Meckel Diverticulum
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Direct answer
Meckel diverticulum is a true congenital diverticulum of the ileum, a remnant of the vitellointestinal duct on the antimesenteric border. The rule of twos describes it as about two per cent of people, two inches long, within two feet of the ileocaecal valve and often symptomatic before two years of age. It usually presents as painless rectal bleeding in a toddler, and the technetium-99m pertechnetate scan is the classic investigation.
What you must remember
- Rule of twos: about 2 per cent prevalence, about 2 inches (5 cm) long, within 2 feet of the ileocaecal valve, and often symptomatic before 2 years of age.
- True diverticulum: contains all layers of the ileal wall, which separates it from acquired false diverticula that protrude through the muscle layer.
- Ectopic tissue: gastric mucosa is the commonest ectopic tissue, followed by pancreatic tissue, and ectopic gastric mucosa can ulcerate and bleed.
- Classic presentation: painless rectal bleeding in a toddler, often with maroon or fresh blood while the child otherwise looks well.
- Complications: bleeding, obstruction, intussusception and perforation, with the diverticulum acting as a lead point for intussusception.
- Investigation: technetium-99m pertechnetate scan, which is taken up by ectopic gastric mucosa, while a negative scan does not fully exclude the diagnosis.
- Treatment: surgical resection for symptomatic disease, usually a wedge excision when the base is narrow and segmental ileal resection when the base is wide.
Confirming the diagnosis and choosing the operation
Meckel diverticulum is often suspected only after a bleed, because the child looks well between episodes. The steps below run from history to operation.
- Take the history: painless, fresh or maroon blood per rectum in a young child who looks well between episodes is the key clue.
- Exclude other causes: if bleeding persists, colonoscopy or upper endoscopy looks for polyps, colitis and ulcers, which also cause painless bleeding.
- Perform the scan: a technetium-99m pertechnetate scan is taken up by ectopic gastric mucosa in the right lower abdomen, and it is a useful first test in children.
- Assess complications: check for intussusception, obstruction or perforation, because a complicated diverticulum changes the urgency of surgery.
- Excise the diverticulum: a wedge or segmental resection, with the ileum resected if the base is wide, is done when the diverticulum is symptomatic.
- Review pathology: histology confirms the ectopic tissue and rules out other pathology, such as an ulcer or tumour.
Where the exam tries to catch you
Meckel diverticulum questions reward recall of the rule of twos and the scan.
- Trap: assuming a negative technetium scan rules out Meckel diverticulum. Correct: the scan misses diverticula that lack ectopic gastric mucosa, so a negative result does not exclude the diagnosis.
- Trap: calling the diverticulum an acquired false diverticulum. Correct: Meckel diverticulum is a true congenital diverticulum containing all layers of the ileal wall.
- Trap: treating painless bleeding in a toddler with repeated stool tests and antibiotics. Correct: the picture is a diagnostic clue for Meckel diverticulum, so the child needs imaging and surgical review.
Frequently asked questions
What is the rule of two for Meckel diverticulum?
The rule of two says Meckel diverticulum occurs in about 2 per cent of people, is about 2 inches long, sits within about 2 feet of the ileocaecal valve and often presents before 2 years of age. It also contains two common types of ectopic tissue, gastric and pancreatic. It is a teaching aid, and real presentations vary.
Which ectopic tissue is most common in Meckel diverticulum?
Gastric mucosa is the most common ectopic tissue in Meckel diverticulum, followed by pancreatic tissue. Ectopic gastric mucosa secretes acid, which can ulcerate the adjacent ileal wall and cause painless bleeding.
Why is Meckel diverticulum called a true diverticulum?
Meckel diverticulum is called a true diverticulum because it contains all layers of the ileal wall, including mucosa, submucosa, muscularis and serosa. Acquired false diverticula, by contrast, protrude through the muscle layer.
Which operation is performed for symptomatic Meckel diverticulum?
Symptomatic Meckel diverticulum is treated by surgical resection, usually a wedge excision when the base is narrow and a segmental ileal resection when the base is wide. The choice depends on the width of the base and the surgeon's findings at operation.
Why can a Meckel diverticulum cause intussusception?
A Meckel diverticulum can act as a lead point, around which the ileum telescopes into the bowel to cause intussusception. This is a recognised complication, particularly in older children and adults.