Anonymous GA Subscriber
Answer: You could bill the diagnostic laparoscopy (56300) with a -51 modifier (multiple procedures), but the chances are good that the procedure will be denied because the surgery was converted to an open one and many payers will only consider paying for the most extensive procedure.
Your real options in this case, however are either to add modifiers -59 (distinct procedure) and -51 to the 56300 code or to bill the open procedure with a modifier -22 (unusual procedural services) because of the need to perform more work. Check with your carrier to see which method they would prefer.