Purpose : Periportal low attenuation, defined as low attenuation rim around the portal vein and its brancheson contrast material-enhanced CT scans, has been described in a variety of conditions. We tried to document themajor causes of periportal low attenuation in patients with gastric carcinoma after radical surgery. Materials andmethods : The early postoperative CT images of two groups were analyzed and compared. One group(n=9) underwent R2(group 1 and group 2 lymph node) dissection only, while the other(n=9) underwent R2 dissection extended to thehepatoduodenal ligament node. Follow-up CT scans were obtained in five patients with periportal low attenuation at1, 3, 5 months after surgery. In addition, we retrospectively analyzed the 52 cases who underwent gastric surgeryfor gastric carcinoma showing periportal low attenuation at CT. Results : Periportal low attenuation was seen in8(89%) of 9 patients who underwent R2 dissection extended to the hepatoduodenal ligament node, and not seen in 9patients who underwent R2 dissection only. Follow-up CT scan reveals disappearance of periportal low attenuationin 60%, 80%, 100% at 1, 3, 5months respectively. In 32 of 52 cases(62%) periportal low attenuation was reversibleand in 9 of 52 cases(17%) lymphadenopathy in hepatic hilum was the main additional finding. Conclusion : Theextensive lymph node dissection extended to the hepatoduodenal ligament node may be the major cause of periportallow attenuation at CT in patients with gastric carcinoma after surgery, but other factor probably contribute totheir occurance in the later postoperative CT scan, especially such as metastatic lymphadenopathy.