S20.421 (Blister (nonthermal) of right back wall of thorax) compared with S20.422 (Blister (nonthermal) of left back wall of thorax), from the official CMS tabular data. S20.421 and S20.422 code the same condition on opposite sides.
Same condition; these differ only in which side is documented.
These codes share a category and title and differ only in the side affected. The documentation decides which applies, and a bilateral code is reported only where the code set provides one.
Source: ICD-10-CM tabular list (laterality variant derived from the code title)
Same condition, opposite side. S20.421 and S20.422 name the same condition on opposite sides of the body.
Same category and title, differing only in which side is affected — the documentation decides which one applies, and a bilateral code is reported only where the code set provides one.
| S20.421Blister (nonthermal) of right back wall of thorax | S20.422Blister (nonthermal) of left back wall of thorax | |
|---|---|---|
| Billing status | Non-billable header | Non-billable header |
| Classification | S00-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) |
| Definition | Blister (nonthermal) of right back wall of thorax is a non-billable ICD-10-CM category code (S20.421). | Blister (nonthermal) of left back wall of thorax is a non-billable ICD-10-CM category code (S20.422). |
| 7th character | The appropriate 7th character is to be added to each code from category S20 | The appropriate 7th character is to be added to each code from category S20 |
| Includes | injuries of breast injuries of chest (wall) injuries of interscapular area | injuries of breast injuries of chest (wall) injuries of interscapular area |
Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources