The Ring Sign

The ring sign is seen on transverse computed tomographic (CT) scans of the abdomen or pelvis. The characteristic features of the sign are a round or oval pericolonic lesion with attenuation that is either the same as or higher than that of normal peritoneal fat and a thickened hyperattenuating rim that represents the ring.

Transverse contrast material–enhanced CT scan of patient presenting with abdominal pain. Scan demonstrates thickening of visceral peritoneum (arrow) around epiploic appendage of sigmoid colon.                       

Transverse contrast-enhanced CT scan of patient presenting with abdominal pain. Scan demonstrates thickening of visceral peritoneum around epiploic appendage (arrow) of sigmoid colon and increased attenuation of fat (∗) resulting from edema, inflammation, or hemorrhage.                       

 The ring is caused by the thickening of a rim of visceral peritoneum around the epiploic appendages in the absence of surrounding pathologic abnormalities and can be seen in patients with primary epiploic appendagitis (PEA). A central dot or line of increased attenuation may also be seen and is thought to represent a thrombosed vessel, fibrous tissue, or hemorrhage. Perilesional stranding and fascial thickening, which may be caused by edema or inflammation, are frequently encountered. Mass effect and focal wall thickening of the adjacent colon may also be present. PEA is caused by torsion or spontaneous venous thrombosis, with subsequent ischemic or hemorrhagic infarction of the appendages.