CPT code 78599 is the unlisted CPT code for respiratory diagnostic nuclear medicine procedures and is used when no specific respiratory nuclear medicine CPT code applies. Nationally, unlisted codes like 78599 are important because they provide a billing pathway for uncommon, bespoke, or emerging pulmonary imaging studies that rely on radiopharmaceuticals to evaluate lung function or pathology. Proper use of 78599 ensures these services can be reported when clinical circumstances fall outside established code definitions.

Key payers in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of clinical context for respiratory nuclear medicine, payer coverage considerations, and typical sites of service. The publication outlines how 78599 differs from specific CPT codes, the role of unlisted codes in supporting novel or atypical procedures, and practical documentation expectations that payers commonly require for adjudication.

This report does not provide state-specific guidance. It aims to inform clinicians, coding professionals, and revenue cycle staff about where 78599 fits in the coding landscape, what to expect from major national payers, and which clinical scenarios commonly lead to use of an unlisted respiratory nuclear medicine code.