Meckel diverticulum

A Meckel diverticulum is the most common congenital anomaly of the gastrointestinal (GI) tract and is caused by an incomplete obliteration of the vitelline duct. It is commonly approx. 5 cm (2 inches) long and located 60 cm (2 feet) proximal to the ileocecal valve. The diverticulum may contain native ileal mucosa or heterotopic (most commonly gastric) mucosa. Meckel diverticula are often asymptomatic and detected incidentally on imaging or during abdominal surgery. A symptomatic Meckel diverticulum usually causes painless lower GI bleeding in children < 2 years. Patients may also present with complications from a Meckel diverticulum including diverticulitis, bowel obstruction, and, rarely, peritonitis due to Meckel diverticulum perforation. Meckel diverticulum should be considered in patients with lower GI bleeding and inconclusive findings on initial workup. Diagnostic studies for Meckel diverticulum include Meckel scan, endoscopy, and laparoscopy. A symptomatic Meckel diverticulum is treated with surgical resection. For an asymptomatic Meckel diverticulum detected incidentally during abdominal surgery, resection is indicated in children and may be considered in adults. An asymptomatic Meckel diverticulum detected incidentally on imaging does not require treatment.

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

Epidemiological data refers to the US, unless otherwise specified.

Embryology

• 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. ^[2]
• Incomplete obliteration of the omphalomesenteric duct → persistence of the proximal (intestinal) segment of the duct → Meckel diverticulum

Meckel diverticulum

• True diverticulum
• Located ∼ 60 cm (2 feet) proximal to the ileocecal valve (on the antimesenteric side of the ileum) ^[3]
• Commonly ≤ 5 cm (2 inches) long
• May contain 2 types of mucosa ^[4]
  • Native ileal mucosa
  • Ectopic mucosa
    • Most common: acid-producing gastric mucosa (∼ 60%) ^[2]
    • Other types include pancreatic, colonic, and duodenal mucosa.
• Presence of ectopic gastric mucosa or pancreatic tissue → acid or enzyme secretion within the diverticulum → ileal ulceration → bleeding
• Blood supply: vitelline artery ^[5]

The rule of two's describes common features of Meckel diverticula: 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): often detected incidentally on imaging or during abdominal surgery
• Symptomatic ^[1][6]
  • Painless lower GI bleeding (most common presentation), e.g.:
    • Hematochezia
    • Melena
  • Symptoms of complications, e.g.:
    • Symptoms of diverticulitis (e.g., abdominal pain)
    • Symptoms of intussusception (e.g., currant jelly stools)
    • Symptoms of GI perforation
    • Symptoms of bowel obstruction
    • Symptoms of anemia

Approach ^[1][6][7]

• Initial diagnostics for symptomatic patients are based on clinical presentation.
  • See “Initial evaluation of GI bleeding.”
  • See “Approach to acute abdomen.”
• Consider imaging studies (e.g., CT, US) to narrow the differential diagnosis or assess for suspected complications (e.g., brisk bleeding, bowel obstruction, bowel perforation).
• Perform a Meckel scan in patients (particularly children) with a suspected Meckel diverticulum.
• Consider endoscopy or laparoscopy if diagnosis remains uncertain.

Meckel scan ^[7][8]

• Description: a noninvasive nuclear medicine imaging technique using technetium-99m pertechnetate, which is preferentially absorbed by the gastric mucosa
• Indications
  • Suspected Meckel diverticulum without active bleeding
  • Occult bleeding with unclear etiology
• Findings: visualization of ectopic gastric mucosa lining the diverticulum ^[8]

Other imaging studies ^[1][7][9]

Routine imaging has low sensitivity and specificity for Meckel diverticula and is typically used to assess complications.

• Ultrasound abdomen
  • Commonly used initial imaging modality in children
  • May show intussusception or inflamed diverticula
• CT or MRI abdomen with IV contrast
  • May rule out differential diagnoses (e.g., appendicitis)
  • May show signs of complications (e.g., diverticulitis, bowel perforation, bowel obstruction)
  • Oral contrast improves sensitivity ^[1]
• CT angiography
  • Used to localize the source of a GI bleed
  • Patent vitelline artery is pathognomonic for Meckel diverticulum ^[7]

Endoscopy ^[7]

• Double-balloon enteroscopy: an enteroscopic technique to visualize the entire small intestine
  • A long endoscope is advanced into the small intestine through the mouth or rectum.
  • Sequentially inflating and deflating two balloons advances the scope into the intestine by pleating the bowel over the scope.
• Capsule endoscopy: allows for direct visualization of the diverticulum, but may fail to detect the diverticulum if the capsule passes the diverticular opening without recording it

• Differential diagnoses of GI bleeding ^[6]
  • Common causes of GI bleeding
  • Causes of lower GI bleeding in children
  • Mimics of GI bleeding (e.g., red dye ingestion, swallowed blood)
• Differential diagnoses of acute abdominal pain
• Differential diagnoses of bowel obstruction

The differential diagnoses listed here are not exhaustive.

All symptomatic diverticula require surgery. Managing asymptomatic diverticula is more nuanced and involves weighing the risk of future complications against surgical risks.

Management of symptomatic diverticula ^[6]

• Stabilize hemodynamically unstable patients using the ABCDE approach, e.g.:
  • Initiate immediate hemodynamic support.
  • Manage hemorrhagic shock.
• Begin management of acute symptoms:
  • See “Initial management of overt GI bleeding.”
  • See “Approach to management of acute abdomen.”
• If a Meckel diverticulum is confirmed or likely, consult surgery for operative management.
• In consultation with surgery, determine disposition:
  • Admit all patients with ongoing GI bleeding or urgent need for surgery.
  • Consider ICU admission for hemodynamic instability or massive GI bleeding.
  • Consider discharging patients with minor resolved bleeding and outpatient follow up.

Management of asymptomatic diverticula ^[8][10][11]

• Detected on imaging: no treatment necessary
• Incidental finding during unrelated surgery
  • Children: resection typically indicated
  • Adults: individualized decision

Surgery ^[8][11]

• Indications
  • Symptomatic diverticula
  • Selected asymptomatic diverticula incidentally found during unrelated surgery ^[8][10]
• Procedures (open or laparoscopic)
  • Diverticulectomy
  • Bowel resection

• GI 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
• 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.