T79.A0XA
Compartment syndrome, unspecified, initial encounter
T79.A0XA (also written T79A0XA) is a billable ICD-10-CM diagnosis code for compartment syndrome, unspecified, initial encounter. It is part of the FY2027 code set, effective October 1, 2026. It is one of the 54 codes in category T79 (Certain early complications of trauma, not elsewhere classified). The Alphabetic Index lists it under 2 entries. Its 7th character, A, means initial encounter. Its coding notes include a Use additional code instruction, 2 Excludes1 entries and 7 Excludes2 entries.
7th character
Category T79 requires a 7th character. T79.A0 has only 5 characters, so a placeholder X fills the 6th position.
Guidelines tip
From the FY2027 Official Guidelines. ICD10Ref adds no rules of its own.
The 7th character depends on whether the patient is in active treatment, not on who sees the patient. An aftercare Z code is not used for injury aftercare.
Use additional code
Add the listed code as a secondary code, if known.
Also from chapter/block level (1 note)
- code to identify any retained foreign body, if applicable (Z18.-)
Excludes1
Not coded here. The listed conditions generally should not be reported together.
Excludes2
Not included here. Both codes may be reported if the patient has both conditions.
Also from chapter/block level (2 notes)
- birth trauma (P10-P15)
- obstetric trauma (O70-O71)
Care settings
How CMS programs treat this code. These are CMS claim edits and list entries, not coverage or eligibility rules.
Hospital CC
Counts as a complication or comorbidity (CC) when reported as a secondary diagnosis on an inpatient claim. It does not count when the principal diagnosis is one of the 72 codes in its exclusion list. Some MS-DRGs also ignore a CC or MCC that defines the DRG.
Source: CMS MS-DRG Definitions Manual v44, effective October 1, 2026, Appendix CInclusion terms
Conditions classified to this code.
- Compartment syndrome NOS
Notes
Also from chapter/block level (2 notes)
- Use secondary code(s) from Chapter 20, External causes of morbidity, to indicate cause of injury. Codes within the T section that include the external cause do not require an additional external cause code
- The chapter uses the S-section for coding different types of injuries related to single body regions and the T-section to cover injuries to unspecified body regions as well as poisoning and certain other consequences of external causes.
Alphabetic Index terms
Terms the official Alphabetic Index lists for T79.A0. This code adds the 7th character. 2 entries