Meckel's Diverticulum - Simple & Easy to Remember

What is it?

A true diverticulum (has ALL 3 layers of bowel wall: mucosa + muscularis + serosa) arising from the antimesenteric border of the ileum. It is the remnant of the vitellointestinal (vitelline) duct, which normally obliterates by the 6th week of fetal life.

True diverticulum = True to the bowel (has all layers). Contrast with a pseudodiverticulum which lacks muscularis.

The Golden Mnemonic - "Rule of 2s"

2	Meaning
2%	Occurs in 2% of the population
2 inches	About 2 inches (5 cm) long
2 feet	Located 2 feet (60 cm) proximal to the ileocaecal valve
2:1 ratio	Males affected 2x more than females
2 years	Most present before age 2 (only ~4% are ever symptomatic)
2 types	2 types of ectopic tissue - gastric mucosa & pancreatic tissue

Memory hook: "Meckel's loves the number 2 - 2%, 2 inches, 2 feet, 2:1, age 2, 2 tissues"

Gross Pathology

This is what Meckel's diverticulum looks like in a surgical/pathology specimen - a blind pouch projecting from the antimesenteric side of the ileum:

Meckel's diverticulum gross specimen showing blind pouch on antimesenteric side of small bowel

Clinical Problems - "OBI"

Letter	Problem	Mechanism
O	Obstruction	Intussusception (diverticulum = lead point) or volvulus around fibrous cord remnant
B	Bleeding	Ectopic gastric mucosa secretes acid → peptic ulcer → painless rectal bleeding (most common presentation in children)
I	Inflammation	Meckel's diverticulitis mimics acute appendicitis

Trick: The most common symptom is painless rectal bleeding (maroon stool, not bright red). This is #1 in children under 2.

Diagnosis Trick

Meckel's scan (Technetium-99m pertechnetate scan) - detects ectopic gastric mucosa. Since ~85% of symptomatic Meckel's contain gastric mucosa, this scan is the initial study of choice for bleeding.
On CT: tubular blind-ending structure from antimesenteric border of terminal ileum.

Quick Summary Card

MECKEL'S DIVERTICULUM
├── Embryology: Failed obliteration of vitelline duct (6th week)
├── Type: TRUE diverticulum (all 3 layers)
├── Location: Antimesenteric border of ILEUM
├── Rule of 2s: 2% / 2 inches / 2 feet / 2:1 / Age 2 / 2 tissues
├── Ectopic tissue: Gastric (80-85%) > Pancreatic
├── Most common symptom: Painless rectal bleeding (children)
├── Mimics: Appendicitis (when inflamed)
└── Diagnosis: Meckel's scan (Tc-99m pertechnetate)

Sources: Robbins & Cotran Pathologic Basis of Disease; Sleisenger & Fordtran's Gastrointestinal and Liver Disease - consistent with your textbook image (BD Chaurasia anatomy, AN 52.6)

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