S90.561A (Insect bite (nonvenomous), right ankle, initial encounter) compared with S90.561S (Insect bite (nonvenomous), right ankle, sequela), from the official CMS tabular data. S90.561A and S90.561S 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. S90.561A and S90.561S 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.
| S90.561AInsect bite (nonvenomous), right ankle, initial encounter | S90.561SInsect bite (nonvenomous), right ankle, sequela | |
|---|---|---|
| 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 | Insect bite (nonvenomous), right ankle, initial encounter is a billable ICD-10-CM diagnosis code (S90.561A). | Insect bite (nonvenomous), right ankle, sequela is a billable ICD-10-CM diagnosis code (S90.561S). |
| 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