Incidental detection of pseudomembranous colitis through 18F-FDG PET/CT during restaging of colorectal Cancer

A 59-year-old man, previously submitted to anterior resection due to rectal cancer, underwent a contrast enhanced CT (ce-CT) for restaging before eventual chemotherapy. Since ce-CT showed a moderate enlargement of descending colonic lumen, in spite of lack of symptoms, a positron emission computed tomography (PET/CT) with 18F-fluorodeoxyglucose (18F-FDG) was carried out. 18F-FDG PET/CT demonstrated highly increased tracer incorporation along colon walls. Two days after the PET/CT examination, complaints of diarrhea and abdominal pain began. Clostridioides difficile stool test resulted positive, thus he started antibiotic therapy without benefit. Since 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 the detection of PMC morphological and functional features also in pre-symptomatic patients.