Massachusetts Subscriber
Answer: You are right to use modifier 53 (Discontinued procedure). You should submit CPT 53850 (Transurethral destruction of prostate tissue; by microwave thermotherapy) and append modifier 53 to indicate that your physician had to terminate the procedure before he was able to complete it.
Many carriers remove the global-period restrictions on a procedure if you append modifier 53. Therefore, when the patient undergoes surgery again so that your urologist can finish the procedure, you can once again report 53850.
Tip: If you submit claims to a carrier that will not remove the global period when you use modifier 53, you should still report the second surgery using 53850 but you should attach modifier 58 (Staged or related procedure or service by the same physician during the postoperative period). The urologist should clearly document in the patient's medical records that the subsequent surgery is the second stage of a now completed procedure.
The diagnosis code you should use would most likely be 600.01 (Hypertrophy [benign] of prostate with urinary obstruction).