GI Radiography

Imaging Diagnosis:

Sigmoid volvulus with “whirl sign”

Discussion:

Volvulus is a torsion of the bowel about its own mesentery resulting in a closed loop obstruction.

CT is usually the imaging modality of choice in patients presenting with acute abdominal pain. Furthermore, the diagnosis may be obscured on plain abdominal films because the closed loop obstruction is filled with fluid, orientated in an anteroposterior plane, or obscured by overlapping loops of air distended bowel. CT detects the presence and location of the volvulus with the added benefit of identifying potential fatal complications such as ischemia and perforation. Three-dimensional reconstructions may further improve diagnostic capabilities by allowing visualization of the entire bowel in a
single image.

A specific CT sign for volvulus is known as "the whirl". This has been described in volvulus of the midgut, cecum and sigmoid colon. The whirl is composed of spiraled loops of collapsed large bowel. Low attenuation fatty mesentery with enhancing engorged vessels radiate from the twisted bowel. In the central eye of the whirl, a soft tissue density pinpoints the source of the twist.

Treatment
Colonoscopy has been shown to have a high rate of diagnosis and reduction in
cases of sigmoid volvulus, but is often not ideal in treating volvulus of the cecum. Reduction rates by colonoscopy are much lower in treating cecal volvulus and there is a recurrence rate of greater than 50%. In cases of uncomplicated cecal volvulus, surgical options include cecopexy which has a low rate of morbidity (0-8%) and volvulus recurrence. Gangrene or perforation requires surgical resection which eliminates the possibility of recurrence and also has a low morbidity and mortality. CT findings change patient management by the demonstration of the signs of bowel ischemia which include
thickening of bowel wall, mesenteric hemorrhage and pneumatosis intestinalis

Contribution
Dr Russell Pinto, Mumbai