Write a short note on Meckel's Diverticulum.

The Concept

Meckel's diverticulum is the commonest congenital anomaly of the gastrointestinal tract. It is a 'true' diverticulum (containing all layers of the bowel wall) arising from persistence of the vitellointestinal (omphalomesenteric) duct, which normally disappears in embryonic life. It projects from the antimesenteric border of the ileum, and its importance lies in the complications caused by the ectopic tissue it may contain.

The 'rule of 2S'

Its features are famously summarised by the rule of 2s: it occurs in about 2% of the population, lies about 2 feet (60 cm) from the ileocaecal valve, is about 2 inches long, may contain 2 types of ectopic mucosa (gastric and pancreatic), commonly presents by age 2, and is about twice as common in males.

Clinical Features

Most are asymptomatic. Complications arise chiefly from ectopic gastric mucosa, which secretes acid and causes peptic ulceration of the adjacent ileum → painless rectal bleeding (a classic cause of significant lower GI bleeding in a child). It can also cause intestinal obstruction (acting as the lead point of an intussusception or via a band/volvulus), or diverticulitis that mimics acute appendicitis.

Diagnosis & Management

The key diagnostic test for a bleeding Meckel's is a Meckel's (technetium-99m pertechnetate) scan, which is taken up by the ectopic gastric mucosa and localises the diverticulum. Treatment is surgical resection of the diverticulum (with the adjacent ileum if needed); a symptomatic diverticulum is always removed, and an incidentally found one may be removed if it has features suggesting risk.

WHY It Mimics Other Diseases

Meckel's diverticulum is called a 'great mimic' because its complications reproduce commoner conditions: peptic ulceration of the ileum resembles other causes of GI bleeding, and Meckel's diverticulitis is clinically indistinguishable from acute appendicitis. A useful surgical rule follows — if the appendix is found to be normal at operation for suspected appendicitis, the surgeon should examine the terminal ileum for a Meckel's diverticulum as the true cause.

The Bottom Line

Meckel's diverticulum is therefore the commonest congenital GI anomaly (rule of 2s), important for painless bleeding from ectopic gastric mucosa, diagnosed by a technetium scan and treated by resection.

A Note on Incidental Findings

When a Meckel's diverticulum is found incidentally at surgery for another reason, the decision to remove it is individualised — a narrow-necked or palpably abnormal diverticulum, or one with a suspected band, is usually resected, whereas a broad-based, normal-feeling one in an older patient may be left, since the lifetime risk of complications falls with age.

Rule of 2s — 2% of population, 2 feet from ileocaecal valve, 2 inches long.

• Commonest congenital GI anomaly; a true diverticulum from a persistent vitellointestinal duct on the antimesenteric ileum.
• Rule of 2s: 2% of people, 2 feet from ileocaecal valve, 2 inches long, 2 ectopic mucosae (gastric & pancreatic), by age 2, 2:1 male.
• Ectopic gastric mucosa → peptic ulceration → painless rectal bleeding (in children); also obstruction, intussusception, diverticulitis (mimics appendicitis).
• Diagnose bleeding Meckel's with a technetium-99m pertechnetate (Meckel's) scan (detects gastric mucosa).
• Treat by surgical resection.