Meckel's Diverticulum

What is Meckel's diverticulum?

Early in pregnancy, a tube called the vitelline (omphalomesenteric) duct connects the baby's gut to the yolk sac. It normally disappears by about the seventh week. If part of it stays, it forms a pouch sticking out from the ileum, the end of the small intestine. That pouch is a Meckel's diverticulum.

It is a true diverticulum: its wall contains all layers of the bowel wall. In about half of symptomatic cases, the pouch contains ectopic tissue, cells that belong elsewhere, most often stomach lining that produces acid, or pancreatic tissue.

The rule of 2s

Medical students learn Meckel's diverticulum by the "rule of 2s". These are approximations, not exact figures:

• Present in about 2% of the population
• Located about 2 feet (60 cm) from the junction of the small and large intestine
• About 2 inches (5 cm) long
• Often contains 2 types of ectopic tissue (stomach and pancreas)
• Symptoms usually start before age 2
• Symptoms are about 2 times more common in males

Symptoms

Most people never know they have one. When problems occur, they fall into three main groups:

Bleeding

The most common presentation in young children. Acid from stomach-type tissue in the pouch causes an ulcer in the neighboring ileum lining, which bleeds.

• Sudden painless rectal bleeding: bright red, brick red or maroon stool
• Sometimes dark, tarry stool (melena)
• Paleness, tiredness or fainting from blood loss
• Slow bleeding may only show up as iron deficiency anemia

Obstruction

More common in older children and adults.

• Colicky abdominal pain, vomiting and a swollen belly
• Causes include intussusception, where the diverticulum leads one part of the bowel to telescope into the next; volvulus, twisting of the bowel around a fibrous band from the pouch to the navel; and trapping of the pouch in a hernia (Littre hernia)

Inflammation (Meckel's diverticulitis)

• Pain near the navel or lower right belly, fever and vomiting
• It looks almost identical to appendicitis, and is often discovered during surgery for presumed appendicitis
• It can rarely perforate

Who is affected?

Meckel's diverticulum is present from birth. About half of symptomatic cases occur before age 2, and most before 10. Symptoms in adults are less common and more often involve obstruction or inflammation than bleeding. Very rarely, tumors such as carcinoid (neuroendocrine) tumors arise in the pouch.

Diagnosis

A Meckel's diverticulum is hard to see on standard tests because it is small and hidden among loops of bowel.

• Meckel scan (technetium-99m pertechnetate scintigraphy): a small amount of radioactive tracer is injected into a vein. Stomach-type tissue absorbs it and shows up as a hot spot in the lower belly. It is the test of choice in children with painless rectal bleeding. Accuracy is high in children but lower in adults, and the scan only shows pouches containing stomach tissue.
• Blood tests: a blood count to check for anemia, and blood grouping in case a transfusion is needed.
• Ultrasound: often the first test for belly pain or suspected intussusception in children.
• CT scan: useful for obstruction or inflammation, especially in adults.
• CT angiography or capsule endoscopy: for ongoing bleeding when other tests are negative.
• Laparoscopy: keyhole surgery can both diagnose and treat when imaging is inconclusive.

Treatment

Symptomatic Meckel's diverticulum

Surgery is the definitive treatment.

• Diverticulectomy: removing the pouch, or
• Segmental small bowel resection: removing the pouch with a short section of bowel, especially when bleeding has come from an ulcer in the neighboring bowel or the base is wide or inflamed

Most operations are done laparoscopically. Children typically stay in the hospital for a few days. Before surgery, bleeding may need fluids and a blood transfusion, and acid-suppressing medicine may be given.

Pouches found by chance

When a Meckel's diverticulum is discovered incidentally during surgery for something else, whether to remove it is debated. Surgeons tend to remove it in children and younger adults, and when it feels thickened, has a narrow base or is attached to the navel by a band. In older adults, many surgeons leave a normal-looking one alone.

Complications

• Severe bleeding needing transfusion
• Bowel obstruction, intussusception and volvulus
• Perforation and peritonitis
• Surgical complications such as infection, leaks or adhesions, which are uncommon

Outlook

The outlook after surgery is excellent. Once the pouch is removed, it cannot return, and long-term problems are rare.

Frequently asked questions

What is the rule of 2s for Meckel's diverticulum?

It is a memory aid: Meckel's diverticulum occurs in about 2% of people, about 2 feet from the end of the small intestine, about 2 inches long, can contain 2 types of abnormal tissue, usually causes symptoms before age 2, and is about 2 times more common in males with symptoms.

What are the symptoms of Meckel's diverticulum?

Most people have no symptoms. In young children, the classic sign is sudden painless rectal bleeding that may be red or maroon. Other presentations are bowel obstruction with colicky pain and vomiting, and inflammation that mimics appendicitis with pain, fever and vomiting.

Can adults have Meckel's diverticulum?

Yes. Everyone who has it was born with it, but some first have symptoms as adults. In adults, obstruction and inflammation are more common than bleeding, and the Meckel scan is less accurate, so CT scans or keyhole surgery are often used for diagnosis.

What is a Meckel scan?

A Meckel scan is a nuclear medicine test in which a small amount of radioactive tracer called technetium-99m pertechnetate is injected into a vein. Stomach-type tissue takes it up, so a pouch containing that tissue shows as a bright spot in the lower belly on a gamma camera.

Is Meckel's diverticulum serious?

Usually not. Most people with one never have symptoms. When it does cause bleeding, obstruction or inflammation, it can be serious and needs prompt surgery, but the operation cures the problem and long-term outcomes are excellent.