Bilateral parapelvic cysts that mimic hydronephrosis in two imaging modalities: a case report.

Parapelvic cysts are uncommon conditions that are usually found during autopsy. Their ultrasonographic appearance is similar to hydronephrosis. We report the case of a 46-year-old female with a 4-year history of vague flank pain and a previous history of bilateral moderate hydronephrosis. The patient was investigated by ultrasonography and non-enhanced CT scan, and finally diagnosed as bilateral parapelvic cysts by a contrast-enhanced CT scan. For any patient with hydronephrosis detected by sonography, the possibility of parapelvic cysts should be kept in mind, especially if no underlying cause is detected and other routine imaging is inconsistent with hydronephrosis. In such circumstances a CT scan with contrast enhancement should not be refused, and relying on sonographic signs, previously mentioned in literatures, can be misleading.