Our standard operative protocol for PNL as described next will be followed for all cases. After receiving a general anaesthetic, cystoscopy and placement of a ureteral catheter on the affected side may be performed. The will be used to perform retrograde pyelography in order to determine the optimal access site to the kidney. A Foley catheter will be placed to drain the bladder throughout the procedure. Next, under fluoroscopic guidance, access to the affected renal collecting system will be obtained with a needle down which a guide wire is passed by the interventional radiology department or the operating surgeon.