Peritoneal Actinomycosis After Bariatric Surgery Mimicking a Peritoneal Carcinomatosis on 18 F-FDG PET/CT.

A 54-year-old man with a history of bypass surgery 3 years ago presented with ascites, abdominal pain, and a decline in general health. CT and 18 F-FDG PET/CT suggested peritoneal carcinomatosis, but histology revealed peritoneal actinomycosis. This rare peritoneal infection can occur after digestive surgeries, such as bariatric procedures, due to disruption of the digestive barrier, allowing actinomycosis to spread outside its typical anatomical location. Clinicians should consider this diagnosis after bariatric surgery, even years later, especially in the absence of neoplastic disease.