S90.422A (Blister (nonthermal), left great toe, initial encounter) compared with S90.422D (Blister (nonthermal), left great toe, subsequent encounter), from the official CMS tabular data. S90.422A and S90.422D code the same injury at a different phase of treatment.
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
Same injury, other encounter phase. S90.422A and S90.422D 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.
| S90.422ABlister (nonthermal), left great toe, initial encounter | S90.422DBlister (nonthermal), left great toe, subsequent encounter | |
|---|---|---|
| Billing status | Billable | Billable |
| 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), left great toe, initial encounter is a billable ICD-10-CM diagnosis code (S90.422A). | Blister (nonthermal), left great toe, subsequent encounter is a billable ICD-10-CM diagnosis code (S90.422D). |
| 7th character | The appropriate 7th character is to be added to each code from category S90 | The appropriate 7th character is to be added to each code from category S90 |
Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources