Congenital lesion
1. What is this congenital abnormality? 2. What is its embryological origin? 3. How may it clinically present?
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A Meckel's diverticulum is a congenital lesion that arises as a result of failure of embryonic obliteration of the vitello-intestinal duct that connects the foetal intestine to the yolk sac. The duct is normally closed by the 7th week of gestation. It is a true diverticulum (containing all layers of the gut wall) arising on the antimesenteric border of the gut. It is the commonest congenital anomaly of the small intestine found in approximately 2% of the population. The diverticulum is usually found within 1 m of the ileocaecal valve and is usually less than 12 cm in length. It frequently contains ectopic gastric mucosa. The diagnosis of a complication of a Meckel's diverticulum is rarely made preoperatively except in cases of lower gastrointestinal haemorrhage occurring in the paediatric population. Numerous complications of a Meckel's diverticulum have been described all of which occur more commonly in males. Complications include:
The treatment of all benign complications of a Meckel's diverticulum should be by diverticulectomy or a limited small bowel resection, ensuring that any ectopic gastric mucosa is resected. A diverticulum found incidentally at operation usually does not require surgical resection, except possibly when found in a young infant. A Meckel's diverticulum is the commonest cause of major lower gastrointestinal bleeding in a previously healthy infant. The bleeding is usually painless and 50% of cases occur before 2 years of age. More than 95% of bleeding Meckel's diverticulae contain ectopic gastric mucosa resulting in ulceration of either the heterotopic mucosa or the adjacent normal ileum. Bleeding may be intermittent or continuous resulting in either melaena or an exsanguinating haemorrhage. The differential diagnosis includes juvenile polyps, arteriovenous malformations and blood dyscrasias. A sodium technetium scan may be useful with the isotope taken up by the gastric mucosal parietal cells. A Meckel's diverticulum may cause intestinal obstruction by several means including intussusception, a persistent obliterated vitello-intestinal duct, adhesions secondary to previous inflammation or the diverticulum becoming strangulated in a groin hernia (Littre's hernia). Acute diverticulitis may result from peptic ulceration or due to an enterolith or foreign body within the diverticulum. The clinical presentation is often indistinguishable from that of acute appendicitis. Perforation and generalised peritonitis are seen more frequently than with acute appendicitis as the inflammatory process is less likely to be walled off. Fistulation into adjacent viscera has been described. Benign or malignant neoplasms account for 1% of the complications of Meckel's diverticulum. Carcinoid tumours and leiomyosarcomas are seen more frequently than in the remainder of the small intestine where adenocarcinoma is the commonest malignant tumour. Recent papersFa-Si-Oen P R, Roumen R M, Croiset van Uchelen F A. Complications and management of Meckel’s diverticulum: a review. Eur J Surg 1999; 165: 674-8. Bemelman W A, Hugenholtz E, Heij H A, Wiersma P H, Obertop H. Meckel's diverticulum in Amsterdam: experience in 136 patients. World J Surg 1995; 19: 734-746.
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