(18)F-FDG PET/CT findings of obstructive colitis proximal to colorectal cancer

This study was performed to determine the frequency and patterns of obstructive colitis (OC) seen on F-FDG PET/CT scan of patients with adenocarcinoma of the colon and rectum.

Preoperative PET/CT scans and surgical records of 308 patients with surgically proven colorectal adenocarcinoma were retrospectively reviewed for the presence of colon obstruction and OC proximal to the colorectal adenocarcinoma. The distributions, patterns, and SUVmax of OC were evaluated on PET/CT. Abdominal CT, colonoscopic finding, and histopathologic findings of surgical specimen were also reviewed.

Of 308 patients, PET/CT scans of 29 (9.4%) showed OC. The mean SUVmax of OC was 3.6 ± 2.2 (range, 1.6-12.3). Obstructive colitis was contiguous to the tumor in 23 patients (79.3%) and noncontiguous in 6 (20.7%). Obstructive colitis was diffuse in 25 patients (86%) and patchy in 4 (14%). It was segmental in 16 patients (55%) and pancolonic in 13 (45%). Twenty-three of 29 patients (79.3%) showed proximal wall thickening to colon cancer on abdominal CT performed about 3 days before PET/CT.The patients with OC on PET/CT was significantly associated with annular (P = 0.017), large-sized (P < 0.001), and advanced colon cancer (P < 0.001). However, there was no association between tumor size and SUVmax of OC.Ten proximal polyps were detected in 7 of 29 patients (24.1%) on colonoscopy and surgical specimen. Of these, 1 proximal polyp was removed before PET/CT scan, whereas the remaining 9 were not detected on PET/CT scan.

Obstructive colitis is predominantly diffuse and contiguous with the obstructing adenocarcinoma. Colorectal cancer with OC tends to show annular shape and larger tumor size. Obstructive colitis may lower the possibility of detection of synchronous proximal colonic lesion by PET/CT.