Meckel’s Diverticulum

Meckel's diverticulum is a true congenital diverticulum of the small intestine that contains all three intestinal wall layers: mucosa, submucosa, and muscularis. This developmental anomaly represents a remnant of the vitelline (omphalomesenteric) duct that failed to obliterate during embryonic development.

Pathophysiology

The persistent vitelline duct creates an outpouching of the ileum that frequently contains ectopic gastric mucosa. This ectopic tissue produces acid within the small intestine - a problematic situation since this occurs distal to the duodenum, where pancreatic bicarbonate normally neutralizes stomach acid. Without this protective buffering mechanism, the unchecked acid production leads to painless ulceration and bleeding, which is the hallmark presentation of symptomatic Meckel's diverticulum.

The bleeding is painless because the ileum is innervated by visceral sensory nerves, which are poorly localized and don't transmit pain from mucosal ulceration very well. Unlike somatic pain (e.g. from anal fissures or appendicitis), visceral pain from mucosal ulceration is often silent or vague.

Rule of 2s

This condition is easily remembered through the classic "Rule of 2s":

• Prevalence: Occurs in approximately 2% of the population
• Location: Found approximately 2 feet from the ileocecal valve
• Size: Typically 2 inches long
• Age: Commonly presents before age 2 years
• Ectopic tissue: 2 types are most common-gastric and pancreatic mucosa
• Gender: 2x more common in males

Clinical Presentation

The majority of patients with Meckel's diverticulum remain asymptomatic throughout their lives. However, when symptoms do occur, they typically include:

Most Common Presentation

• Painless lower gastrointestinal bleeding (presenting as either melena or hematochezia)
  • Iron-deficiency anemia (often the only initial finding)

Other Possible Complications

• Intussusception (telescoping of bowel segments)
  • Meckel’s diverticulum acts as a lead point
• Volvulus (twisting of the bowel)
  • Meckel’s can be attached to the umbilicus or mesentery via a fibrous band (from the vitelline duct remnant). The bowel can twist around this fibrous band, especially during peristalsis or movement.
• Bowel obstruction
  • Due to conditions above
• Diverticulitis (inflammation that can mimic appendicitis)
  • The diverticulum can become infected or inflamed, especially if food or fecal matter gets trapped.

Keep note:

Remember that appendicitis typically causes significant pain, while Meckel's diverticulum bleeding is characteristically painless-unless complicated by diverticulitis.

Diagnosis

The diagnostic test of choice is a technetium-99m pertechnetate scan (commonly called a "Meckel scan"). This nuclear medicine study works because the radioisotope has an affinity for gastric mucosa, allowing visualization of ectopic gastric tissue within the diverticulum.

In complicated cases or when the Meckel scan is inconclusive, additional imaging studies such as CT or MRI may be necessary to establish the diagnosis.

Management Approach

Symptomatic Patients

Surgical resection is the standard treatment, which may involve either:

• Simple diverticulectomy
• Segmental ileal resection (depending on the clinical situation)

Asymptomatic Patients

Management of incidentally discovered Meckel's diverticulum remains somewhat controversial. Many experts recommend leaving asymptomatic diverticula in place unless the patient is at high risk for future complications.

• Think Meckel's diverticulum in any young child presenting with painless rectal bleeding
• The technetium-99m scan is your diagnostic study of choice
• Don't confuse with appendicitis-the absence of pain (unless diverticulitis is present) is a key differentiating feature