Review Question - QID 106478

This patient has Meckel's diverticulum, which is caused by incomplete closure of the vitelline duct, also known as the omphalomesenteric duct or yolk stalk, which typically closes by around 7 weeks gestation.

Meckel's diverticulum is the most common congenital GI abnormality that forms a blind outpouching in the ileum. It is often associated with the rules of 2: presents before 2 years of age, occurs in 2% of population, located 2 feet proximal to the ileocecal valve, occurs twice as frequently in males as females, is symptomatic in only 2% of patients, and is generally 2 inches in length. Meckel's is a true diverticulum and often contains ectopic gastric tissue, but may also contain ectopic pancreatic tissue as well, and may present with GI bleeding or small bowel obstruction.

Martin et al. discuss the common presentation, differential diagnosis, and treatment of Meckel's diverticulum. As it is so common, they propose that it should be considered in patients with abdominal pain, gastrointestinal bleeding, and nausea and vomiting. Complications of Meckel's diverticulum include bowel obstruction, intussusception, and perforation. Technetium-99m pertechnetate scan is a diagnostic modality which locates ectopic gastric tissue and is commonly used to diagnose Meckel's diverticulum. However, it may miss those patients without ectopic gastric tissue.

Sun et al. describe two cases in which sonography was used to diagnose intestinal obstruction due to a persistent vitelline duct. They describe the multiple different possible outcomes of the vitelline duct, including a Meckel's diverticulum, a patent duct, a sinus, a vitelline duct cyst, an umbilical mucosal polyp, and a fibrous remnant. They propose that high frequency ultrasound can be used to diagnose intestinal obstruction due to the fibrous band remnants of the omphalomesenteric duct. They also discuss that Meckel's diverticulum can be diagnosed with ultrasound.

Illustration A is a gross image of a Meckel's diverticulum, seen here as an out-pouching from the GI tract. Remember, it is typically 2 inches in length and is a true diverticulum (contains all layers of the mucosal wall). Illustration B is a histological view of a biopsy of Meckel's diverticulum containing ectopic gastric tissue. If the ectopic gastric tissue is active and secretory, then it can lead to GI bleeding and perforation.

Incorrect Answers:
Answer 1: Obstruction of the appendix with fecalith is a common cause of appendicitis, which would present with peri-umblical pain that can then migrate to McBurney's point.

Answer 3: A midgut volvulus can have a similar presentation of intermittent abdominal pain with GI bleeding, but would not have the same findings on imaging or gross pathology.

Answer 4: Pyloric stenosis would tend to present with projectile vomiting and an olive shaped mass in the right upper quadrant.

Answer 5: Ingestion of contaminated water can lead to infections such as Giardia, which can lead to chronic fatty stools.