Meckel Diverticulum

The commonest congenital anomaly of the gastrointestinal tract, a persistent remnant of the embryological omphalomesenteric (vitelline) duct.

It is classically summarised by the "rule of twos". It occurs in approximately two percent of the population and lies within approximately two feet of the ileocaecal valve. It is approximately two inches in length and twice as common in males. When symptomatic, it typically presents before the age of two years.

These figures are approximate, generalised clinical teaching rather than precise, universally applicable statistics.

The majority of affected individuals remain entirely asymptomatic throughout life. A minority develop characteristic complications: painless lower gastrointestinal bleeding (from ectopic gastric mucosa within the diverticulum), intestinal obstruction, and, less commonly, diverticulitis mimicking acute appendicitis.

Pathophysiology

• The omphalomesenteric duct connects the developing midgut to the yolk sac during early gestation. Failure of complete regression leaves a persistent, true diverticulum arising from the antimesenteric border of the ileum.
• It contains all layers of the normal bowel wall. This distinguishes it from the more common acquired false diverticula (such as colonic diverticula), which lack the full bowel wall thickness.
• Ectopic tissue is frequently present within the diverticulum. The most common is gastric mucosa, present in a substantial proportion of symptomatic cases. Pancreatic tissue is less common.
• Ectopic gastric mucosa secretes acid, which can cause peptic ulceration of the adjacent, unprotected ileal mucosa. This accounts for painless gastrointestinal bleeding, the commonest symptomatic presentation.
• The diverticulum, or a persistent fibrous band connecting it to the umbilicus (a remnant of the more extensive duct), can act as a lead point for intussusception.
• It can also be a point of fixation around which the bowel twists or becomes obstructed. This accounts for intestinal obstruction.

• Painless, typically brisk, lower gastrointestinal bleeding is the classic and commonest symptomatic presentation. It appears as maroon stool or, in more significant bleeding, frankly bloody stool. It is particularly characteristic in young children.
• It reflects peptic ulceration of the ileal mucosa adjacent to ectopic gastric tissue within the diverticulum.
• The bleeding is characteristically painless and often intermittent. It can be significant enough to produce haemodynamically relevant blood loss and anaemia.
• Intestinal obstruction results from intussusception with the diverticulum as a lead point, volvulus around a persistent fibrous band, or, less commonly, herniation of bowel through an associated defect.
• It presents with the usual features of bowel obstruction: colicky abdominal pain, vomiting, and abdominal distension.
• Meckel diverticulitis is inflammation of the diverticulum itself. The picture is frequently indistinguishable from acute appendicitis, with periumbilical or right-sided abdominal pain, fever, and localised tenderness.
• It is an important source of diagnostic confusion. Where appendicitis is suspected clinically but the appendix is found to be normal at surgical exploration, examine the terminal ileum carefully for an underlying Meckel diverticulum.
• The great majority of individuals with a Meckel diverticulum remain asymptomatic throughout life. It is identified only incidentally, during imaging or surgery for an unrelated indication.
• The mere presence of this common anatomical variant does not in itself indicate any need for intervention in the absence of symptoms or complications.

• A technetium-99m pertechnetate scan (Meckel scan) is the standard, specific diagnostic investigation for suspected Meckel diverticulum presenting with painless gastrointestinal bleeding. It selectively concentrates within ectopic gastric mucosa.
• Sensitivity is substantially enhanced by the presence of ectopic gastric mucosa, the cause of bleeding in the great majority of symptomatic cases. The scan is therefore most useful and reliable in this presentation.
• Where intestinal obstruction is the presenting concern, standard imaging for bowel obstruction is pursued, as for obstruction from any cause. This includes abdominal radiography and, where indicated, ultrasound or computed tomography.
• The underlying Meckel diverticulum is frequently identified only at subsequent surgical exploration rather than on preoperative imaging alone.
• Where Meckel diverticulitis is suspected, or the presentation closely mimics acute appendicitis, the diagnosis is frequently established at surgical exploration for suspected appendicitis.
• Where the appendix itself is found to be normal, examine the terminal ileum carefully for a Meckel diverticulum. This is a standard component of surgical technique in this scenario.
• Assess haemodynamic status and the severity of any associated anaemia, including full blood count. This is essential in the bleeding presentation.
• Where bleeding is significant, ongoing, or haemodynamically significant, provide appropriate resuscitation and blood product support.

• Surgical resection is the definitive treatment for symptomatic Meckel diverticulum. It is performed by an open or laparoscopic approach, according to the clinical presentation, degree of urgency, and surgeon expertise and preference.
• It typically comprises diverticulectomy. Segmental small bowel resection with primary anastomosis is used particularly where there is a broad-based diverticulum, or ileal ulceration or inflammation extending beyond the diverticulum itself.
• Bleeding presentations require initial resuscitation and stabilisation, including blood product support where clinically indicated by the severity of blood loss.
• Definitive surgical resection follows once the diagnosis is confirmed. Surgery is generally relatively urgent, though not typically immediately emergency, once the patient is stabilised. The bleeding is characteristically intermittent but may recur and be significant.
• Intestinal obstruction related to a Meckel diverticulum (from intussusception, volvulus, or another mechanism) is managed on the standard principles for bowel obstruction.
• Surgical exploration and resection of the underlying diverticulum is the definitive treatment, once the obstruction has been addressed or is being concurrently managed at surgery.
• Meckel diverticulitis is managed with surgical resection, following similar principles to acute appendicitis. The presentations overlap closely, and the diagnosis is frequently made at exploration for suspected appendicitis.
• Incidental identification of an asymptomatic Meckel diverticulum during surgery or imaging for an unrelated indication generally does not warrant prophylactic resection. The lifetime risk of symptomatic complication is relatively low and is balanced against the risks of additional, otherwise unnecessary surgery.
• The decision may be individualised according to risk factors seen on direct inspection during an unrelated procedure. These include a notably narrow diverticular neck, a palpable firm area suggesting ectopic tissue, or other concerning features.
• The operating surgeon generally decides on incidental resection from the direct intraoperative findings and clinical context.
• Postoperative recovery and follow up follow standard principles for abdominal surgery in children. Correct any associated anaemia and confirm resolution of the presenting symptoms.