A Case of Dental Infection Where Pleural Effusion Was Incidentally Revealed on a CT Scout Image

ABSTRACT Background CT scout images are primarily obtained to determine the imaging field of view; however, lesions or pathological findings may occasionally be identified outside the designated scan area. We report a case of dental infection where pleural effusion was incidentally revealed on a CT scout image. Case Presentation A 57‐year‐old male was referred to our department from a local dental clinic for evaluation of right cheek swelling. Swelling was observed on the right cheek, and the maxillary right first molar exhibited moderate mobility. Contrast‐enhanced CT images revealed an abscess cavity in the cheek, extending from the maxillary right first molar. Blood tests revealed elevated levels of CRP and interleukin‐2 receptor (IL‐2R). Pus was observed upon aspiration due to suspected abscess formation, so an incision and drainage procedure was performed. Regarding the elevated IL‐2R levels, the patient was referred to our hospital's hematology department, where it was diagnosed as being due to inflammatory changes. However, during that consultation, a CT scout scan revealed left‐sided pleural effusion, leading to a referral to the respiratory medicine department on the same day. Thoracentesis was performed, and a subsequent diagnosis confirmed typical pneumonia‐associated pleural effusion caused by a dental infection. The causative tooth, the maxillary right first molar, was extracted in the same month following resolution of inflammation. Pleural effusion improved, and facial swelling resolved. Conclusions Dental infections require caution as they can lead to pulmonary complications such as empyema. Utilizing information incidentally captured in CT scan images can be useful as an aid to diagnosis.