Sigmoid volvulus

A 75-year-old man with sigmoid volvulus.
(A) Drawing shows split-wall sign caused by apparent separation of sigmoid walls by adjacent mesenteric fat (arrow) secondary to incomplete twisting. Horizontal lines and schematic axial insets indicate levels of B-D.
(B) Contrast-enhanced axial computed tomography (CT) image through the single beak-shaped transition point (arrow).
(C) Axial CT image 25 mm caudal to B shows mesenteric fat (arrow) separating the two sigmoid walls (arrowheads).
(D) Axial CT image 25 mm caudal to C shows the decompressed rectosigmoid (arrow).