Gastroenterology · Congenital Anomalies
The facts most likely to be tested
Meckel diverticulum results from the failure of the vitelline duct (omphalomesenteric duct) to obliterate during fetal development.
The classic presentation is painless lower gastrointestinal bleeding in a child younger than two years old.
The diverticulum contains ectopic gastric mucosa, which secretes acid and causes ulceration of the adjacent small bowel mucosa.
The Rule of 2s dictates that it occurs in 2% of the population, is 2 inches long, is located 2 feet from the ileocecal valve, and often presents before age 2.
The diagnostic test of choice is a Technetium-99m pertechnetate scan (Meckel scan), which identifies the ectopic gastric mucosa.
Complications include intussusception, small bowel obstruction (via fibrous band), and diverticulitis that mimics acute appendicitis.
Symptomatic Meckel diverticulum requires surgical resection of the diverticulum and the involved segment of the ileum.
Vignette unlocked
A 18-month-old male is brought to the emergency department by his parents due to two episodes of maroon-colored stools. The parents report that the child has been otherwise healthy and has had no fever, vomiting, or abdominal pain. Physical examination reveals a soft, non-tender abdomen with no palpable masses. Laboratory studies show a hemoglobin of 9.2 g/dL. A Technetium-99m pertechnetate scan is performed and demonstrates focal uptake in the right lower quadrant.
What is the most likely diagnosis?
Meckel diverticulum
The patient's presentation of painless hematochezia in a toddler combined with a positive Meckel scan is pathognomonic for Meckel diverticulum, which is caused by ectopic gastric mucosa.
Full handout
High yield triage
Etiology / Epidemiology
Congenital remnant of the vitelline duct; follows the Rule of 2s.
Clinical Manifestations
Painless lower GI bleeding in a child; currant jelly stool is rare but possible.
Diagnosis
Meckel scan (Technetium-99m pertechnetate) is the gold standard.
Treatment
Surgical resection is the definitive treatment for symptomatic cases.
Prognosis
Complications include intussusception, volvulus, and diverticulitis.
Full handout
Epidemiology & Etiology
The most common congenital anomaly of the GI tract, occurring in ~2% of the population. It is a true diverticulum resulting from the failure of the omphalomesenteric duct to obliterate. It is typically located within 2 feet of the ileocecal valve.
Pertinent Anatomy
Located on the antimesenteric border of the distal ileum. It may contain ectopic gastric or pancreatic tissue, which is the primary driver of clinical pathology.
Pathophysiology
Ectopic gastric mucosa secretes acid, leading to ulceration of the adjacent normal ileal mucosa. This ulceration causes painless, significant lower GI hemorrhage. Obstruction can also occur via intussusception or fibrous bands.
Clinical Manifestations
Most patients are asymptomatic. Symptomatic patients present with painless hematochezia or melena. Red flag symptoms include signs of acute abdomen or bowel obstruction. Rule of 2s: 2% prevalence, 2 feet from valve, 2 inches long, 2 types of ectopic tissue, 2 years of age (most common presentation).
Diagnosis
Meckel scan (Technetium-99m pertechnetate) detects ectopic gastric mucosa. Sensitivity is highest in children; false negatives occur in adults. Angiography may be used if the scan is negative but bleeding is active.
Treatment
Surgical resection (diverticulectomy) is indicated for symptomatic patients. Do not perform prophylactic resection in asymptomatic adults unless found incidentally during other abdominal surgery. If the diverticulum is wide-based, a segmental ileal resection may be required.
Prognosis
Excellent outcomes post-resection. Complications include diverticulitis (mimicking appendicitis), bowel obstruction, and chronic anemia from occult blood loss.
Differential Diagnosis
Intussusception: classic sausage-shaped mass
Appendicitis: RLQ pain with migration
IBD: associated with diarrhea and systemic symptoms
Hemorrhoids: bright red blood per rectum, usually painful
Polyps: usually painless but rarely cause massive hemorrhage