleeding, inverted, and ulcerated Meckel’s diverticulum
  • Double-balloon enteroscopy:
    • Confirms diagnosis and complications by visualization
    • Enteroscope can be passed via the mouth into the small bowel, or by retrograde fashion, through the colon.
    • Requires specialized skills and longer time

Tests for SBO and diverticulitis

• CT scan:
  • Will identify SBO, inflammatory changes, perforation
  • A Meckel’s diverticulum itself is diagnosed correctly in about 50%.
• Diagnostic laparoscopy:
  • Performed if imaging studies are equivocal (difficult to distinguish an inflamed diverticulum from appendicitis on imaging)
  • Can be therapeutic as well as diagnostic

Management

Asymptomatic

• A Meckel’s diverticulum incidentally found on imaging: no treatment necessary
• A Meckel’s diverticulum found during surgery (for another condition):
  • Considerations:
    • Clinical status (higher perioperative risk in older patients)
    • Life-long risk of complications (higher in children)
    • Diverticular abnormalities or features (that increase the risk of complications)
  • Resection recommended:
    • In children 
    • In healthy (< 50 years of age) adults: if a Meckel’s diverticulum is > 2 cm long or palpable abnormalities/fibrous bands are noted
    • In patients > 50 years of age or with comorbidities: if there is a palpable abnormality (heterotopic mucosa, possible tumor, fibrous bands)
  • No resection recommended: if patient is > 50 years of age and there is no palpable abnormality
• Counseling should be provided regarding possible future symptoms.

Symptomatic

• Supportive:
  • Intravenous hydration and resuscitation
  • Blood transfusion if necessary (for GI bleeding)
  • Bowel rest, nasogastric decompression (for SBO)
  • Intravenous antibiotics (for Meckel’s diverticulitis)
• Surgery (definitive treatment):
  • Emergent if signs of sepsis, peritonitis, perforation
  • Resection of a Meckel’s diverticulum
  • Segmental small bowel resection (including a Meckel’s diverticulum):
    • To include ulcerated bleeding mucosa
    • If the adjacent small bowel is severely inflamed/ischemic

Differential Diagnosis

• Acute appendicitis: presents with abdominal pain and tenderness mostly in the right lower quadrant. A CT scan can help differentiate between a Meckel’s diverticulum and appendicitis, but not with 100% accuracy. Sometimes the definitive diagnosis is only made at surgery.
• Intussusception due to other causes: in infants and toddlers, classically presents as intermittent colicky abdominal pain with currant jelly stools. Adults and older children present with symptoms of bowel obstruction. Intussusception in young children is often idiopathic, but in adults, intussusception is frequently associated with tumors.
• Volvulus (due to malrotation): congenital condition that usually manifests in infancy, but sometimes not until adulthood. Twisting of the mesentery results in intestinal ischemia. A volvulus presents with severe abdominal pain and bloody stools in advanced cases. A volvulus requires emergent surgery.
• Colonic diverticulosis and arteriovenous (AV) malformations: most common causes of painless lower GI bleeding in older adults. Colonic diverticulosis and AV malformations can present with acute (hematochezia) or chronic slow bleeding (melena). Diagnosis is usually established by colonoscopy or angiography (in actively bleeding AV malformations).