Inflammation of one or more intervertebral discs located at the thoracolumbar junction (T12–L1 transition zone), with the etiology unspecified — meaning the record does not distinguish infectious, inflammatory, or other origin.

Documentation tips

What should appear in the chart to support M46.45.

Source · Editorial brief grounded in 5 cited references ↓

• Specify 'thoracolumbar region' or identify the T12–L1 level explicitly — 'lower thoracic' or 'upper lumbar' alone does not map to M46.45.
• Record imaging findings that support an inflammatory disc process: MRI signal change (T2 hyperintensity, Modic changes), CT evidence of endplate erosion, or nuclear medicine uptake — this separates M46.45 from a degenerative disc code on audit.
• Document whether etiology has been investigated and is still pending, or is genuinely unknown — if an organism is identified, a more specific code replaces M46.45.
• Note any prior procedural history (spinal injection, surgery) that could indicate post-procedural discitis, which may warrant an additional causative code.
• If multiple spinal levels are involved, document each level separately or use M46.49 (multiple sites) rather than forcing a single-region code.

Related CPT procedures

Procedure codes commonly billed with M46.45. Linking the right diagnosis to the right procedure is what establishes medical necessity.

Source · CMS LCDs · AAOS specialty guidance · claims-pattern analysis

Common coding pitfalls

The recurring mistakes coders make with M46.45 and adjacent codes.

Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓

• Assigning M46.45 when documentation says 'lumbar disc inflammation' — the lumbar region maps to M46.46, not M46.45; thoracolumbar is specifically the T12–L1 junction.
• Using M46.45 for degenerative disc disease without any documented inflammatory process — payers expect imaging or lab evidence of inflammation; absence may trigger a medical necessity denial.
• Confusing 'unspecified' etiology (correct use of M46.45) with 'unspecified region' — the region is fully specified here; M46.49 covers multiple or unspecified sites.
• Failing to code the causative organism separately when infection is identified — M46.45 is appropriate only while etiology remains unspecified; once a pathogen is documented, a more specific code applies.
• Selecting M46.45 for post-procedural or iatrogenic discitis without appending relevant cause codes, which can delay reimbursement and complicate clinical review.

Clinical context

Source · Editorial summary grounded in 5 cited references ↓

Sibling codes

Other billable codes under M46.4 (laterality / anatomic variants).