BACKGROUND/AIMS: Incidentally detected focal 18F-fluorodeoxyglucose (FDG) uptake was compared with colonoscopy. We investigated the characteristics of colon adenomas which were revealed on PET/CT. Then we identified whether additional colonoscopy was necessary in patients with lesions which were revealed on PET/CT but had no matched lesions on colonoscopy. METHODS: We retrospectively reviewed 95 patients who underwent colonoscopy within a 6 month interval after they had focal FDG uptake from January 2010 to May 2012 at National Police Hospital in Korea. Also, we analyzed 30 patients who underwent additional colonoscopy within 2 years after they had no matched lesions on primary colonoscopy. RESULTS: PET/CT depicted 54.6% (41/75) of adenomas and adenocarcinomas. The PET visibility of colon adenoma was significantly associated with degree of dysplasia (p=0.027), histologic type (p=0.040), and the size (p=0.038). The positivity rate was increased with higher degree of dysplasia (low-grade dysplasia, 47%; high-grade dysplasia, 78%; adenocarcinoma, 100%) and villous patterns of histologic type (tubular, 46.8%; tubulovillous, 87.5%; villous, 100%). Patients with adenomas larger than 10 mm (87.5%) had higher detection rate compared to those with adenomas smaller than 10 mm (49.0%). Among the 30 patients who underwent additional colonoscopy, only one patient had a 6 mm sized tubular adenoma (low-grade dysplasia). CONCLUSIONS: Incidental focal colonic uptake may indicate advanced adenoma or adenocarcinoma. Thus, it justifies performing colonoscopy for identifying the presence of colon neoplasms. However, in case of unmatched lesions between PET/CT and colonoscopy, there was little evidence that additional colonoscopy would yield benefits.
Adenocarcinoma/pathology/radiography/radionuclide imaging ; Adenoma/pathology/radiography/radionuclide imaging ; Adult ; Aged ; Colonic Neoplasms/pathology/*radiography/*radionuclide imaging ; Colonic Polyps/pathology ; Colonoscopy ; Female ; Fluorodeoxyglucose F18/diagnostic use ; Humans ; Male ; Middle Aged ; Multimodal Imaging ; Positron-Emission Tomography ; Radiopharmaceuticals/diagnostic use ; Retrospective Studies ; Tomography, X-Ray Computed

A 70-year-old man with past history of hemicolectomy due to colon cancer underwent a follow-up abdominal/pelvic CT scan. CT revealed a right adrenal metastasis and then he underwent FDG-PET/CT study to search for other possible tumor recurrence. In PET images, other than right adrenal gland, there was an unexpected intense FDG uptake at right inguinal region and at first, it was considered to be an inguinal metastasis. However, correlation of PET images to concurrent CT data revealed it to be a bladder herniation. This case provides an example that analysis of PET images without corresponding CT images can lead to an insufficient interpretation or false positive diagnosis. Hence, radiologists should be aware of the importance of a combined analysis of PET and CT data in the interpretation of integrated PET/CT and rare but intriguing conditions, such as bladder herniation, during the evaluation of PET scans in colon cancer patients.
Abdominal Neoplasms/radionuclide imaging/secondary ; Aged ; Colonic Neoplasms/pathology/radiography/radionuclide imaging ; Diagnosis, Differential ; False Positive Reactions ; Fluorodeoxyglucose F18/*diagnostic use ; Hernia, Inguinal/radiography/*radionuclide imaging ; Humans ; Male ; *Positron-Emission Tomography ; Radiopharmaceuticals/*diagnostic use ; Tomography, X-Ray Computed ; Urinary Bladder Diseases/radiography/*radionuclide imaging