2027 ICD-10-CM Diagnosis Code S20.324ABlister (nonthermal) of middle front wall of thorax, initial encounter
S20.324A is a billable ICD-10-CM diagnosis code for blister (nonthermal) of middle front wall of thorax, initial encounter. The 7th character A marks it as an initial encounter code, used while the patient is receiving active treatment. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 606 through 607, 963 through 965. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Superficial injury; contusion, initial encounter.
Code Identity
Code Classification
Coding GuidelinesGuidance
The appropriate 7th character is to be added to each code from block Superficial injury of thorax (S20). Use the following options for the applicable episode of care:
- A - initial encounter
- D - subsequent encounter
- S - sequela
Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027, published by CMS and the National Center for Health Statistics.
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to S20.324A: its own notes plus those printed at S20, block S20-S29, and Chapter 19. A note printed at a category, block or chapter applies to every code under it.
Includes
Further defines, or gives examples of, the content of the category.
- injuries of breast
- injuries of chest (wall)
- injuries of interscapular area
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
- burns and corrosions (T20-T32)
- effects of foreign body in bronchus (T17.5)
- effects of foreign body in esophagus (T18.1)
- effects of foreign body in lung (T17.8)
- effects of foreign body in trachea (T17.4)
- frostbite (T33-T34)
- injuries of axilla
- injuries of clavicle
- injuries of scapular region
- injuries of shoulder
- insect bite or sting, venomous (T63.4)
Use Additional Code
Add a second code, after this one, to fully describe the condition.
- code to identify any retained foreign body, if applicable (Z18.-)
Notes
General instructions on how these codes are used.
- Use secondary code(s) from Chapter 20, External causes of morbidity, to indicate cause of injury. Codes within the T section that include the external cause do not require an additional external cause code
- The chapter uses the S-section for coding different types of injuries related to single body regions and the T-section to cover injuries to unspecified body regions as well as poisoning and certain other consequences of external causes.
7th Character
Every code in the category takes a 7th character from the listed values, with the placeholder X filling any empty positions before it.
- The appropriate 7th character is to be added to each code from category S20
- Ainitial encounter this code
- Dsubsequent encounter
- Ssequela
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Code History & ChangesHistory
Replacement S20.324A replaces the following previously assigned code(s):
- S20.321A - Blister (nonthermal) of right front wall of thorax, init
- S20.322A - Blister (nonthermal) of left front wall of thorax, init
- S20.329A - Blister (nonthermal) of unsp front wall of thorax, init
Questions About S20.324AOverview
What is the ICD-10 code for blister (nonthermal) of middle front wall of thorax, initial encounter?
The ICD-10-CM code for blister (nonthermal) of middle front wall of thorax, initial encounter is S20.324A (sometimes written as S20324A). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is S20.324A (Blister (nonthermal) of middle front wall of thorax) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report blister (nonthermal) of middle front wall of thorax, initial encounter on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What does the 7th character A in S20.324A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for blister (nonthermal) of middle front wall of thorax, such as an emergency visit or first evaluation.
What MS-DRG does S20.324A group to?
When blister (nonthermal) of middle front wall of thorax, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 964, 965, 607, 963, 606, with relative weights from 0.8772 to 2.6361 depending on complications. Higher weights mean higher Medicare reimbursement.
