Ohio Subscriber Answer: A second encounter is not unusual after a percutaneous nephrostolithotomy (50080 or 50081, which both have 90-day global periods).
If the doctor planned this procedure at the time of the initial procedure, you should use 50551 (Renal endoscopy through established nephrostomy or pyelostomy, with or without irrigation, installation or ureteropyelography, exclusive of radiologic service) and separate it from the global period with modifier -58 (Staged or related procedure or service by the same physician during the postoperative period).
If the doctor did not anticipate this second encounter, however, you should consider modifier -78 (Return to the operating room for a related procedure during the postoperative period). Since the doctor also exchanged nephrostomy tubes, you should also consider reporting code 50398 (Change of nephrostomy or pyelostomy tube) and append modifier -58 to indicate to the carrier that this is a separate, staged procedure that should be paid for even though it occurred during the global surgical period.
If the doctor is planning another endoscopy for next week through the same access, then report 50551 -- or, if necessary, report 50561 (Renal endoscopy through established nephrostomy or pyelostomy, with or without irrigation, installation or ureteropyelography, exclusive of radiologic service; with removal of foreign body or calculus). But if during next week's visit the urologist only removes the catheter, you should not report it separately during the global period.