Periportal low-attenuation areas on CT: value as evidence of liver transplant rejection

CT scans of liver transplants may show periportal areas that are lower in attenuation than adjacent portal veins and liver. These areas appear as low-density rims that surround or parallel the portal vein and its intrahepatic branches as well as the immediate subhepatic portal area. In order to determine the value of periportal low attenuation as an indicator of rejection, we reviewed the CT scans of 37 liver transplant patients with biopsy evidence of either acute rejection (12 patients) or nonspecific change without rejection (25 patients). Low-attenuation areas around peripheral portal branches were identified in six of 12 patients with rejection and in four of 25 patients with nonspecific change (sensitivity, 50%; specificity, 84%; accuracy, 73%). The correlation between peripheral periportal low attenuation and rejection was statistically significant (p less than .05). Periportal low attenuation in a central location was seen in eight of 12 patients with acute rejection and in 14 of 25 patients with nonspecific change (sensitivity, 67%; specificity, 44%; accuracy, 51%). The correlation was not statistically significant. Low-attenuation areas were evident on scans obtained either with or without IV contrast enhancement. Periportal low-attenuation areas are commonly seen on CT scans of liver transplants. Peripheral areas correlate with acute rejection, but other factors probably contribute to their occurrence. Central areas do not correlate with acute rejection. Low sensitivity and relatively low accuracy limit the usefulness of peripheral periportal low attenuation as a sign of acute liver allograft rejection.