ICD-10-CM > S00-T88 > S20-S29 > S20 > S20.4 > S20.42 > S20.422 S20.422 Blister (nonthermal) of left back wall of thorax Non-Billable/Non-Specific Codes S20.422A..., initial encounterS20.422D..., subsequent encounterS20.422S..., sequela