Epidemiology

Meckel's diverticulum is the most common congenital anomaly of the gastrointestinal tract. This lesion is found in 1–2% of the general population. Of those lesions that are found incidentally, males and females are equally affected. Symptomatic Meckel's occur disproportionately in male compared to females in a ration of 2–4 : 1. Among people with a Meckel's approximately 5–6% will become symptomatic.

Embryology and anatomy

Meckel's diverticulum is one of a spectrum of congenital anomalies resulting from the incomplete regression of the omphalomesenteric duct (vitelline duct). It is a true diverticulum that involves all layers of the intestinal wall that typically occurs within 100 centimeters proximal to the ileocecal valve on the anti-mesenteric border of the small intestine. Its blood supply is derived from the right vitelline artery which subsequently becomes the superior mesenteric artery. It may have a persistent connection to the umbilicus via a fibrous cord or a patent fistula. Most often it is free and isolated. Its lining may consist entirely of intestinal mucosa, but often it has heterotopic mucosa within the diverticulum. The most common type of ectopic mucosa is gastric. Other mucosal aberrations include pancreatic and colonic tissue. The majority of symptomatic patients are found to have ectopic mucosa within the diverticulum. The Meckel's that are asymptomatic are most often lined by normal intestinal epithelium.

Clinical presentation

The vast majority of Meckel's diverticula are clinically silent. Symptomatic lesions usually present before two years of age. It is often referred to by the rule of 2's; 2% of the population, within 2 feet of the ileocecal valve, 2 inches in length, tow types of heterotopic Mucosa, and presentation before the age of two. The most common clinical presentations are: 1) lower gastro-intestinal bleeding secondary to an ulceration produced by heterotopic gastric mucosa; 2) intestinal obstruction; from internal volvulus or intussusception; 3) and local inflammation with or without perforation resembling acute appendicitis. The presentation often will mimic other disease states and can be quite difficult to detect. There also is an increased association of Meckel's diverticulum with esophageal atresia, imperforate anus, omphalocele, Crohn's disease, and small omphalocele's (Matsagas MI et al. 1995; Nicol JW et al 1994; Andreyey HJ et al 1994). There has been described a Meckel's syndrome which includes the triad of occipital encephalocele, cystic kidneys, and polydactyly of all limbs (Sugira Y et al 1996).

The gastrointestinal bleeding is painless and episodic producing hematochezia redundant and occasionally bright red blood per rectum. Not infrequently it will present with massive lower intestinal bleeding. It usually will not produce occult heme positive stool. There may be an association between the use of Non-Steroidal Anti-inflammatory drugs and bleeding from the heterotopic gastric mucosa (Maieron R et al. 1995).

The obstructive symptoms are a result of the Meckel's acting as a lead point causing an entero-entero on enterocolic intussusception which often cannot be reduced hydrostatically. The Meckel's also may remain attached to the umbilicus or the base of the mesentery via a fibrous cord, a result of incompleted involution of the vitelline structures. These attachments may act as a focal point for internal herniation of small bowel or a secondary volvulus.

The local inflammatory complications results from ectopic acid producing gastric mucosa causing significant ulcerations with possible perforation. It has been suggested that Helicobacter pylori may play a role in the ulcerogenic complications of the ectopic gastric mucosa (Hill P 1998). This has not been confirmed. Most often the patients are explored with the tentative diagnosis of acute appendicitis only to find a normal appendix. With further exploration the inflamed or perforated Meckel's identified.

Diagnosis

It requires an astute clinician to diagnose a symptomatic Meckel's diverticulum in a timely fashion. The most commonly used diagnostic modality is the technetium 99 scan which is useful in detecting heterotopic gastric mucosa. It has a sensitively of 85%, specificity of 95%, and accuracy of 90%. This study may be enhanced by the use of pentagastrin which stimulates the uptake of the pertechnetate by the gastric cells. Histamine blockers may also be administered to inhibit the secretion of the pertechnetate by the gastric cells. The use of both pentagastrin and histamine H2 receptor blockers may improve the diagnostic yield (Heyman S 1994). Technetium 99 pentechnetate SPECT scan have been proposed as a more accurate method of detecting a Meckel's diverticulum (Connolly LP et al 1998). Other diagnostic modalities include ultrasound, CT scan, upper GI barium studies, and selective angiography.

Management

Symptomatic Meckel's diverticula should be resected with primary closure of the small intestine. This may be done tangentially on the antimesenteric border with closure of the small intestine in a transverse fashion to avoid narrowing the lumen. Resection of the intestine containing the diverticulum may also be carried out with an intestinal stapling device. Care must be taken to ensure that all ectopic mucosa is resected. If the lesion is resected for bleeding the intestinal mucosa should be inspected for the presence of an ulcer which will tend to occur at the junction of the ectopic gastric mucosa and normal small bowel mucosa as well as on the mesenteric side of the ileal lumen. Any bleeding site that is identified should be oversewn. One my consider the use of frozen section to ensure the complete resection of all ectopic mucosa (Fansler RF 1996).

The treatment of asymptomatic Meckel's diverticula encountered at laparotomy remains controversial. The incidence of complications from prophylactic resection is approximately 1%. This is in comparison to the lifelong potential complication rate of 5 to 6% in all individuals with a Meckel's diverticulum. It is recommended by some that the risk to benefit ratio favors the resection of all Meckel's diverticula when found incidentally (Arnold JF et al. 1997; Cullen JJ et al 1994). This is not a widely excepted opinion. The decision for resection has to be determined on an individual basis based upon the patient's overall condition and extent of the procedure being performed. Resection is indicated in those patients in which there is palpable heterotopic mucosa within the diverticula, with the history of abdominal pain, and when there is the presence of other persistent remnants of the vitellin duct. Prophylactic removal is contraindicated in patients with omphalocele.

Conclusion

The presentation of a Meckel's diverticulum often is insidious and the diagnosis is often illusive. The long term complication rate of its treatment is in the range of 5% with the most common complication being adhesive bowel obstruction. The overall mortality for symptomatic Meckel's diverticula is approximately 5%. The mortality rate for elective resection of asymptomatic Meckel's diverticula should be 0%.

References

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