Meckel's diverticulum

A Meckel's diverticulum is a true congenital diverticulum in that it consists of al three layers of the intestine. It is a remnant of the primitive yolk sac (the viteline duct) which occurs on the ante-mesenteric border of the ileum.

Historical background

• 1st described by Littre in a hernial sac in 1700, 81 years before Meckel was born.
• Diverticulum described by Johann Meckel, Prof. of Anatomy, Germany.

Embryology and Anatomy

• Remnant of the viteline duct which connects the yolk sac to the digestive tube of an embryo. It appears towards the fourth embryonic week and should obliterate by seven weeks after birth. Persistance results in a Meckle's diverticulum.
• May be connected by a fibrous band to the umbilicus which is remnant of the vitello-intestinal duct. The bowel can tort around this point leading to obstruction.
• The Vitello-intestinal duct may persist completely or incompletely which leads to formation of:

1. Meckel's diverticulum (commonest)
2. Complete - umbilical fistula.
3. Incomplete - vitello-intestinal fistula.
4. Enterocystoma (encysted fluid collection in the band)

Rule of twos

Although not strictly acurate the rule of two provides a useful aide menior. A Meckel's occurs in 2% of the population; 2 feet from the ileo-ceacal valve; is 2 inches in lenght; is symtomatic in 2%; and 2 times as many male are affected than females.

Actually the incidence is equal amongst males and females it is just that males are more commonly symptomatic.

It is important to note that a Meckel's diverticulum has it's own artery and 20% will contain ectopic mucosa. This can be gastric, pancreatic or colonic which is often hyperplastic & extends into the surrounding ileum.

Presentation

• Acute peptic ulceration - with vomiting, and bleeding P/R with melena. Vomitus does not have blood.
• Chronic peptic ulcer - Pain onset after meals. Pain is in umbilical region rather than epigastric. Not relieved by local antacids, but relief with H2 blockers or Omeprazole.
• Meckel's diverticulitis - Leads to oedema, inflammation, gangrene, perforation. Presents exactly like appendicitis, or salpingitis.
• Intussusception - Apex of the intussusception formed by hyperplastic epithelium of the Meckel's presents as acute intestinal obstruction.
• Intestinal obstruction - Either as an internal hernia caused by the fibrous band or volvulus with the fibrous band as the axis.
• "Hernia of Littre" cf Litter's hernia - Meckel's in the hernial sac may present as inflamed hernia, usually on the right
• May present as carcinoid tumor in the Meckel's diverticulum.

Diagnosis

• Often completely incidental at laparotomy
• Technetium scan (99mTc) is performed. 50% have ectopic gastric/pancreatic mucosa and it is this that is highlighted by the scan distant from the stomach.
• Most sensitive radiological investigation is small enema

Differential Diagnosis

• Acute appendicitis
• Acute salpingitis
• Peptic ulcer - DU or GU (may perforate)

Treatment

• If Symptomatic then a resection is required as well treating what ever other pathology exists along side the Meckel's (i.e. hernia reapir / release of small bowel obstruction). The base is often broad and so a resection and end to end anastomosis is advocated, otherwise there is a risk of stricture.
• The treatment of an asymptomatic Meckel's diverticulum is contraversal. Resection involves an anastomosis and so a risk of leak and other complications. There are those that advocate resection in young (under 40) or those with a thickened wall.
• An interesting 2008 Annals of Surgery Paper reviewed a total of 244 papers. They concluded that there was a significantly higher post-op complication rate of Meckel's resection vs those left in-situ and that the long term outcome for patients find to have a Meckel's was of no complications. A NNT analysis revealed that 758 resections would need to be performed to prevent one death from Meckel's diverticulum.
• The important thing to remember is that if you are going to leave an asymtomatic Meckel's in-situ make it clear and in bold in the operative note and ensure you inform the patient plus their GP on discharge.