Objective: To conclude features of combined positron emission tomography (PET) and computed tomography (CT) in detection of pelvic recurrence in patients with rectal cancer who underwent abdominoperineal or anterior resection.Methods: Eighteen patients with suspected recurrent rectal cancer were enrolled; 10 were men, and 8 were women.The mean age was 58(range: 38-79).The time of afteroperation ranged from three months to seven years.The patients fasted at least 6 hours prior to intravenous injection of 18F-FDG (3.7MBq/kg).Scanning from the base of the skull through the midthigh was performed with the Philips Gimini TF.Two readers interpreted images in consensus.Pelvic recurrence was confirmed with histologic analysis or clinical and imaging follow-up.RESULTS: There were 25 pelvic sites detected.22 were malignant and the other three were benign.The recurrent sites were all with increased 18F-FDG-uptake,and the maximal standardized uptake value(SUVmax) was 5.63±1.90.On the other hand,the benign lesions had lower uptake and SUVmax was 2.0±0.79.Its obvious the difference of 18F-FDG-uptake between malignant and benign lesions.Most recurrence sites located in the surrounding tissues ,presacral region and perineum.The 18F-FDG-uptake of recurrence was ofen focal and intense.CONCLUSIONS:It was reported that the local recurrence rate after resection of rectal carcinoma was above 30%.In patients with suspected recurrent rectal cancer,18F-FDG PET/CT has been found to be especially useful not only for differentiating between disease recurrence and postoperative scarring,but also for detecting recurrence at unexpected sites.