The bowel wall target sign.
Abdom Imaging. 2015 Feb;40(2):457-8. doi: 10.1007/s00261-014-0261-3.
Walter J1, Ayoob A, DiSantis D.
Traditionally, a target configuration describes concentric circles [1]. So when CT depicts abnormally thickened bowel wall as concentric rings of varying attenuation, the imaging appearance has been dubbed the target sign (Fig. 1) [2].
On intravenous contrast enhanced CT without positive enteric contrast material (Fig. 2 a, b), the target sign comprises three rings of alternating attenuation. Two high attenuation value rings—mucosa (inner ring) and muscularis propria (outer ring)—are separated by low attenuation value submucosa (middle ring), presumably reflecting edema or fat [3, 4].