The hourglass sign.

The Hourglass sign is a useful imaging clue for diagnosing diaphragmatic ruptures with viscera herniation on multidetector CT, with a sensitivity ranging from 16% to 63% and a specificity around 98%-100%. This sign is also commonly found in the literature under the name "Collar sign," first described in 1995 by Worthy et al. It refers to the waistlike constriction of the herniated structure at the site of the diaphragmatic rupture.