MECKEL'S DIVERTICULUM


DEFINITION
A congenital abnormality in which a functionless remainder of an embryonic gut duct persist into adult life, possibly causing problems of infection, obstruction, or abnormal secretion into the bowel.

Rules of 2
-  located~ 2 feet from the ileocaecal valve
- 1 in 2 contains 1 of 2 types of heterotopic tissue gastric /  pancreatic
- 2x more common in males
- 2% of population
- 2% become symptomatic
- usually within first 2 years of life
- 2 inches in length
- 2 predominant symptoms: bleeding and obstruction
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INCIDENCE
Congenitally ~2% of people.
M>F 3-5:1.
Symptoms rare after age 10.
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AETIOLOGY

Congenital

Failure of involution of the vitelline duct (connects lumen of developing gut to yolk sac).

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BIOLOGICAL BEHAVIOUR

Anatomy

An ileal diverticulum, typically around 5 cm long, wide mouthed, contains ileal layers and often heterotopic pancreas or gastric mucosa (in 50%).
Arises from the antimesenteric border of the ileum, typically 40-50 cm from the ileocecal valve (usually less than 100 cm).
May be connected to umbilicus by a fibrous cord or even fistula.

Pathophysiology

Causes illness in three  ways:

1. Secreting potent enzymes - 50% may contain mucosa capable of doing this: ie. gastric (75%) or pancreatic (15%) acid/enzymes
- symptoms decrease post-vomiting and come on worse at night when stomach empty & secreting ongoing, or when hungry.
- bleeding is a predominant symptom; typically along the mesenteric border of the ileum a short way distal to the lesion
- this is the most common Meckel-related problem, overall

2. Becoming infected
- routinely indistinguishable from appendicitis

3. Intussuscepting into ileum and obstructing it; possibly necrosis and perforation.
- obstruction is most common presentation in adults

Natural History
Lifetime risk of asymptomatic Meckel's is very low
Most will become symptomatic in first 2 years of life, certainly by age 18

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MANIFESTATIONS

Symptoms

Local
Secreting
Acid - bleeding most important sign: haematemesis, melaena, anaemia.
Also pain in central abdomen, weight loss.

Infection
Mimics appendicitis.
Infrequently may perforate, with peritonitis.

Obstructed

Symptoms of bowel obstruction.

Signs

As per complication.

Palpate

May be periumbilical tender mass.
Perhaps bowel dilated proximally, if obstruction.

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INVESTIGATIONS

CT
May be visible with contrast.

Angiography

May be located when looking for a bleeding source
May demonstrate a persistent right vitelline artery, arising from the SMA,
- or an embryonic ileal artery branching to it.

Isotope scanning
After technetium injection (Tc99 pertechnetate; taken up by ectopic gastric mucosa).
False positive and false negative results possible.
- depends on skill of radiologist
- may need oblique, lateral or postvoid fills; secretion should occur at same time as stomach
Sensitivity ~80% but can be increased by pre-test pentagastrin or glucagon administration.



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MANAGEMENT

Asymptomatic
Leave it alone
Incidentally discovered Meckel's in adults should be be left alone as the risk of resection probably outweighs the risk of leaving it alone.
- they should be removed only in young children.
But there are relative indications
- palpable evidence of a mass or ectopic tissue
- evidence of prior diverticulitis
- past unexplained GI haemorrhage or abdo symptoms
- mesodiverticular band

Bleeding
Note that bleeding ulcer source is often on mesenteric side of bowel under the Meckel, or on the antimesenteric side just distal to it.
Amputation or wedge resection is not enough.
Explore and conduct a small bowel resection.

Infection
Depending on degree of inflammation.
1. Small bowel resection may be most appropriate
2. Else simple stapled amputation or wedge resection of the Meckel.
- pick up Meckels with two babckocks
- lay across an nTLC 75, longitudinally along the bowel, ensure there is not going to be any narrowing
- fire.

Obstruction
Relieve then resect by wedge resection or amputation.


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