Parapelvic Cysts of the Kidney

Parapelvic cysts of the kidneys are simple renal cysts, which are adjacent to the renal pelvis or the renal sinus.The parapelvic renal cyst is a relatively common finding on routine urological examination, but only rarely needs treatment.

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.

Unlike simple renal cysts, they do not lie within the renal parenchyma.They are located on, or probably originate in, the hilus of the kidney in close proximity to the pelvis and major calyces.They are thought to be lymphatic in origin and may be congenital.Their appearance in an intravenous urogram (IVU) is similar to that of renal sinus lipomatosis and in sonography it is similar to hydronephrosis.Some signs have previously been described to help differentiate these cysts from hydronephrosis in ultrasound imaging.We present a case of bilateral parapelvic cysts in which conventional sonographic criteria could not help to make diagnosis.

Parapelvic cysts may also derive from the renal parenchyma adjacent to the renal pelvis.Normally, there are no complaints.Parapelvic cysts can compress the pyelocaliceal system or ureter , cause flank pain or lead to other symptoms of urinary obstruction.

Typical parapelvic cysts are multiple and most probable derive from lymphatic vessels, often associated with nephrolithiasis or urinary obstruction.

Renal ultrasound should be sufficient for the diagnosis; in doubtful situations an intravenous pyelography, CT Abdomen or renal scintigraphy can rule out urinary obstruction.