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Zebra spleen and liver

Alternating bands of high and low attenuation on CT have been described as a zebra pattern due to the similarities with a zebra’s stripes. This is a normal finding on the arterial phase CT of the spleen and is thought to be due to the histology of the spleen which has alternating cords of red and white pulp which enhance at different rates. The peak visualisation of heterogeneous enhancement occurs 27 seconds after injection and splenic enhancement typically becomes homogeneous by 70 seconds after injection. This pattern has also been described as a serpentine or arciform pattern of enhancement. The phenomenon is also seen on MRI and ultrasound of the spleen. A zebra pattern of enhancement can also be seen in the liver in CT arterial portography (CT obtained with direct contrast injections via an arterial catheter into either the superior mesenteric artery or splenic artery). The mechanism for the variegated pattern is thought to be due to non-uniformly mixed blood and contrast causing variable enhancement throughout the liver. It has been shown that the larger the size of the spleen, the lower the chance of a zebra pattern of enhancement in the liver following splenic artery injection due to a relatively larger volume of opacified splenic vein blood mixing with nonopacified superior mesenteric vein blood. Related sign