Meckel's diverticulum overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
A Meckel's diverticulum, a true congenital diverticulum, is a small bulge in the small intestine present at birth. It is a vestigial remnant of the omphalomesenteric duct (also called the vitelline duct), and is the most frequent malformation of the gastrointestinal tract.
Historical Perspective
Meckel's diverticulum was first described by Fabricius Hildanus in the sixteenth century. In 1809, Johann Friedrich Meckel threw light on the embryological origin of Meckel's diverticulum.
Classification
There is no established system for the classification of Meckel's diverticulum.
Pathophysiology
The vitelline duct or the omphalomesenteric duct is the connection between the midgut and the yolk sac responsible for providing nutrition to the midgut, during fetal development. The vitelline duct subsequently undergoes involution,in the period between the fifth and the sixth weeks of gestation while the intestinal loop is rapidly pulled into the abdominal cavity. Failure of duct involution may lead to persistence of the proximal portion of omphalomesenteric duct, which may be referred to as the Meckel's diverticulum. The Meckel’s diverticulum is a true diverticulum (comprising of all layers of intestinal wall i.e. mucosa, submucosa and muscularis propria). It arises from the antimesenteric border of the ileum and extends into the umbilical cord. The blood supply comes from the vitelline artery, which is a branch of the superior mesenteric artery, prone to torsion, ischemia, infarction and obstruction. The diverticulum may contain ectopic tissue due to the presence of a pluripotent cell lining, faulty association between endodermal and neural crest cells and absence of inhibitory effect of the mesoderm on the local endoderm.
Causes
Persistence of the vitelline duct due to incomplete involution leads to the formation of Meckel’s diverticula, the most common congenital abnormality of the small intestine.
Differentiating Meckel's diverticulum from Other Diseases
The common diseases responsible for lower GI bleeding that must be differentiated from Meckel's diverticulum inlcude diverticulosis, angiodysplasia, hemorrhoids, anal fissures, mesenteric Ischemia, and colorectal carcinoma. Meckel's diverticulitis is a common complication of Meckel's diverticulum in adults and must be differentiated from other causes of abdominal pain and lower gastrointestinal bleeding such as infective colitis, IBD and acute ischemic colitis.
Epidemiology and Demographics
Meckel's diverticulum is present in approximately 2% of the population, as per the "Rule of 2s". This rule applies to patients with Meckel's diverticulum and states that it affects approximately 2 percent of the population with a male-to-female ratio of 2:1. It is mostly located about two feet proximal to the ileocecal valve, is approximately two inches in length, and in majority of cases, affects age group <2yrs. In addition, the two most common types of ectopic mucosa found within the diverticulum are the gastric and pancreatic types. Increased prevalence of Meckel's diverticulum is seen in children with umbilical malformations, gastrointestinal tract, neurological and cardiovascular defects.
Risk Factors
Common risk factors in the development of Meckel's diverticulum include histologic and anatomic features such as length of diverticulum >2cm, presence of ectopic tissue, broad based diverticulum, and attachment of fibrous bands to the diverticulum. Patient age of less than 50 years and the male gender are more susceptible to the development of Meckel's diverticulum.
Screening
There is insufficient evidence to recommend routine screening for Meckel's diverticulum.
Natural History, Complications and Prognosis
Meckel's diverticulum is mostly seen in male children (mostly <2 years of age). One fourth of untreated cases of Meckel's diverticulum may develop complications such as intestinal obstruction, hemorrhage, diverticulitis, bowel ischemia, and necrosis. Hemorrhage is the most common complication in patients with Meckel's diverticulum. Bleeding in patients may be minimal, recurrent or massive and shock-producing. The rate of bleeding is assessed based on quantity of blood lost in the stools, appearance of the material passing through the rectum and hemodynamic state of the patient. Depending on the extent of the symptom progression at the time of diagnosis, the prognosis may vary. However, the prognosis is generally regarded as excellent in cases where symptomatic Meckel's diverticulum is treated in a timely manner. Complete recovery may be expected with surgery in majority of the cases.
Diagnosis
History and Symptoms
The presentation of Meckel's diverticulum is usually asymptomatic .The hallmark feature in symptomatic patients is the occurrence of painless lower gastrointestinal bleeding. Other symptoms of Meckel's diverticulum arise in complicated cases with features of intestinal obstruction, intussusception, volvulus and perforation. The age of presentation for approximately half of all patients is less than 10 years of age. Patients may also develop symptoms of diverticular inflammation (ie, Meckel's diverticulitis) which has a presentation similar to acute appendicitis.
Physical Examination
Patients with Meckel's diverticulum usually appear normal on physical examination. Abdominal examination of patients with Meckel's diverticulum is usually normal, even in patients with gastrointestinal bleeding. Patient develop signs of acute abdomen due to diverticular inflammation or perforation in complicated cases. These signs include Abdominal distention, abdominal tenderness, rebound tenderness and guarding.
Laboratory Findings
Other Imaging Findings
A technetium-99m (99mTc) pertechnetate scan is the investigation of choice to diagnose Meckel's diverticula. This scan detects gastric mucosa; since approximately 50% of symptomatic Meckel's diverticula have ectopic gastric (stomach) cells contained within them, this is displayed as a spot on the scan distant from the stomach itself.
Other Diagnostic Studies
Tests such as colonoscopy and screenings for bleeding disorders should be performed, and angiography can assist in determining the location and severity of bleeding.
Treatment
Medical Therapy
Iron replacement to correct anemia. In major bleeding, a blood transfusion may be needed.
Surgery
Surgical treatment consists of a resection of the affected portion of the bowel.