Incidental Detection of Pseudomembranous Colitis Through 18F-FDG PET/CT During the Restaging of Colorectal Cancer.

A 59-year-old man, previously submitted to anterior resection due to rectal cancer, underwent a contrast-enhanced computed tomography (ce-CT) for restaging before eventual chemotherapy. Because ce-CT showed a moderate enlargement of the descending colonic lumen, in despite the lack of symptoms, positron emission tomography (PET)/CT 18F-fluorodeoxyglucose (FDG) was carried out. 18F-FDG PET/CT demonstrated highly increased tracer incorporation along the colon walls. Two days after the PET/CT examination, complaints of diarrhea and abdominal pain began. Clostridioides difficile stool test resulted positiv; thus, thus he started antibiotic therapy without benefit. Because follow-up ce-CT demonstrated a megacolon condition, he was submitted to hemicolectomy. Histology revealed a diffuse condition of pseudomembranous colitis (PMC). This case highlights the potential of 18F-FDG PET/CT for detecting PMC morphological and functional features also in pre-symptomatic patients.