- Clinical science
A Meckel diverticulum is the most common congenital anomaly of the gastrointestinal tract and is caused by an incomplete obliteration of the omphalomesenteric duct. It is generally about 2 inches long and located 2 feet proximal to the ileocecal valve. It is seen in 2% of the general population and is more common in males. The mucosal lining of the diverticulum may be either native ileal mucosa or heterotopic mucosa (most commonly gastric). It is often asymptomatic and detected incidentally on imaging or abdominal surgery. The characteristic presentation of symptomatic Meckel diverticulum is painless lower gastrointestinal bleeding (hematochezia) in children < 2 years. Patients may also present with acute intestinal obstruction (intussusception or volvulus), diverticulitis, and, rarely, peritonitis due to perforation of a Meckel diverticulum. A Meckel diverticulum should be suspected when the work-up of a patient with lower gastrointestinal bleed or acute abdomen reveals no abnormalities. Sensitive and specific diagnostic tests for Meckel diverticulum include Meckel scan (99m technetium scintigraphy), CT angiography, and diagnostic laparoscopy. All symptomatic/complicated cases of Meckel diverticulum must be surgically resected. An asymptomatic Meckel diverticulum detected incidentally during abdominal surgery in a child should be resected. In adults < 50 years, only an incidentally detected Meckel diverticulum with risk factors for complications (e.g., a long, broad-based diverticulum) should be resected. An asymptomatic Meckel diverticulum incidentally detected on imaging does not require treatment.
- The omphalomesenteric (vitelline or vitellointestinal) duct is a patent tubular structure connecting the yolk sac to the alimentary tract in the embryo.
- The duct is normally obliterated by the 6th week of intrauterine life.
- Incomplete obliteration of the omphalomesenteric duct → persistence of the proximal (intestinal) segment of the duct → Meckel diverticulum
- Meckel diverticulum is a true diverticulum.
- Located ∼ 2 feet proximal to the ileocecal valve
- Usually ≤ 2 inches in size
There may be 2 types of mucosal lining:
- Native ileal mucosa
- Heterotopic mucosa
- Blood supply: vitelline artery
The rule of two's: Meckel diverticulum occurs in 2% of the population, 2% are symptomatic, mostly in children < 2 years, affects males twice as often as females, is located 2 feet proximal to the ileocecal valve, is ≤ 2 inches long, and can have 2 types of mucosal lining.
- The initial work-up follows the same protocol as that for lower and/or . Only the imaging tests specific to Meckel diverticulum are mentioned here.
- Meckel scintigraphy scan (Meckel scan): a noninvasive nuclear medicine imaging technique using radiolabelled technetium (99mTc), which is preferentially absorbed by the gastric mucosa and can identify ectopic gastric mucosa
- CT angiography: may demonstrate the vitelline artery or even contrast extravasation from a bleeding Meckel diverticulum
Recent advances in imaging
- Double balloon enteroscopy: A long endoscope is advanced, either through the mouth or the rectum, into the small intestine. The sequential inflation and deflation of the two balloons helps advance the scope into the intestine by pleating the bowel onto the scope.
- Capsule endoscopy: The patient is asked to swallow a small, encapsulated camera, which takes multiple images of the bowel as it passes through the gastrointestinal tract.
Asymptomatic Meckel diverticulum
- Incidentally detected on imaging studies: no treatment necessary
Incidentally detected on laparotomy/laparoscopy
- Children or young adults: surgical resection of all incidentally detected Meckel diverticuli
- Adults < 50 years: surgical resection only for Meckel diverticuli that have a high risk of developing complications
- Adults > 50 years: no treatment necessary
Symptomatic or complicated Meckel diverticulum
- Initial stabilization of the patient
- Surgical resection of all symptomatic/complicated Meckel diverticuli
- Segmental resection : Indicated for a Meckel diverticulum that is bleeding, has a broad base, or a palpable abnormality
- Diverticulectomy: Meckel diverticulum is resected at the base.