Symptomatic Parapelvic Cysts in Children: Anatomical and Histological Features, Diagnostic Pitfalls and Urological Management.

BACKGROUND: Symptomatic parapelvic cysts (PPC) are rare entities. Our objective is to highlight specific features of PPC to avoid a misdiagnosis of UPJ obstruction. METHODS: We retrospectively reviewed the records of children managed between 2012-2017. RESULTS: All four patients (18 months-8 years) presented with acute renal colic with a large intra-sinusal liquid mass (42-85 mm) on ultrasound, evoking a diagnosis of UPJ obstruction. On preoperative renal scintigraphy (n = 3) there was no dilatation of the renal pelvis and ipsilateral differential function was impaired in 2. Diagnosis of PPC was suspected preoperatively in three children (CT scan (n = 1); MRI (n = 2)) and made peri-operatively (n = 1). Preoperative retrograde pyelography (n = 3) and a further intraoperative retrograde pyelography with methylene blue (n = 1) did not identify communication with the cyst. No renal pelvis was identified in two patients. De-roofing of the cyst was curative in all cases at 5 years mean follow-up (no leakage, cyst recurrence or loss of function) and all 4 patients became asymptomatic after surgery. Histology demonstrated a single flat epithelial cell layer. Renal function normalized in one patient but remained impaired in the other. CONCLUSION: In case of symptoms of UPJ obstruction with a medial renal liquid mass on ultrasound, PPC should be considered when no dilatated pelvis on renal scan is identified. In such cases, a complementary imaging work-up is mandatory prior to surgery.