Sigmoid volvulus

Sigmoid volvulus occurs when a long, redundant sigmoid loop twists around its mesenteric axis. It is most common in elderly, institutionalised or chronically constipated patients and in those with neuropsychiatric conditions.

Clinical presentation

Abdominal distension, colicky pain and absolute constipation, often developing over a day or two. Peritonism, fever or shock suggest ischaemia or perforation.

Radiographic features

Abdominal radiograph

• A massively dilated, inverted U-shaped loop of colon rising out of the pelvis — the coffee bean sign
• Absence of haustra in the twisted loop
• The apex often lies under the left hemidiaphragm, above the level of T10
• Proximal large bowel dilatation

CT

Shows the whirl sign of the twisted mesentery, two points of transition (closed loop) and complications such as ischaemia or perforation.

Treatment and prognosis

Without signs of ischaemia, endoscopic decompression with a flatus tube is first-line. Recurrence is common, so elective sigmoid resection is often advised once the patient is fit. Ischaemia or perforation require emergency surgery.

Differential diagnosis

• Caecal volvulus (dilated loop points to the left upper quadrant)
• Colonic pseudo-obstruction
• Large bowel obstruction from a tumour