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Case 47

Sigmoid volvulus

A woman with increasing abdominal pain and distension

Ed Kalkman

This 62 year old woman presented to the emergency department with one week's history of increasing abdominal pain and distension. She gave a long history of chronic constipation, but was otherwise fit and well.

A plain abdominal film was obtained. What does it show, and how could you confirm this?

On the plain film the entire colon is dilated with faeces and air. In particular, there is an inverted "U-shaped" loop projected over the pelvis and lower abdomen.

We chose to perform a water-soluble contrast enema.

Findings

Contrast failed to progress beyond the recto-sigmoid junction. At this point, there is smooth, curved tapering like a bird's beak ("bird of prey sign").

Diagnosis

Sigmoid volvulus

Discussion

Sigmoid volvulus is said to occur with increased incidence in very old or debilitated patients (our patient was not in this category). It results from twisting of the sigmoid loop around its mesentery. It is usually chronic, with intermittent acute attacks.

The following findings are common on plain radiographs: An "inverted U" shaped loop, commonly without haustration, often overlapping the liver (liver overlap sign), the dilated descending colon (left flank overlap sign) and the left side of the pelvis (pelvic overlap sign). The top of the volvulus can be as high as T10, the apex is usually seen left of the midline. Often, an inferior convergence of 3 white lines is demonstrated at the left side of the pelvis. The ratio of air to fluid is usually greater than 2:1.

At contrast examinations, the following findings can be made: Smooth, curved tapering at the area of torsion, resembling a bird of prey. Sometimes, the mucosal folds are arranged in a screw configuration. In chronic volvulus, mucosal thickening at the twist may result in shouldering of the narrowing.

The diagnosis of sigmoid volvulus in our patient was confirmed at surgery.

References

Grainger & Allison's Diagnostic Radiology, Third Edition, p894.

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