We are an ASC and we bill bilateral pain injections using two identical CPT codes with LT/RT modifiers. This is what our third party coding company has done for awhile, and payers have no issues. We recently had a dispute with someone saying we should be coding the CPT code with modifier 50. Does anyone have a source that says LT/RT modifier use instead of 50 is appropriate? We are looking for proof from a reliable source.