Meckel diverticulum

• Meckel diverticulum is a saclike outpouching of the terminal ileum left behind when the embryonic vitelline (omphalomesenteric) duct fails to close; it is the commonest congenital abnormality of the gastrointestinal tract and is present in roughly 1 to 3% of people.
• It is usually silent. When it causes trouble it does so in three main ways: painless heavy bleeding from acid-secreting ectopic gastric mucosa; intestinal obstruction (often from a fibrous vitelline band); and diverticulitis that can look exactly like appendicitis.
• The classic teaching "rule of twos" (2% of people, 2 feet from the valve, 2 inches long, 2:1 male:female, symptomatic before age 2) is only a memory aid; recent cohort data show more than half of affected children are diagnosed after 5 years of age.
• The best first test for bleeding is a technetium-99m pertechnetate (Meckel) scan, which picks up ectopic gastric mucosa; the cure is surgical resection, urgently when there is obstruction, perforation or shock.
• A negative scan does not exclude the diagnosis: sensitivity is of the order of three-quarters, so persisting clinical suspicion warrants repeat scanning or cross-sectional imaging rather than reassurance.

By the end of this page you should be able to:

1. Explain how failure of the vitelline duct produces a true diverticulum, and describe its typical position, size and blood supply.
2. State the rule of twos and contrast it with the modern evidence on age at presentation, and explain which patients are usually missed.
3. Explain why ectopic gastric mucosa causes bleeding and why ectopic pancreatic tissue behaves differently.
4. Describe the presenting patterns of bleeding, obstruction, diverticulitis and umbilical abnormalities, and how diverticulitis mimics appendicitis.
5. Plan the investigation of suspected Meckel diverticulum, interpret a Meckel scan (including false negatives), and use CT and ultrasound sensibly.
6. Manage bleeding, obstruction and incidental diverticulum, and outline the unresolved debate about incidental resection.
7. Build a differential diagnosis for lower gastrointestinal bleeding in a child.

"Meckel diverticulum" is the standard spelling on this page; "Meckel's diverticulum" is the same thing. The suffix "-itis" is reserved for the complication, Meckel diverticulitis.

A true diverticulum matters clinically because it shares the blood supply of the ileum through the persistent vitelline (omphalomesenteric) artery, which can leave a fibrous mesodiverticular band; loops of bowel can become trapped under that band and strangulate. ^[8]

By convention the page discusses the common form in children and young people. Adults are affected too, but the presentation shifts toward obstruction and, rarely, neoplasia.

Among congenital malformations of the gut, Meckel diverticulum is the commonest. ^[3] Most recent reviews put its prevalence at about 1 to 3% of the population, ^{[5] [8]} whereas the older memory aid rounds it to 2%. ^[1] A large recent cohort quoted 0.5 to 3%. ^[2] These ranges reflect different methods (autopsy versus surgical series) rather than a true difference in disease frequency.

Most affected individuals never know they have it: it is found incidentally at operation or imaging for something else. ^[3] Reported symptomatic rates vary from about 1% ^[3] to 4% ^[8]. One systematic review of incidental diverticula put the lifetime complication risk at 4 to 6%. ^[9]; a paediatric surgical survey quoted 2 to 4% of affected individuals developing symptoms over a lifetime. ^[10] A nuclear medicine review noted that 80% of patients with symptoms are under 15 years of age. ^[6]

Sex is male-predominant, but how strongly depends on the source: the classical teaching is a 2 to 1 male:female ratio, ^{[1] [3]} whereas one large modern cohort found males comprising up to 75% of cases. ^[2] The difference probably reflects referral (symptomatic diverticula are more often male) rather than biology.

Age is where teaching has changed most. The classical description places Meckel diverticulum in toddlers. A 2026 population-based study found that more than half of children with a primary diagnosis (64.8% of 1004 patients) were diagnosed after 5 years of age, and that presentation shifted with age: children 5 years and under usually bled (painless rectal bleeding in 38.9%), whereas older children more often had abdominal pain. ^[2] Consensus guidelines of the Society of Nuclear Medicine and Molecular Imaging and the European Association of Nuclear Medicine state that more than half of patients whose Meckel diverticulum presents with lower gastrointestinal bleeding do so by 2 years of age. ^[2] Both can be true: the bleeders present early, but the whole population is diagnosed late. Hold both facts and you will not be surprised by the older child.

There is no known modifiable risk factor and no inheritance pattern in the usual form. The diverticulum is a developmental accident rather than a disease one acquires. ^[3] Female sex is not protective, but males predominate among symptomatic cases. ^{[2] [3]}

During early development the midgut is connected to the yolk sac by the vitelline (omphalomesenteric) duct. The duct normally narrows and disappears during the fifth week of gestation. ^{[3] [8]} When it only partly obliterates, the part attached to the ileum persists as a diverticulum; the umbilical end may persist instead as a fibrous band, cyst or an umbilical sinus. The completeness of the failure determines the phenotype.

The embryological logic explains three clinical features:

• A true diverticulum. Unlike a colonic diverticulum, Meckel diverticulum contains mucosa, submucosa and muscularis propria, because it is a persistent piece of the original bowel. ^[3]
• Antimesenteric position. It buds from the side of the ileum opposite the mesentery, where the vitelline artery once entered. ^[3]
• Heterotopic mucosa. The vitelline duct is lined by pluripotent cells, so the diverticulum can seed tissues that do not belong in the ileum. ^[3]

Its blood supply, the persistent vitelline (omphalomesenteric) artery, can also leave a mesodiverticular band running from the diverticulum to the mesentery or umbilicus; bowel can herniate beneath it and strangulate. ^[8]

A spectrum of vitelline duct remnants is worth keeping in mind, because all of them present in infants:

• Meckel diverticulum (the ileal pouch).
• A persistent vitelline duct or fibrous band, which can cause obstruction without a pouch.
• An umbilical cyst or sinus.
• A prolapse of ileum through the umbilicus (prolapsed Meckel diverticulum), presenting as umbilical discharge or a red periumbilical mass. ^[3]

The diverticulum is typically found on the antimesenteric border of the terminal ileum, within about 60 cm (2 feet) of the ileocaecal valve; some series describe a range up to about 100 cm. ^{[3] [5]} It is classically short (a few centimetres), with a narrow neck, though it can be larger. ^{[1] [3]} Mean size is often quoted in the region of 2 cm in diameter. ^[3]

Its inner lining is usually ileal mucosa, but heterotopic tissue is common. Reported rates differ substantially between sources: one review described heterotopic mucosa in up to 30 to 50% of cases, ^[3] while a recent large cohort found it in up to 80%. ^[2] Either way, gastric mucosa is the most common ectopic tissue. Its reported prevalence also ranges widely, from 20% up to 60 to 80% of diverticula in different series. ^{[2] [3] [6]} Pancreatic tissue occurs in about 1 to 16% of cases. ^{[3] [4] [2]} Much rarer ectopic tissues include colonic, duodenal, endometrial and biliary epithelium. ^[3]

Two different sources of the acid-forming tissue give the same clinical picture through different frequency data: one may cite 1 to 6%, ^[4] another 5 to 16%. ^[2] Both are literature ranges and there is no single correct figure, so the safest statement is that gastric mucosa predominates and pancreatic tissue is present in a minority.

Symptomatic diverticula contain heterotopic tissue far more often than asymptomatic ones (a roughly tenfold higher incidence), yet only 50 to 60% of patients with heterotopic tissue ever become symptomatic. ^[2]

The two mechanisms that matter most can both be reasoned from the histology.

Acid secretion and bleeding. Ectopic gastric mucosa contains parietal cells that secrete acid and pepsin into a pouch that empties poorly. The adjacent ileal mucosa is not built to withstand acid, so it ulcerates. The bleeding is therefore a chemical mucosal injury, not a structural tear: it can be slow and occult (anaemia, positive stool blood) or sudden and massive (painless haematochezia, fainting, shock). ^[3] Vascular malformations are not the usual cause. The amount of bleeding often seems out of proportion to the size of the pouch. Recent paediatric data also describe an inverted U-shaped relationship between diverticular width and bleeding severity, so the size of the pouch appears to influence how much blood is shed. ^[11] Ulceration of the adjacent ileal mucosa by acid from ectopic gastric mucosa is the reason segmental resection rather than simple diverticulectomy is preferred in bleeding cases: the ulcerated adjacent bowel must come out as well. ^[3]

Because the problem is acid, acid suppression is therapeutic curiosity but not cure: proton pump inhibitors may settle bleeding while arrangements for definitive resection are made, but they do not remove the tissue, and rebleeding is expected.

Pancreatic tissue behaves differently. Ectopic pancreatic tissue secretes enzymes that can inflame local mucosa, but it does not create the brisk ulcerative bleeding of gastric tissue. A diverticulum with pancreatic ectopia is less likely to present with rectal bleeding and more likely to present with obstruction, intussusception or diverticulitis. ^[3]

Obstruction. Several mechanisms produce it, all mechanical:

• A mesodiverticular or vitelline fibrous band can trap a loop of small bowel and produce a simple or strangulated obstruction. ^{[3] [8]}
• The diverticulum can act as a lead point for intussusception, particularly ileoileal or ileocolic, usually in slightly older children. ^[3]
• Volvulus of the intestine around a persistent vitelline duct or band. ^[8]
• Inversion of the diverticulum into the lumen (inverted Meckel), which can mimic a polyp.
• Stricture from chronic inflammation or ischaemia.
• An enterolith or concretion within the pouch. ^[8]

Therefore a child or young adult with small bowel obstruction and no prior surgery or hernia should have Meckel diverticulum considered early. ^[8]

Diverticulitis and perforation. Ectopic gastric secretion inflames the wall; the pouch becomes acutely inflamed, mimicking appendicitis, and because it lies in the right lower quadrant it often presents as acute right-sided abdominal pain with fever and vomiting. Perforation from acid-induced ileal ulceration can release air into the peritoneum and give pneumoperitoneum on imaging. ^[3]

The umbilical presentations are explained by the other end of the duct: a persistently discharging or protruding remnant at the umbilicus, a subumbilical cyst communicating with the bowel, or a prolapsed pouch. These are easily mistaken for umbilical granuloma or a patent urachus. ^[3]

Most people with Meckel diverticulum never have symptoms. ^[3] Symptomatic patients present as paediatric emergencies in most of the literature, although presentation as late as the third decade (and beyond) occurs. Symptomatic forms cluster into four presentations below; the complication frequencies have been estimated at roughly bleeding 40%, obstruction 30%, diverticulitis 20% and perforation 10%, recognising that these proportions come from selected surgical and case series. ^[3]

This is the classical and most high-stakes presentation, especially in young children. ^{[2] [3] [6]} Bright red or maroon blood per rectum, sometimes with clots, in a child who is otherwise well between bleeds; or melena when the source is higher. The bleeding is often brisk enough to produce pallor, tachycardia and cool peripheries, but the abdomen is soft and non-tender, which should direct attention away from an inflammatory cause. Chronic occult bleeding presents as unexplained iron deficiency anaemia with fatigue and abdominal pain. ^[3]

It classically begins before 2 years of age (the consensus guideline figure), ^[2] but large modern series still show rectal bleeding in 38.9% of under-5s diagnosed with Meckel diverticulum, falling to 10% in those diagnosed after 15 years. ^[2]

Vomiting (often bilious), colicky central abdominal pain, distension and constipation, with air-fluid levels on plain X-ray. ^[8] This is an adult as much as a paediatric presentation. Any delay in surgery of 36 hours or more once strangulation is present roughly triples mortality, from about 8% to about 25%. ^[8]

Right-sided or central colicky pain, low-grade fever, anorexia, vomiting and tenderness. ^[3] Because the diverticulum sits close to the ileocaecal valve, it is commonly mistaken for appendicitis before operation; the diagnosis is often made only on the operating table or on histology. ^[3]

A moist or persistently discharging umbilicus, a subumbilical mass, or a red protruding periumbilical lump in an infant should raise Meckel diverticulum as a possibility, alongside umbilical granuloma and patent urachus. ^[3]

Children whose diverticulum bleeds have lower haemoglobin than those with another cause of bleeding: in one series of 94 children scanned for suspected Meckel diverticulum, mean haemoglobin was 88.7 g per L in those with the diagnosis versus 107.2 g per L in those without. ^[5] Anaemia in a child with painless rectal bleeding is therefore both a marker of severity and a clue. Respiratory or cardiovascular compromise must be assessed first.

Meckel diverticulum is one of several causes of lower gastrointestinal bleeding in children. It is a small-bowel source and colonoscopy will not usually see it; the clue is often painless blood in a child plus anaemia, with a positive Meckel scan. A common clinical error is to stop looking for Meckel because a more conspicuous diagnosis (juvenile polyp, inflammatory bowel disease) has been found elsewhere; the two can coexist, and the colonoscopy should still have been done to exclude a second source when bleeding persists.

In a recent colonoscopy series of children investigated for lower gastrointestinal bleeding, inflammatory bowel disease accounted for 29.5%, anal fissure for 23.5% and polypoid lesions for 11.2% of diagnoses; Meckel diverticulum is not found at colonoscopy. ^[12] A Meckel scan and, when bleeding is brisk, cross-sectional imaging or device-assisted enteroscopy are the routes to it.

1. Resuscitate and stabilise first if there is active bleeding (airway protection, IV access, fluids, cross-match).
2. If the Meckel diverticulum is a possibility, arrange a technetium-99m pertechnetate scan before barium or endoscopy (see below).
3. If bleeding is brisk and ongoing, CT angiography may localise it; if it is obscure, capsule endoscopy or device-assisted enteroscopy may be needed. ^[8]
4. In obstruction or suspected diverticulitis, plain films and CT of the abdomen are more useful than nuclear medicine.

A full blood count will show how much blood has been lost; one paediatric series reported mean haemoglobin of 88.7 g per L in children with Meckel diverticulum versus 107.2 g per L in those with another diagnosis. ^[5] Coagulation studies, blood group and cross-match, and iron studies belong in the panel. ^[5]

The scan detects ectopic gastric mucosa: pertechnetate is taken up by parietal and mucus cells of gastric mucosa, wherever they are. Because about 90% of bleeding Meckel diverticula harbour ectopic mucosa, a positive scan is strong evidence and a negative one does not settle the question. ^{[5] [6]}

Preparation and technique from practice and recent studies:

• Fast 3 to 6 hours beforehand. ^{[5] [7]}
• Avoid perchlorate and laxatives beforehand; they can wash out or interfere with tracer. ^[5]
• Premedicate with an acid-suppressing agent 30 minutes before the scan to improve retention of tracer in gastric mucosa and ectopic gastric mucosa and reduce luminal washout. Ranitidine 1 mg per kg intravenously (maximum 50 mg) was the standard but has been withdrawn in many markets because of nitrosamine contamination; intravenous pantoprazole (20 mg if under 10 years, 40 mg if 10 years or older) has shown equivalent scan quality. ^[7]
• Give technetium-99m pertechnetate intravenously at 1.85 megabecquerels per kg (minimum 18.5 MBq). ^{[5] [7]}
• Acquire dynamic anterior images over at least 30 minutes and static images at 5, 10, 20, 30, 60 and 120 minutes, with lateral and posterior views to localise renal pelvic activity, and post-void images if the bladder overlaps. ^{[5] [7]}
• A positive scan shows a focal area of uptake that appears with the gastric uptake and increases with it over time, in the right lower abdomen or pelvis, not attributable to physiological renal, urinary or vascular activity. ^[5]

Diagnostic accuracy data:

• In a 12-year single-centre series of 94 children, sensitivity 76.9%, specificity 100.0%, positive predictive value 100.0%, negative predictive value 91.9%, overall accuracy 93.6%. ^[5]
• A 2023 systematic review and meta-analysis of 16 studies (1115 children) reported pooled sensitivity 0.80 and pooled specificity 0.95. ^[6]
• Across the literature sensitivity ranges from about 60 to 100% and specificity from 22 to 100%, and an initial scan can be falsely negative in 50% in some series. ^[5]
• Six of 74 negative scans in the 12-year series were false negatives, all later shown at surgery to contain ectopic gastric mucosa. ^[5]

Because the scan is not perfectly sensitive, children with a presentation strongly suggesting Meckel diverticulum and a negative scan need further steps rather than reassurance: repeat scintigraphy (one of three repeat scans turned positive in the series, attributed to tracer washout during active bleeding), SPECT/CT for anatomical localisation of equivocal foci, and, in severe haematochezia or ongoing instability, laparoscopy or laparotomy. ^[5]

• CT of the abdomen is more useful in older children and in obstructive presentations; more than half of patients in all age groups had Meckel diverticulum detectable on CT using the criteria of blind-ending tubular pouch, right lower quadrant mass, small-bowel obstruction, enterolith or intussusception, and detection rises with age. ^[2]
• Ultrasound of the ileocaecal region is helpful when intussusception is possible; it may show a subumbilical mass communicating with bowel or dilated loops, but it is operator-dependent and non-specific. ^{[2] [7]}
• Colonoscopy rarely visualises an ileal diverticulum; its role is to rule out IBD and polyps if bleeding is not explained. ^[2]
• Capsule endoscopy and device-assisted enteroscopy are reserved for obscure bleeding after a negative Meckel scan. ^[8]

There is no single universally adopted diagnostic score for Meckel diverticulum. The diagnosis rests on histopathological demonstration of a true ileal diverticulum, with or without heterotopic mucosa, taken together with the clinical picture. Severity is clinical rather than radiological: severe haematochezia (anaemia, haemodynamic instability), strangulated obstruction or peritonitis are the emergencies. SPECT/CT improves confidence in an equivocal scan by localising tracer to a blind-ending pouch and by excluding alternatives such as a gastric duplication, vascular malformation or intussusception. ^[5]

• Resuscitate. Airway protection if massive rectal bleeding; large-bore intravenous access; crystalloid and blood products guided by haemoglobin, haemodynamics and local massive transfusion practice. Keep the patient warm and reassess frequently.
• Gastric acid suppression is both a diagnostic adjunct and a temporising measure: a proton pump inhibitor may reduce acid secretion from ectopic gastric mucosa and can buy time before operation, but it does not remove the tissue and rebleeding is expected. ^[7]
• Stop anticoagulant and antiplatelet drugs where the bleeding is major, balancing thrombotic risk.
• Analgesia, nil by mouth and nasogastric decompression in obstruction.

Surgery is the definitive treatment for symptomatic Meckel diverticulum. ^{[3] [8]} The choice of resection depends on the integrity of the diverticular base and proximal ileum and on where any ectopic tissue is:

• Diverticulectomy is acceptable when the base is narrow and ectopic tissue is confined to the body or tip. ^[8]
• Wedge or segmental ileal resection is preferred in bleeding with ectopic gastric mucosa (to remove the adjacent ulcerated ileum), in broad-based diverticula, in diverticulitis, and when the pouch is involved with tumour. ^{[3] [8]}
• In critically ill patients with perforation and systemic sepsis, a temporary ileostomy with delayed restoration of continuity may be life-saving. ^[3]

Handle the bowel as little as possible before clamping in a bleed, and operate promptly: early diagnosis is critical because a delay of 36 hours or more in strangulation roughly triples mortality. ^[8] Laparoscopic or laparoscopy-assisted resection is commonly used in experienced hands, and CT can guide the approach when obstruction is the presentation. ^[8]

Avoid proton pump inhibitors alone being allowed to delay surgery once the diagnosis is confirmed; they are a bridge.

This is a genuinely unresolved question. The lifetime risk of a complication has been estimated at 2 to 4% ^[10] and a systematic review at 4 to 6%. ^[9] Traditional teaching avoids resecting a broad-based, asymptomatic diverticulum; more recent evidence supports removing it when the patient's condition allows, particularly in younger patients, because of future bleeding and, rarely, malignant potential (reported metastatic disease in 26 to 33% of malignancy-associated cases, with neuroendocrine tumours the commonest reported malignancy). ^{[3] [9] [10]} Current evidence is insufficient to demand routine prophylactic resection, and most surgeons individualise the decision using risk features such as a narrow base, palpable heterotopic tissue, fibrous bands and the patient's age, with traditional teaching also cautious about long diverticula (reflecting the rule of twos). ^{[9] [10]}

Where resources permit, single-stage resection and anastomosis is standard. Intra-operative frozen section helps confirm ectopic tissue and clearance. Send every resected pouch for histology. ^{[2] [3]}

No fixed surveillance protocol applies to simple resected disease; the cure is surgical. In recurrent, multiple or syndrome-associated diverticula (for example with other congenital anomalies) reassess for associated conditions.

• Massive rectal or ileal ulceration bleeding, with iron deficiency anaemia and haemodynamic compromise. ^[3]
• Intestinal obstruction from a mesodiverticular band, volvulus, intussusception with the diverticulum as lead point, an inverted pouch, stricture or enterolith. ^{[3] [8]}
• Diverticulitis mimicking appendicitis, sometimes progressing to perforation and peritonitis. ^[3]
• Perforation from acid-induced ulceration, which can give pneumoperitoneum on imaging. ^[3]
• Intussusception with the diverticulum acting as the lead point; this is one of the common pathologic lead points in older children. ^[3]
• Umbilical discharge, prolapse or sinus in infants, mistaken for granuloma or urachal anomalies. ^[3]
• Malignant change within the pouch is rare but reported, most often neuroendocrine tumour, followed by gastrointestinal stromal tumour, adenocarcinoma, lymphoma and metastasis. ^[3]

Resection removes the responsible ectopic tissue and the ulcerated adjacent bowel, and is curative for the symptomatic diverticulum. Recurrence of symptoms after adequate resection is unusual. Outcomes reported in individual small case series are good, though the literature is dominated by single-centre studies. ^{[3] [8]}

Neonates and infants. The presentation is often not intestinal at all: persistent umbilical discharge, a subumbilical cyst or mass communicating with the bowel, or a prolapsed ileal pouch through the umbilicus. ^[3] These need careful differentiation from umbilical granuloma and patent urachus. ^[3]

Children. They are the central population of this page, and bleeding is the leading presentation in young children; see the epidemiology section above.

Adolescents and young adults. Increasingly present with abdominal pain or obstruction rather than bleeding, and are more often diagnosed by CT. ^[2] Meckel diverticulum should remain in the differential of unexplained small bowel obstruction at any age. ^[8]

Pregnancy and adults. The same principles of surgical resection apply. Malignancy and diverticulitis become relatively more common presentations in adults, though these are rare. ^[3]

• Meckel scanning may not be available; CT and ultrasound become the main tools, but either can miss an uninflamed pouch. Clinical suspicion of painless bleeding with anaemia in a child, or small bowel obstruction in a patient with no prior surgery or hernia, should still point toward Meckel diverticulum and toward early surgical referral. ^{[2] [5]}
• Oral acid suppression can act as a bridge while transfer is arranged but is not definitive. ^[7]
• If imaging is unavailable, an obstructed patient with no hernia or adhesions and no appendicitis rises high on the diagnostic list; delay past 36 hours in strangulation is dangerous. ^[8]
• Every resected pouch should still go to the laboratory; histology is how heterotopic mucosa and, rarely, malignancy are identified. ^{[2] [3]}
• Even small centres can run the operation: resection and primary anastomosis is the standard. ^[3]

• Meckel diverticulum is the most common congenital anomaly of the gastrointestinal tract, present in about 1 to 3% of people, usually silent.
• It is a true ileal diverticulum, on the antimesenteric border, from incomplete obliteration of the embryonic vitelline duct in the fifth week.
• The traditional rule of twos is a memory aid, not a clinical rule; modern cohorts show most diagnoses after age 5, and more than half of children presenting with lower gastrointestinal bleeding present by age 2.
• Gastric ectopic mucosa secretes acid into adjacent ileum and produces the classic painless rectal bleeding; pancreatic tissue is far less likely to bleed.
• Heterotopic mucosa is present in roughly 30 to 80% of resected diverticula; gastric mucosa is the commonest, pancreatic the next.
• The three symptomatic patterns are bleeding, obstruction and diverticulitis, the last of which commonly mimics appendicitis.
• In children under 5 with Meckel diverticulum, 38.9% present with painless rectal bleeding; over 15 years, only 10% do. ^[2]
• Technetium-99m pertechnetate scanning is the most useful non-invasive test for ectopic gastric mucosa, with sensitivity around 77 to 80% pooled and specificity around 95 to 100%.
• A negative scan does not exclude the diagnosis; repeat the scan or add SPECT/CT if suspicion is high.
• Surgery is the definitive treatment; choose diverticulectomy or segmental resection by base width and ectopic tissue site, and do not let imaging delay operation for obstruction, strangulation or perforation.
• Incidental diverticula found at unrelated operations pose an unresolved management question; decisions should be individualised.
• Meckel diverticulum is a standard item on the list of small-bowel causes of lower gastrointestinal bleeding in children.

Intussusception; Appendicitis; Gastrointestinal bleeding; Congenital malformations; Small bowel obstruction; Hernias; Abdominal pain in children.