Meckel Diverticulum
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Direct answer
Meckel diverticulum is the vitelline (omphalomesenteric) duct remnant on the antimesenteric border of the terminal ileum, organised by the rule of twos: about 2% of people, classically 2 feet from the ileocaecal valve, 2 inches long, commonly presenting before 2 years, with 2 ectopic tissue types. It is a true diverticulum with all bowel layers, frequently lined by ectopic gastric mucosa whose acid secretion ulcerates the adjacent ileal mucosa, making painless lower gastrointestinal bleeding the commonest presentation in children. The technetium-99m pertechnetate scan, taken up by gastric mucosa, diagnoses the bleeding diverticulum. Symptomatic diverticula are treated by segmental ileal resection rather than simple diverticulectomy, because the bleeding ulcer lies in the ileum beyond the diverticulum.
What you must remember
- Rule of twos: 2% prevalence, 2 feet from the ileocaecal valve, 2 inches long, 2% (a minority) symptomatic, commonest under 2 years, 2 ectopic tissue types — gastric and pancreatic.
- Embryology: failure of obliteration of the vitellointestinal duct produces a spectrum from a complete fistula at the umbilicus to a fibrous band, cyst, or the classical diverticulum.
- Bleeding presentation: painless brick-red or maroon rectal bleeding in a toddler from an acid-induced ileal ulcer adjacent to ectopic gastric mucosa — the commonest paediatric presentation.
- Other presentations: obstruction by intussusception (diverticulum as lead point) or volvulus around a persistent band; diverticulitis mimicking appendicitis; and the Littre hernia — a Richter-type entrapment of the diverticulum, classically femoral or inguinal.
- Diagnostic scan: technetium-99m pertechnetate, concentrated by the mucus-secreting ectopic gastric mucosa, with H2-blocker preparation to enhance uptake and reduce secretion.
- Operative rule: segmental resection of ileum containing the diverticulum with the adjacent ulcer, not simple diverticulectomy, whenever bleeding or gastric mucosa is involved.
- Incidental finding: a symptomless diverticulum found during surgery for another reason may be left alone in adults, while resection is more liberally considered in children — a recognised debate answer.
Why bleeding demands more than diverticulectomy
The pathology dictates the operation. Ectopic parietal cells within the diverticulum pump acid onto the neighbouring ileal mucosa, which lacks the alkaline defences of the duodenum; the resulting peptic ulcer sits at the base of the diverticulum or just beyond it on the ileal side. A wedge diverticulectomy that trims the diverticulum but leaves the ileal ulcer behind stops the anatomical problem and continues the bleeding — the classic recurrence after inadequate surgery. Segmental resection of the involved ileum with the diverticulum and end-to-end anastomosis removes both the acid source and the ulcerated target. The same logic governs the acute obstruction case: a diverticulum that has led an intussusception may be reduced and resected with its segment, and a band-attached diverticulum is removed with its band. In the Littre hernia, the strangulated diverticulum is resected with a healthy ileal margin and the hernia repaired.
The incidental Meckel
The scenario examiners love: a 30-year-old undergoing laparoscopic appendicectomy for non-specific pain, appendix normal, and a Meckel diverticulum spotted 80 cm proximal to the valve — resect or respect? The adult incidental diverticulum with no scar, no band and no ectopic tissue is commonly left alone, since the lifetime risk of it ever becoming symptomatic is small and every resection carries anastomotic risk; in a child, or when the diverticulum is inflamed, narrow-based, band-attached or clearly diseased, resection is justified. The second scenario is the "normal appendix" moment: every surgeon who finds a macroscopically normal appendix during presumed appendicitis runs the terminal ileum — the standard teaching of examining about 100 cm — because a Meckel diverticulitis is the mirror image of appendicitis in presentation. Third, remember the umbilical variants of the same embryology: a discharging umbilical fistula, a cyst, or a fibrous band tethering ileum to the umbilicus are all vitellointestinal remnants, and the exam pairs them with Meckel diverticulum as one family.
Frequently asked questions
What is the rule of twos for Meckel diverticulum?
About 2% of people, classically 2 feet from the ileocaecal valve, 2 inches long, commonly presenting under 2 years, with 2 types of ectopic tissue — gastric and pancreatic.
Which scan diagnoses a bleeding Meckel diverticulum?
Technetium-99m pertechnetate scintigraphy, which is concentrated by ectopic gastric mucosa in the diverticulum.
Why is segmental resection preferred over diverticulectomy for bleeding?
The peptic ulcer lies in the ileal mucosa adjacent to or just beyond the diverticulum, so simple diverticulectomy can leave the bleeding ulcer behind.
What is a Littre hernia?
Herniation of a Meckel diverticulum — typically femoral or inguinal — behaving like a Richter hernia with partial-wall entrapment and risk of strangulation.
What should be done with an incidentally found Meckel diverticulum in an adult?
A healthy-looking incidental diverticulum in an adult is commonly left alone, whereas resection is favoured in children or when the diverticulum is diseased, narrow-based or band-attached.