Presentation
Abdominal pain and constipation for 2 days
Patient Data
Dilated large bowel loops with air-fluid levels, the maximum diameter of 7 cm at descending colon with abrupt cut off at the sigmoid colon with a change in caliber and twist of sigmoid colon mesentery with indentation of pericolic fat into the wall of the bowel (partial twist). Wall enhancement is normal. Minimal ascites.
Rectum, distal sigmoid and small bowel loops appear normal.
Posterior interposition of the hepatic flexure to the liver seen reaching to the under-surface of right hemidiaphragm.
Note small duodenal diverticulum and prostatomegaly.
Arrows point to the site of sigmoid mesentery twist.
Laparotomy showing gangrene of sigmoid colon.
Case Discussion
Sigmoid is a common site for colonic volvulus.
Abdominal radiograph can give enough information and the following pointers can favor the diagnosis of sigmoid volvulus:
- disproportionate sigmoid colon enlargement compared to the rest of the bowel
- distended sigmoid colon with an inverted U shape appearance
- coffee bean sign - Coalescence of the medial walls of the ascending and descending sigmoid loops
- location of the apex of the distended loop
- liver overlap sign
- extension of the sigmoid to the left hemidiaphragm
- cephalad position of the sigmoid colon relative to the transverse colon (northern exposure sign)
- proximal colonic dilatation
- absence of rectal gas
In cases where the diagnosis is uncertain on radiography, CT is useful in revealing the abnormal position and swirling of the mesentery with help of coronal and sagittal reformations.
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