Meckel’s diverticulum represents the most common congenital abnormality of the gastrointestinal tract, affecting about two percent of the general population. This condition is defined as a small, pouch-like bulge on the wall of the small intestine that is present from birth. It is a remnant of the vitelline duct, a structure that connects the developing fetal gut to the yolk sac for nourishment during early pregnancy. While the majority of individuals with this remnant never experience symptoms, its presence carries a risk of complications that can cause severe abdominal issues.
What This Congenital Anomaly Is
Meckel’s diverticulum is classified as a true diverticulum, meaning its wall contains all the layers of the small intestine: the mucosa, submucosa, and muscularis propria. It arises when the vitelline duct (or omphalomesenteric duct) fails to completely disappear during the fifth to seventh week of fetal development. Instead of fully involuting, the proximal portion of the duct persists as a blind-ending pouch.
The diverticulum is typically located in the lower section of the small intestine, the ileum, usually situated opposite the mesenteric attachment. Medical professionals often use the “Rule of 2s” mnemonic to remember its general characteristics. This rule states that the diverticulum is most frequently found about two feet (60 to 90 cm) from the ileocecal valve, the junction between the small and large intestines.
The anomaly is often about two inches (three to six cm) long, and symptoms frequently manifest before the age of two. The rule also notes that the diverticulum can contain two types of ectopic tissue, most commonly gastric or pancreatic tissue. Ectopic tissue is normal tissue growing in an abnormal location, found in about 50% of symptomatic diverticula. Gastric tissue is the most prevalent form, found in a majority of symptomatic cases.
Common Ways Meckel’s Diverticulum Presents
Ectopic gastric mucosa within the diverticulum is the primary mechanism leading to clinical symptoms. This misplaced tissue secretes hydrochloric acid, just like the lining of the stomach. Since this acid is not intended for the small intestine, it can cause an ulcer to form in the adjacent ileal lining.
This acid-induced ulceration commonly results in painless rectal bleeding, the most frequent complication seen in children. The bleeding can be substantial, appearing as dark red, maroon, or bright red blood in the stool, and it occurs suddenly without preceding pain. In adults, the most common presentation is intestinal obstruction.
Obstruction occurs when the diverticulum or an attached fibrous band physically blocks the passage of contents through the small intestine. The diverticulum can act as a leading point for intussusception, where one segment of the bowel telescopes into another. Alternatively, the remnant can form a fixed point around which the small intestine twists, a condition called volvulus, which compromises blood flow to the affected bowel section.
The diverticulum can also become inflamed, a condition known as Meckel’s diverticulitis. This inflammation often mimics the symptoms of appendicitis, including abdominal pain and tenderness, making diagnosis difficult. Although Meckel’s diverticulum is typically wide-mouthed, inflammation can still occur and potentially lead to perforation or peritonitis.
Diagnosis and Surgical Management
Because the symptoms of a Meckel’s diverticulum can mimic many other abdominal conditions, specialized imaging is required for a definitive diagnosis. The most sensitive diagnostic tool is the Technetium-99m pertechnetate scan, often called a Meckel’s scan. This nuclear medicine test involves injecting a radioactive tracer that is specifically absorbed by the acid-secreting cells of the ectopic gastric mucosa.
A camera detects the tracer’s accumulation, which appears as a fixed, localized spot in the abdomen, confirming ectopic gastric tissue. While other imaging methods like CT scans or ultrasound may be used to assess complications such as obstruction or inflammation, they are less reliable for identifying the diverticulum itself unless it is acutely inflamed. The final management for a symptomatic Meckel’s diverticulum is surgical removal, known as a diverticulectomy.
Surgical intervention is indicated once a complication, such as bleeding, obstruction, or diverticulitis, has occurred. The procedure is typically straightforward and often performed using minimally invasive laparoscopic techniques. Removal of the diverticulum, sometimes with a small surrounding segment of the small intestine, is generally curative and resolves the potential for future complications.