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Sigmoid volvulus

Sigmoid volvulus is a cause of large bowel obstruction and occurs when the sigmoid colon tortes on the sigmoid mesocolon.

Epidemiology

Large bowel volvulus accounts for ~5% of all large bowel obstructions, with ~60% of intestinal volvulus involving the sigmoid colon 6. It is more common in the elderly 7.

Clinical presentation

Symptoms are that of a large bowel obstruction - constipation, abdominal bloating, nausea and/or vomiting. Onset may be acute or chronic. 

Pathology

Aetiology

There is a wide range of causes, some are region-specific 5:

  • chronic constipation and/or laxative abuse
  • fibre-rich diet (especially in Africa)
  • Chagas disease (especially in South America)
Associations

Radiographic features

Sigmoid volvulus is differentiated from a caecal volvulus by its ahaustral wall and the lower end pointing to pelvis

Plain film

Abdominal radiographs will demonstrated a large, dilated loop of colon, often with a few air-fluid levels. Specific signs include:

Fluoroscopy

Although now uncommonly performed, a water soluble contrast enema exquisitely demonstrates this condition, with the appearances described as the bird of prey sign.

CT

Treatment and prognosis

Rectal tube insertion is successful in successful in treating 90% of cases 5. Mortality rate is 20-25% 7. The most serious complication is bowel ischaemia.

Differential diagnosis

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