Objective To investigate CT imaging features of rectal neuroendocrine tumor (RNET) and identify its diagnostic features.

Methods CT imaging data of 21 RNET cases confirmed by endoscopy or surgical pathology were retrospectively analyzed.

Results Of the 21 cases, 8 were typical carcinoid, 3 were atypical carcinoid, and 10 were poorly differentiated neuroendocrine/small cell carcinoma. The lesions in the lumen were soft nodular-like tissue on plain CT with clear margin and homogeneous density. Enhancement rendered the arterial phase evident and the venous phase moderately visible. A total of 18 cases showed growth in the serous membrane and invasion in the fat around the rectum, 16 cases showed lymph node metastasis around the rectum, and 2 cases exhibited liver metastasis.

Conclusions A number of CT imaging features specifically characterized neuroendocrine tumors; however, definitive diagnosis still relies on pathological diagnosis.