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

Abstract

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.

White-blue pyelocalyceal cyst with hydrotic glomerulonephritis

“…A parapelvic cyst or a renal sinus cyst of lymphatic origin, arising in proximity to the pelvis and major calyces, can cause diagnostic confusion 7. The parapelvic cyst does not communicate and presents separately with the collecting system, in contrast to the white-blue pyelocalyceal cyst.…”

Renal Cystic Disease

“…On renal ultrasound, hydronephrosis has a similar appearance to that of a parapelvic cyst [ 7 ]. A careful search for depicting a communication between a dilated renal pelvis and dilated renal calyces could support the diagnosis of hydronephrosis.…”

“…On ultrasound, a renal parapelvic cyst appears as an echoic lesion located in the high echogenic renal sinus. If a renal parapelvic cyst has a large size, hydronephrosis could be falsely impressed [ 7 ]. On intravenous urography or retrograde pyelography, the renal pelvis could be opacifi ed by contrast medium which could be thus separated from the parapelvic cyst.…”

Preliminary study on the differentiation between parapelvic cyst and hydronephrosis with non-calculous using only pre-contrast dual-energy spectral CT scans

“…The parapelvic cyst is a rare disease in the clinic with a detection rate in autopsy of about 1.25-1.5%. 1 It is believed to originate from the secondary lymphatic obstruction, 2 and most of the patients were occasionally found without any symptoms. 3 However, when the cyst is large enough, it may lead to hypertension, haematuria, hydronephrosis or secondary infection, and even acute renal failure.…”