CPT code 45399 designates an unlisted procedure on the colon and is used when no specific CPT code accurately describes the performed colon procedure. Nationally, unlisted procedure codes like 45399 matter because they require supplemental documentation for claims adjudication and can affect payment consistency, utilization tracking, and clinical reporting. Payers commonly involved in processing claims for this code include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare.

This publication provides a concise national overview of CPT code 45399: what the code represents, the typical clinical and site-of-service contexts where it is used, and the administrative considerations that commonly accompany unlisted procedure reporting. Readers will find guidance on the documentation expectations associated with unlisted colon procedures, an outline of common payer engagement for claim review, and discussion of where 45399 fits in clinical coding workflows. The report highlights benchmarking and policy-related themes relevant to payers and providers, and it identifies where additional clinical detail is typically required to support medical necessity and payment decisions. Data not available in the input is noted where applicable.