A Meckel's diverticulum, a true congenital diverticulum, is a slight bulge in the small intestine present at birth and a vestigial remnant of the vitelline duct. It is the most common malformation of the gastrointestinal tract and is present in approximately 2% of the population, with males more frequently experiencing symptoms.

Meckel's diverticulum was first explained by Fabricius Hildanus in the sixteenth century and later named after Johann Friedrich Meckel, who described the embryological origin of this type of diverticulum in 1809.

Signs and symptoms

The majority of people with a Meckel's diverticulum are asymptomatic. An asymptomatic Meckel's diverticulum is called a silent Meckel's diverticulum. If symptoms do occur, they typically appear before the age of two years. The most common presenting symptom is painless rectal bleeding such as melaena-like black offensive stools, followed by intestinal obstruction, volvulus and intussusception. Occasionally, Meckel's diverticulitis may present with all the features of acute appendicitis. Also, severe pain in the epigastric region is experienced by the person along with bloating in the epigastric and umbilical regions. At times, the symptoms are so painful that they may cause sleepless nights with acute pain felt in the foregut region, specifically in the epigastric and umbilical regions. In some cases, bleeding occurs without warning and may stop spontaneously. The symptoms can be extremely painful, often mistaken as just stomach pain resulting from not eating or constipation. Rarely, a Meckel's diverticulum containing ectopic pancreatic tissue can present with abdominal pain and increased serum amylase levels, mimicking acute pancreatitis.

Complications

The lifetime risk for a person with Meckel's diverticulum to develop certain complications is about 4–6%. Gastrointestinal bleeding, peritonitis or intestinal obstruction may occur in 15–30% of symptomatic people (Table 1). On rare occasions the diverticulum can herniate through the abdominal wall also known as a Littre hernia. Only 6.4% of all complications require surgical treatment, and untreated Meckel's diverticulum has a mortality rate of 2.5–15%. Symptoms may include bright red blood in stools (hematochezia), weakness, abdominal tenderness or pain, and even anaemia in some cases.

Bleeding may be caused by:

  • Ectopic gastric or pancreatic mucosa:
  1. Where diverticulum contains embryonic remnants of mucosa of other tissue types.
  2. Secretion of gastric acid or alkaline pancreatic juice from the ectopic mucosa leads to ulceration in the adjacent ileal mucosa i.e. peptic or pancreatic ulcer.
  3. Pain, bleeding or perforation of the bowel at the diverticulum may result.
  4. Mechanical stimulation may also cause erosion and ulceration.
  • Gastrointestinal bleeding may be self-limiting but chronic bleeding may lead to iron deficiency anaemia.

The appearance of stools may indicate the nature of the bleeding:

  • Tarry stools: Alteration of blood produced by slow bowel transit due to minor bleeding in upper gastrointestinal tract
  • Bright red blood stools: Brisk bleeding
  • Stools with blood streak: Anal fissure
  • "Currant jelly" stools: Ischaemia of the intestine leads to copious mucus production and may indicate that one part of the bowel invaginates into another (intussusception).

Diverticulitis

Inflammation of the diverticulum can mimic symptoms of appendicitis, i.e., periumbilical tenderness and intermittent crampy abdominal pain. Perforation of the inflamed diverticulum can result in peritonitis. Diverticulitis can also cause adhesions, leading to intestinal obstruction.

Diverticulitis may result from:

  • Association with the mesodiverticular band attaching to the diverticulum tip where torsion has occurred, causing inflammation and ischaemia.
  • Peptic ulceration resulting from ectopic gastric mucosa of the diverticulum
  • Perforation by trauma or ingested foreign material (e.g., vegetable stalks, seeds, or fish/chicken bones) that become lodged in the Meckel's diverticulum.
  • The vitelline vessels remnant that connects the diverticulum to the umbilicus may form a fibrous or twisting band (volvulus), trapping the small intestine and causing obstruction. Localised periumbilical pain may be experienced in the right lower quadrant (like appendicitis).
  • Chronic diverticulitis causing stricture
  • Strangulation of the diverticulum in the obturator foramen.
  • Tumors e.g. carcinoma: direct spread of an adenocarcinoma arising in the diverticulum may lead to obstruction
  • Lithiasis, stones that are formed in Meckel's diverticulum can:
  1. Extrude into the terminal ileum, leading to obstruction
  2. Induce local inflammation and intussusception. This occurs when the diverticulum inverts into the lumen of the ileum, due to either:
  3. An active peristaltic mechanism of the diverticulum that attempts to remove irritating factors
  4. A passive process such as the transit of food The solitary diverticulum lies on the antimesenteric border of the ileum (opposite to the mesenteric attachment) and extends into the umbilical cord of the embryo. It runs antimesenterically and has its own blood supply. It is a remnant of the connection from the yolk sac to the small intestine present during embryonic development. It is a true diverticulum, consisting of all three layers of the bowel wall: mucosa, submucosa and muscularis propria.

As the vitelline duct is made up of pluripotent cell lining, Meckel's diverticulum may harbor abnormal tissues, containing embryonic remnants of other tissue types. Jejunal, duodenal mucosa or Brunner's tissue were each found in 2% of ectopic cases. Heterotopic rests of gastric mucosa and pancreatic tissue are seen in 60% and 6% of cases respectively. Heterotopic means the displacement of an organ from its normal anatomic location. Inflammation of this Meckel's diverticulum may mimic appendicitis. Therefore, during appendectomy, ileum should be checked for the presence of Meckel's diverticulum, if it is found to be present it should be removed along with appendix.

A memory aid is the rule of 2s:

  • 2% (of the population)
  • 2 feet (proximal to the ileocecal valve)
  • 2 inches (in length)
  • 2 types of common ectopic tissue (gastric and pancreatic)
  • 2 years is the most common age at clinical presentation
  • 2:1 male:female ratio

However, the exact values for the above criteria range from 0.2–5 (for example, prevalence is probably 0.2–4%).

It can also be present as an indirect hernia, typically on the right side, where it is known as a "Hernia of Littré". A case report of strangulated umbilical hernia with Meckel's diverticulum has also been published in the literature. Furthermore, it can be attached to the umbilical region by the vitelline ligament, with the possibility of vitelline cysts, or even a patent vitelline canal forming a vitelline fistula when the umbilical cord is cut. Torsions of intestine around the intestinal stalk may also occur, leading to obstruction, ischemia, and necrosis.

Diagnosis

thumb|Technetium-99m Pertechnetate Scan with a Meckel's Diverticulum.

A technetium-99m (99mTc) pertechnetate scan, also called Meckel scan or nuclear scintigraphy scan, is the investigation of choice to diagnose Meckel's diverticula in children. This scan detects gastric mucosa; since approximately 50% of symptomatic Meckel's diverticula have ectopic gastric or pancreatic cells contained within them, this is displayed as a spot on the scan distant from the stomach itself. In children, this scan is highly accurate and noninvasive, with 95% specificity and 85% sensitivity; This scan is more accurate in children because gastric mucosa is found in 90% of bleeding diverticula; which is the most common symptom in children, not adults.

Patients with these misplaced gastric cells may experience peptic ulcers as a consequence. Therefore, other tests such as colonoscopy and screenings for bleeding disorders should be performed, and angiography can assist in determining the location and severity of bleeding. Colonoscopy might be helpful to rule out other sources of bleeding but it is not used as an identification tool. thumb|right|Angiography of a Meckel's diverticulum that presented with bleeding. Angiography might identify brisk bleeding in patients with Meckel's diverticulum. Computed tomography (CT scan) might be a useful tool to demonstrate a blind ended and inflamed structure in the mid-abdominal cavity, which is not an appendix.

Epidemiology

Meckel's diverticulum occurs in about 2% of the population.

Most cases of Meckel's diverticulum are diagnosed when complications manifest or incidentally in unrelated conditions such as laparotomy, laparoscopy or contrast study of the small intestine. Classic presentation in adults includes intestinal obstruction and inflammation of the diverticulum (diverticulitis). Painless rectal bleeding most commonly occurs in toddlers.