Extrarenal calyces mimicking retroperitoneal cystic mass with concomitant ureteropelvic junction obstruction: renal pelvis reconstruction using calyx unification.

Extrarenal calyces (ERCs) are a very rare urological anomaly, especially when concomitantly presenting with ureteropelvic junction obstruction (UPJO). Surgical intervention is often necessary in ERCs associated with UPJO, with dismembered pyeloplasty being the most commonly utilized technique. We present a case of UPJO-associated ERCs in which renal pelvis reconstruction using calyx unification was selected as the treatment technique. An 11-year-old boy was referred to our center due to bilateral hydronephrosis and left multicystic kidney disease. Magnetic resonance imaging showed severe left hydronephrosis with concomitant left cystic mass and left UPJO. A 99mTc diethylenetriaminepentaacetic diuretic renal scan showed residual renal function of 25.9% split function and 26.8 mL/minute glomerular filtration rate. Intraoperatively, we found ERCs with severely dilated renal pelvis. The renal pelvis was excised. Major calyces protruding from the kidney were unified using side-to-side anastomosis to form a new structure resembling a renal pelvis, which was further anastomosed to the ureter. Temporary urinary drainage from the affected kidney was achieved using a double-J (DJ) stent and nephrostomy. Pathological examination revealed atrophic transitional epithelial cells. There was no intra- or postoperative complication reported. The nephrostomy tube and DJ stent were removed 2 weeks and 3 months after surgery, respectively. Ultrasonography examination performed at 1 and 9 months after DJ-stent removal showed no hydronephrosis. We conclude that renal pelvis reconstruction using calyx unification can be performed safely and is effective in treating patients with ERCs associated with PUJO. This technique should be considered especially in cases where excision of the renal pelvis cannot be avoided.