Retained nephrostomy thread providing a nidus for atypical renal calcification.

Percutaneous nephrostomy (PCN) is a commonly performed procedure. The indications have expanded from merely providing emergency decompression of obstruction to being the initial step of many interventional procedures including percutaneous nephrolithotomy, ureteral stenting dilation and biopsy. Nephrostomy tube design has evolved from a simple trocar to the current self-retaining loop catheters. These catheters contain a suture which, when secured, locks the loop of the catheter in order to prevent accidental removal of the catheter. We present a case where incomplete removal of the locking suture providing the nidus for calcification within the renal pelvis.