Incidental Detection of Peri-Renal Hemorrhage on F-18 FDG PET/CT Imaging in a Patient with Polycystic Kidney Disease

Hemorrhagic renal cysts are the most frequent complication of patients with PKD [1]. The cause of cyst rupture with hemorrhage is unclear, as it is not known whether expansion with increased intracystic pressure occurs, with the subsequent tearing of blood vessels, or whether hemorrhage into the cyst is the first event, with subsequent rupture from cyst expansion [2]. Bleeding is usually confined within the cyst but occasionally extends into the renal collecting system leading to hematuria or into the perinephric space leading to peri-renal hematoma, or retroperitoneal hemorrhage. Perinephric hematomas have been reported in up to 13% of patients with PKD [3]. Belville suggested that CT scanning is the most valuable examination for patients with spontaneous renal hemorrhage [5]. However, increased FDG uptake in response to hemorrhage has been reported in other soft tissues, including aortic wall hematoma, pelvic hematoma, subarachnoid hemorrhage and adrenal hemorrhage [5, 6]. Although pathophysiology of FDG uptake in hemorrhage remains to be defined, the FDG uptake in hematoma is due to the extravasation of activated macrophages [7]. In the present case, the FDG-PET/CT scan was useful to diagnose an unexpected renal hemorrhage in a patient with PKD