This case provides an excellent example of a massive sigmoid volvulus with classic imaging findings.

A sigmoid volvulus arises in the pelvis from the left lower quadrant, often with a "coffee-bean" sign present. Because the sigmoid colon rotates around its mesentery, this creates a whirling pattern of the vessels at the base of the mesentery. This can be appreciated on the CT coronal reformats (whirl or whirlpool sign). 

As the large bowel obstruction is rather distal, there is dilatation of the descending, transverse and ascending colon, creating a closed-loop obstruction at the ileocecal valve. The large bowel loops dilate up toward the right upper quadrant and there are usually very few air-fluid levels. 

In comparison, a cecal volvulus arises in the right lower quadrant and the dilated bowel extends toward the left upper quadrant. The distal large bowel collapses whilst the small bowel becomes distended. This is often associated with many air-fluid levels. 

This patient had 48 hours of symptoms prior to presentation and, due to obstructed blood flow through the sigmoid mesentery, had ischemic bowel that was not viable and required resection.