Andrey Yudin

Split Pleura Sign

The split pleura sign (↑) is seen with pleural empyemas and is considered the most reliable CT sign helping to distinguish empyemas from noninfectious pleural effusions. The sign results from fibrin coating of both the parietal and visceral surface of the pleura with resulting ingrowth of blood vessels. Following IV contrast injection CT shows a loculated fluid collection and thickened pleural layers with accompanying enhancement. Both layers of the pleura can then be visualized as linear regions of enhancement that divide around a less dense empyema or in other words come together at the margins of the collection. Do not confuse with subpleural lung consolidation (image right below).

Draped Aorta Sign

The “draped aorta” sign (↑) can indicate a recent rupture of the aorta. This sign manifests itself as a blurred aortic back wall or its wide intimate contact with the contour of the vertebral body. Such signs as “hematocrit,” “sentinel clot,” and “hyperdense crescent” can also be visible.

Double Duct Sign

Simultaneous dilation of the common bile duct and the pancreatic duct – the “double duct” sign (↑) – is extremely suspicious of an ampullary carcinoma (∆). The tumor is well defined after oral administration of water and IV enhancement.

Honeycomb or Spongelike Mass and Spoke-Wheel Sign

Pancreatic serous cystadenoma (serous microcystic adenoma) is a benign tumor which consists of a considerable amount of small cysts (more than 6 and less than 2 cm in diameter), more common in the pancreatic head.

Claw Sign or Beak Sign

In cases when some masses or cysts grow and bulge from renal parenchyma, the normal tissue covers their contours with the formation of acute angles – the “claw” sign or the “beak” sign (↑).

Fat Halo Sign

Fatty infiltration of the submucosal bowel layer – the “fat halo” sign (↑) – can be regarded as specific for inflammatory bowel diseases (Crohn disease, ulcerative colitis), but unlike the “double halo” sign and the “target” sign, it indicates the chronic stage of disease.

White Liver Sign

Excess accumulation of substances with high features of X-ray attenuation can lead to a substantial increase in liver density on native images forming the “white liver” sign (↑). Most often such changes are visible in cirrhosis because of hemosiderin accumulation in regenerative nodes. High density of the liver can also be found in patients receiving amiodarone as a molecule of this substance includes an atom of iodine.

Bat Wing, Butterfly, or Angel Wing Sign

Air-space edema may be diffuse, multifocal, or patchy but mainly bilateral. Symmetrical perihilar ground-glass opacities sparing the cortex of the lungs (known as the “bat wing,” “butterfly,” or “angel wing” sign) may be seen sometimes and attributed to rapid accumulation of edema fluid. Similar pulmonary opacities can be found in patients with pneumonia, inhalation injuries, alveolar proteinosis, pulmonary hemorrhage, sarcoidosis, and bronchoalveolar carcinoma.

Putty Kidney Sign

“Putty kidney” is pronounced calcification (↑) of nonfunctioning kidney parenchyma (autonephrectomy), caused by end-stage tuberculosis.

Signet Ring Sign, Tram-Tracking Sign, String of Pearls, and Cluster of Grapes

These are the signs of bronchiectasia. In true bronchiectasia, the diameter of a bronchial lumen which is perpendicular to the tomogram plane exceeds the diameter of the adjacent pulmonary artery branch (↑) more than 1.5 times (the “signet ring” sign). Parallel walls of the bronchi in cylinder bronchiectasias when visualized in the plane of tomographic image form the “tram-tracking” sign (∆) because there is no normal narrowing of a bronchial lumen to the periphery. Varicose bronchiectasias in the tomographic plane look like a chain or the “string of pearls” (right upper images). The group of cystic bronchiectasias can create a view of the “cluster of grapes” on CT (right lower images).