Meckel Diverticulum - Clinical Tree

Wilhelm Fabricius Hildanus, a German surgeon, first described the presence of a small bowel diverticulum in 1598. However, the diverticulum is named for Johann Meckel, a German anatomist, who further described the anatomy and embryology in 1809. Meckel diverticulum is a remnant of the embryologic vitelline (omphalomesenteric) duct that connects the fetal gut with the yolk sac and normally involutes between the 5th and 7th weeks of gestation. Failure of duct regression results in a variety of abnormalities arising from persistence of the remnant ( Fig. 40.1 ). The most common anomaly (90%) is the classic Meckel diverticulum. It is a true diverticulum, consisting of all normal layers of the bowel wall. Clinical symptoms and complications can arise from small bowel obstruction, bleeding, inflammation, umbilical abnormalities, or neoplasia.

Epidemiology

The true incidence of Meckel diverticulum is unknown, because most patients are asymptomatic. Although the incidence is typically estimated at approximately 2%, a systematic review of autopsy studies found an incidence of 1.2%. The incidence may be increased in patients with major anomalies of the umbilicus, alimentary tract, nervous system, or cardiovascular system. An estimated 4% of patients with Meckel diverticulum will become symptomatic, and the risk of developing symptoms decreases with age. A report based on data from the Pediatric Health Information System database found that 53% of Meckel diverticulectomies are performed before 4 years of age, with a male-to-female ratio of 2.3:1 overall and 3:1 in symptomatic patients. The commonly cited “rule of 2s” regarding the diverticulum is: occurs in 2% of the population, has a 2:1 male-to-female ratio, usually discovered by 2 years of age, located 2 feet (60 cm) from the ileocecal valve, commonly 2 cm in diameter and 2 inches (5 cm) long, and can contain two types of heterotopic mucosa. Gastric is the most common type of heterotopic mucosa, followed by pancreatic ( Fig. 40.2 ). More rarely, it may contain duodenal, colonic, or endometrial tissue.

Fig. 40.2, This laparoscopic view shows a long Meckel diverticulum emanating from the antimesenteric border of the ileum. This is a true diverticulum and contains ectopic mucosa at the tip of the diverticulum (arrow).

Clinical Presentation

A variety of symptoms can develop depending on the configuration of the remnant structure and the presence of ectopic mucosa. The three most common presentations in children are intestinal bleeding (30–56%), intestinal obstruction (14–42%), and diverticular inflammation (6–14%). Other less common signs include a cystic abdominal mass and a newborn with an umbilical fistula resulting from a patent vitelline duct ( Fig. 40.3 ). A Littré hernia refers to a Meckel diverticulum found incarcerated in a hernia, which may be located at the inguinal, femoral, umbilical, or Spigelian sites. In adults, especially the elderly, neoplasia can develop within the Meckel diverticulum. Carcinoid is the most common tumor, but other malignancies include adenocarcinoma, leiomyosarcoma, gastrointestinal stromal tumors, and lymphoma. Neonatal presentation of a Meckel diverticulum is uncommon and typically is due to perforation or obstruction.

Fig. 40.3, This neonate was born with an obvious patent omphalomesenteric duct. (A) Meconium was seen to emanate from the stoma. (B) A circumumbilical incision was made, and the duct (arrow) was dissected to its connection with the ileum. (C) The duct was amputated from the ileum and the umbilical incision closed. The patient recovered uneventfully and has not developed any further problems.

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