ICD-10-CM · Spine

M46.43

Inflammation of an intervertebral disc at the cervicothoracic junction (C7-T1 region) where the etiology has not been specified as infectious, pyogenic, or otherwise classified.

Verified May 8, 2026 · 4 sources ↓

Status: Billable
Chapter: 13
Related CPT: 9
Region: Spine

Drawn from CDCICD10DataAAPCCMS

Documentation tips

What should appear in the chart to support M46.43.

Source · Editorial brief grounded in 4 cited references ↓

Explicitly name the region as 'cervicothoracic' or reference the C7-T1 level — vague terms like 'upper back' or 'neck-back junction' will not map cleanly to M46.43 on audit.
Document the diagnostic basis: MRI findings (disc signal change on T2, end-plate edema, contrast enhancement), ESR/CRP results, and any cultures ordered — this differentiates unspecified discitis from pyogenic and supports medical necessity.
If etiology becomes clear after initial coding (e.g., culture-confirmed bacterial discitis), update the diagnosis code at the next encounter; do not continue using M46.43 once a specific cause is established.
Note the absence of a confirmed infectious source if that is the reason 'unspecified' is used — this prevents downstream payer queries about why a more specific code was not assigned.
For inpatient encounters, document all comorbidities thoroughly; MCC presence determines DRG 551 vs. 552 and directly affects reimbursement.

Related CPT procedures

Procedure codes commonly billed with M46.43. Linking the right diagnosis to the right procedure is what establishes medical necessity.

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

72141 $190.72

MRI of the cervical spinal canal and its contents performed without contrast material.

63001 $1,193.75

Posterior cervical laminectomy covering 1 or 2 vertebral segments, performed to decompress the spinal cord or cauda equina, without facetectomy, foraminotomy, or discectomy.

63015 $1,444.59

Cervical laminectomy spanning more than two vertebral segments for spinal cord or cauda equina exploration and/or decompression, performed without facetectomy, foraminotomy, or discectomy.

22554 $1,215.79

Anterior interbody arthrodesis of the cervical spine below C2, performed via anterior approach with minimal diskectomy to prepare the interspace for fusion — not performed for decompression purposes.

20610 $68.81

Aspiration and/or injection of a major joint or bursa (shoulder, hip, knee, or subacromial bursa) performed without ultrasound guidance.

72040 $39.75

Radiologic examination of the cervical spine capturing two or three views (e.g., AP, lateral, oblique).

72156 View procedure details

62323 View procedure details

72072 View procedure details

Common coding pitfalls

The recurring mistakes coders make with M46.43 and adjacent codes.

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

Confusing 'unspecified' etiology with 'unspecified site' — M46.43 is site-specific (cervicothoracic); if the site is truly unknown, use M46.40 (unspecified site), not M46.43.
Continuing to use M46.43 after a specific etiology (e.g., pyogenic, tuberculous) is confirmed — once causative organism or inflammatory subtype is documented, a more specific code in M46.2x or A18.01 should replace it.
Coding M46.43 for cervical disc degeneration or herniation — discitis is inflammatory/infectious disc involvement, not degenerative disc disease; those route to M50.x series.
Missing a secondary code for the causative organism when infection is suspected but not yet confirmed — if sepsis or bacteremia is also documented, sequence appropriately per ICD-10-CM convention.
Applying a 7th-character extension to M46.43 — M-codes in this section do not use 7th-character encounter extensions (A/D/S); that convention applies to S-code injury categories.

Clinical context

Source · Editorial summary grounded in 4 cited references ↓

M46.43 applies when the treating provider documents disc inflammation (discitis) localized to the cervicothoracic region — the transitional zone spanning the lower cervical and upper thoracic spine, typically centered at the C7-T1 level — and the underlying cause has not been specified or confirmed. The 'unspecified' qualifier means the etiology is undetermined at the time of coding: the encounter may be early in the workup, cultures may be pending, or the provider has not yet differentiated infectious from inflammatory discitis. Do not use this code once a specific etiology is established; pyogenic vertebral osteomyelitis, for example, routes to the M46.2x series.

The cervicothoracic region sits at a biomechanical inflection point between the highly mobile cervical spine and the relatively rigid, rib-supported thoracic spine. Discitis here can present with neck pain, upper back pain, referred shoulder or arm pain, and in severe cases myelopathy from cord compression. MRI with contrast is the standard imaging modality for confirming disc involvement; document signal changes, end-plate involvement, and any epidural extension in the note to support medical necessity for advanced imaging and specialist referral.

M46.43 maps to MS-DRG 551 (Medical back problems with MCC) or 552 (Medical back problems without MCC), depending on comorbidity documentation. It appears on the CMS chiropractic billing and coding article (A56273) as a covered diagnosis supporting medical necessity for chiropractic spinal manipulation, though clinical management of true discitis almost always involves infectious disease workup, spine surgery consultation, and/or interventional radiology.

Sibling codes

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

M46.42

Discitis, unspecified, cervical region

M46.47

Discitis, unspecified, lumbosacral region

M46.40

Discitis, unspecified, site unspecified

M46.41

Discitis, unspecified, occipito-atlanto-axial region

M46.49

Discitis, unspecified, multiple sites in spine

M46.48

Discitis, unspecified, sacral and sacrococcygeal region

M46.44

Discitis, unspecified, thoracic region

M46.46

Discitis, unspecified, lumbar region

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 4 cited references ↓

01What distinguishes M46.43 from M46.42 (cervical region) and M46.44 (thoracic region)?

M46.43 is reserved for disc inflammation at the cervicothoracic junction (C7-T1). If imaging and clinical documentation clearly place the discitis within the cervical region above that junction, use M46.42; if it is within the mid-to-lower thoracic spine, use M46.44. When the pathology spans or is centered at the transition zone, M46.43 is appropriate.

02When should I use M46.43 versus a code in the M46.2x pyogenic vertebral osteomyelitis series?

Use M46.43 when the etiology of disc inflammation is unspecified or pending — no confirmed organism, no documented infectious source. Once a pyogenic (bacterial) cause is confirmed, move to M46.23 (pyogenic vertebral osteomyelitis, cervicothoracic region). The 'unspecified' qualifier in M46.43 does not mean the condition is definitely non-infectious; it means etiology is not yet established.

03Does M46.43 require a secondary code for the causative organism?

Not for M46.43 specifically, because by definition the etiology is unspecified. If an organism is identified later in the encounter or if septicemia is concurrently documented, assign additional codes per ICD-10-CM sequencing guidelines. Review the tabular for any 'use additional code' instructions under the M46 category.

04Is M46.43 valid for chiropractic billing under Medicare?

Yes. CMS Local Coverage Article A56273 lists M46.43 among ICD-10-CM codes that support medical necessity for chiropractic spinal manipulation services. However, actual clinical management of discitis typically requires medical evaluation; document accordingly and ensure the treating provider's scope of practice aligns with the billed services.

05What MS-DRGs does M46.43 map to for inpatient encounters?

M46.43 groups to MS-DRG 551 (Medical back problems with MCC) or 552 (Medical back problems without MCC) under MS-DRG v43.0. Thorough comorbidity documentation is critical — an MCC-qualifying condition shifts the DRG and substantially affects reimbursement.

06Can M46.43 be used for a patient whose imaging suggests discitis but whose biopsy or culture result is still pending?

Yes. 'Unspecified' covers the scenario where the clinician has documented disc inflammation based on imaging but has not yet confirmed an etiology. Code the condition to the highest level of certainty at the time of the encounter; update if and when a specific diagnosis is established.

Sources & references

Editorial content was developed using the following public sources. Last verified May 8, 2026.

01CDC ICD-10-CM Tabular List 2026 (effective October 1, 2025)
02
icd10data.com
https://www.icd10data.com/ICD10CM/Codes/M00-M99/M45-M49/M46-/M46.43
03
aapc.com
https://www.aapc.com/codes/icd-10-codes/M46.43
04
cms.gov
https://www.cms.gov/medicare-coverage-database/view/article.aspx?articleid=56273&ver=26 (CMS Article A56273 – Billing and Coding: Chiropractic Services)

Mira AI Scribe

Mira AI Scribe captures the affected spinal region by name (cervicothoracic/C7-T1), MRI findings including disc signal abnormality and end-plate changes, laboratory inflammatory markers, and the provider's statement that etiology is undetermined or pending workup. This prevents the encounter from dropping to the unspecified-site code M46.40 and defends against payer requests for a more specific etiology code when none is yet clinically justified.

See how Mira captures M46.43 documentation