M79.A21 — Nontraumatic compartment syndrome of right lower extremity
Is M79.A21 billable?
Yes — M79.A21 is billable for FY2027. M79.A21 is a valid, billable ICD-10-CM code at the highest level of specificity in its branch. M79.A21 may be submitted for encounters from October 1, 2026 through September 30, 2027.
M79.A21 at a glance
| Code | M79.A21 |
|---|---|
| Description | Nontraumatic compartment syndrome of right lower extremity |
| Billable | Yes |
| Code set | ICD-10-CM FY2027 |
| Valid for encounters | October 1, 2026 – September 30, 2027 |
Which MS-DRGs does M79.A21 group to?
M79.A21 sits in MDC 08 and helps define the logic of 2 MS-DRGs (version 44, FY2027). Which one a stay actually groups to also depends on procedures and secondary diagnoses.
- 557Tendonitis, Myositis and Bursitis with MCCmedical
- 558Tendonitis, Myositis and Bursitis without MCCmedical
As a secondary diagnosis, M79.A21 is a complication or comorbidity (CC), which can move a stay into a higher-paying DRG.
How is M79.A21 listed in the Alphabetic Index?
The Alphabetic Index lists these routes under M79.A2, the nearest indexed parent of M79.A21. Use them to find the family, then select the specific code.
- Compartment syndrome › nontraumatic › lower extremity (deep) (posterior) (traumatic)
- Syndrome › compartment › nontraumatic › lower extremity
Excludes1 — never code together — inherited from M79
The conditions below can never be reported together with M79.A21 on the same claim. An Excludes1 note means the two conditions cannot occur in the same patient, so reporting both is a coding error.
Excludes1 — never code together — inherited from M79.A
The conditions below can never be reported together with M79.A21 on the same claim. An Excludes1 note means the two conditions cannot occur in the same patient, so reporting both is a coding error.
Code first — inherited from M79.A
The underlying condition below must be sequenced before M79.A21. M79.A21 describes a manifestation and cannot be the principal or first-listed diagnosis.
- , if applicable, associated postprocedural complication
Excludes2 — not included here — inherited from Chapter 13
The conditions below are not part of M79.A21, but a patient may have both at the same time. When documentation supports it, M79.A21 and the excluded code may both be reported.
- arthropathic psoriasis (L40.5-)
- certain conditions originating in the perinatal period (P04-P96)
- certain infectious and parasitic diseases (A00-B99)
- compartment syndrome (traumatic) (T79.A-)
- complications of pregnancy, childbirth and the puerperium (O00-O9A)
- congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
- endocrine, nutritional and metabolic diseases (E00-E88)
- injury, poisoning and certain other consequences of external causes (S00-T88)
- neoplasms (C00-D49)
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
How long has M79.A21 existed?
M79.A21 has been in ICD-10-CM since at least FY2016, the earliest fiscal year on record here.
Derived from the official order files for FY2016–FY2026. FY2017 and FY2020 publish no order file, so those years are not covered.