Whirl sign — a hurricane on a weather map

An 82-year-old man presented to the emergency department with abdominal pain and vomiting. An abdominal computed tomography scan showed a whirl sign around the superior mesenteric vessels (Figure, arrow), suggestive of small bowel volvulus. A whirl is formed by the afferent and efferent loops of the volvulus, with the central portion consisting of tightly twisted bowel and mesentery.1 The latter create swirling strands of soft tissue shadow within a background of mesenteric fat attenuation, giving the appearance of a hurricane on a weather map. Caecal and sigmoid volvulus can also give rise to whirl signs. Laparotomy confirmed mid-gut volvulus with 360° rotation. The patient had an uneventful recovery following derotation of the mesentery.