| S20.421 | Blister (nonthermal) of right back wall of thorax | NON-BILLABLE CODE |
| S20.421A | Blister (nonthermal) of right back wall of thorax, initial encounter | BILLABLE CODE |
| S20.421D | Blister (nonthermal) of right back wall of thorax, subsequent encounter | BILLABLE CODE |
| S20.421S | Blister (nonthermal) of right back wall of thorax, sequela | BILLABLE CODE |
| S20.422 | Blister (nonthermal) of left back wall of thorax | NON-BILLABLE CODE |
| S20.422A | Blister (nonthermal) of left back wall of thorax, initial encounter | BILLABLE CODE |
| S20.422D | Blister (nonthermal) of left back wall of thorax, subsequent encounter | BILLABLE CODE |
| S20.422S | Blister (nonthermal) of left back wall of thorax, sequela | BILLABLE CODE |
| S20.429 | Blister (nonthermal) of unspecified back wall of thorax | NON-BILLABLE CODE |
| S20.429A | Blister (nonthermal) of unspecified back wall of thorax, initial encounter | BILLABLE CODE |
| S20.429D | Blister (nonthermal) of unspecified back wall of thorax, subsequent encounter | BILLABLE CODE |
| S20.429S | Blister (nonthermal) of unspecified back wall of thorax, sequela | BILLABLE CODE |
