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S21.402A vs S21.402S

S21.402A (Unspecified open wound of left back wall of thorax with penetration into thoracic cavity, initial encounter) compared with S21.402S (Unspecified open wound of left back wall of thorax with penetration into thoracic cavity, sequela), from the official CMS tabular data. S21.402A and S21.402S code the same injury at a different phase of treatment.

Relationship

Review

Encounter relationship

S21.402A
Initial encounter
Unspecified open wound of left back wall of thorax with penetration into thoracic cavity, initial encounter
↔
S21.402S
Sequela
Unspecified open wound of left back wall of thorax with penetration into thoracic cavity, sequela

Same underlying diagnosis, different encounter phase.

The 7th character records the phase of care for the encounter being coded, so a single encounter takes one of these characters, not several. Review whether both phases belong on the same episode of care.

Source: ICD-10-CM Official Guidelines, Section I.C.19.a

Can these codes be reported together?

Same injury, other encounter phase. S21.402A and S21.402S code the same injury at a different phase of treatment, set by the 7th character.

The 7th character records the type of care given at the encounter being coded (ICD-10-CM Official Guidelines, Section I.C.19.a), so one encounter takes one of these, not both.

Side by side

S21.402AUnspecified open wound of left back wall of thorax with penetration into thoracic cavity, initial encounterS21.402SUnspecified open wound of left back wall of thorax with penetration into thoracic cavity, sequela
Billing statusBillableBillable
ClassificationS00-T88 — Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88)S00-T88 — Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88)
DefinitionUnspecified open wound of left back wall of thorax with penetration into thoracic cavity, initial encounter is a billable ICD-10-CM diagnosis code (S21.402A).Unspecified open wound of left back wall of thorax with penetration into thoracic cavity, sequela is a billable ICD-10-CM diagnosis code (S21.402S).
7th characterThe appropriate 7th character is to be added to each code from category S21The appropriate 7th character is to be added to each code from category S21
Includes
injuries of breast
injuries of chest (wall)
injuries of interscapular area
injuries of breast
injuries of chest (wall)
injuries of interscapular area
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Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources