ICD-10-CM diagnosis code
S21.209A Unspecified open wound of unspecified back wall of thorax without penetration into thoracic cavity, initial encounter
- Billable
- Yes, a complete code (FY2026)
- Category
- S21 Open wound of thorax
Encounter (7th character)
This code is for the initial encounter: the patient is receiving active treatment for the condition (for example surgery, an emergency department visit or evaluation by a new clinician).
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Other codes in S21
288 complete codes in this category.
- S21.201AUnspecified open wound of right back wall of thorax without penetration into thoracic cavity, initial encounter
- S21.201DUnspecified open wound of right back wall of thorax without penetration into thoracic cavity, subsequent encounter
- S21.201SUnspecified open wound of right back wall of thorax without penetration into thoracic cavity, sequela
- S21.202AUnspecified open wound of left back wall of thorax without penetration into thoracic cavity, initial encounter
- S21.202DUnspecified open wound of left back wall of thorax without penetration into thoracic cavity, subsequent encounter
- S21.202SUnspecified open wound of left back wall of thorax without penetration into thoracic cavity, sequela
- S21.209AUnspecified open wound of unspecified back wall of thorax without penetration into thoracic cavity, initial encounter
- S21.209DUnspecified open wound of unspecified back wall of thorax without penetration into thoracic cavity, subsequent encounter
- S21.209SUnspecified open wound of unspecified back wall of thorax without penetration into thoracic cavity, sequela
- S21.211ALaceration without foreign body of right back wall of thorax without penetration into thoracic cavity, initial encounter
- S21.211DLaceration without foreign body of right back wall of thorax without penetration into thoracic cavity, subsequent encounter
- S21.211SLaceration without foreign body of right back wall of thorax without penetration into thoracic cavity, sequela
Documentation tips
- Make sure the note supports every element of the title, “Unspecified open wound of unspecified back wall of thorax without penetration into thoracic cavity, initial encounter”: each detail in it should be traceable to the history, examination or assessment.
- Code to the highest specificity the documentation supports. If a detail is missing from the note, add it to the note rather than choosing a less specific code by default.
- Check the Tabular List and official guidelines for instructional notes (“code first”, “use additional code”, Excludes1/Excludes2) that apply to S21.
The international WHO ICD-10 also has S21, with its inclusion and exclusion notes; titles and detail can differ from ICD-10-CM.
ICD-10-CM is developed by the National Center for Health Statistics (NCHS), Centers for Disease Control and Prevention, U.S. Department of Health and Human Services, and is based on the WHO ICD-10. Codes and titles are reproduced unchanged from the FY2026 code list (effective 1 October 2025). Their use here does not imply endorsement by CDC, HHS or the U.S. Government. Changes effective on or after 1 October 2026 may not be reflected yet; check the current release at cdc.gov or cms.gov before submitting claims.
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