Whole body positron emission tomography/computed tomography (PET/CT) was requested for restaging in a 73-year-old male who underwent wedge resection and radiotherapy for lung cancer. While there was no pathological fludeoxyglucose (FDG) uptake at the operation site, in the mediastinal lymph nodes, and in the bilateral surrenal regions, a mass like focal intense FDG uptake was noted in the left inguinal region. The differential diagnosis included a second primary tumor, metastatic lymphadenopathy, strangulated hernia of the bowel, bladder diverticulum or inguinal herniation of the urinary bladder. A delayed PET/CT exam of the pelvic region after filling the bladder was performed. A full bladder could not be achieved despite well hydration, but delayed images showed some expansion of the FDG accumulation at the left inguinal region. On CT and fused images, we got the impression that there was an anatomical connection between the bladder and the hypermetabolic focus. Bladder herniation was considered based on the CT and fused images. Ultrasound examination confirmed the diagnosis. In conclusion, filling the patients' bladder may help to differentiate this benign condition from malignancies.