Retroperitoneal Fibrosis Detected on FDG PET/CT Imaging
A 51 year old male presented with lower left back pain radiating to his groin and pelvis. MRI and CT demonstrated a mass of soft tissue surrounding the aorta and left side of the IVC and suggested that it consisted of a mantle of lymph nodes, possibly secondary to lymphoma, but could not exclude other neoplastic conditions or retroperitoneal fibrosis. A CT guided biopsy showed active inflammation, fibrous tissue and cells of a lymphoid nature, but an unequivocal diagnosis was not possible. A whole body PET/CT scan was performed with the patient fasted and hydrated. 300MBq of FDG was injected 60min prior to the scan. After voiding, the patient was scanned from upper thighs to the base of the skull using a Philips Gemini 16 PET/CT scanner. The scan showed a retroperitoneal FDG avid mass with SUV of 3.5 and no other abnormal uptake. The abnormal activity suggested that the mass was more likely to be retroperitoneal fibrosis rather than lymphoma due to the relatively low SUV and less lobular appearance of the mass and no other abnormalities. An open surgical biopsy subsequently showed fibrofatty connective tissue with dense inflammatory cell infiltrate. It found no evidence to suggest that the mass was lymphoma or any other malignant process and suggested the mass was related to retroperitoneal fibrosis. Other reports of PET in retroperitoneal fibrosis have shown similar findings to this case.