2026 ICD-10-CM Diagnosis Code S27.421AContusion of bronchus, unilateral, initial encounter
S27.421A is a billable ICD-10-CM diagnosis code for contusion of bronchus, unilateral, 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 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 183 through 185, 963 through 965. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Internal organ injury, initial encounter.
Code Identity
Code Classification
Coding GuidelinesGuidance
The appropriate 7th character is to be added to each code from block Injury of other and unspecified intrathoracic organs (S27). 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 2026, published by CMS and the National Center for Health Statistics.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Patient EducationClinical
Chest Injuries and Disorders
The chest is the part of your body between your neck and your abdomen (belly). The medical term for your chest is thorax.
The full article covers:
- What is the chest?
- What are chest injuries and disorders?
- How are chest injuries and disorders diagnosed?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert S27.421A to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About S27.421AOverview
Is S27.421A (Contusion of bronchus, unilateral) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report contusion of bronchus, unilateral, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in S27.421A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for contusion of bronchus, unilateral, such as an emergency visit or first evaluation.
What MS-DRG does S27.421A group to?
When contusion of bronchus, unilateral, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 183, 184, 185, 963, 964, 965, with relative weights from 0.7865 to 2.7338 depending on complications. Higher weights mean higher Medicare reimbursement.
What is the ICD-9 equivalent of S27.421A?
Under the General Equivalence Mappings, contusion of bronchus, unilateral, initial encounter converts to ICD-9-CM 862.21 (bronchus injury-closed). The mapping is approximate, so confirm the match fits the documentation.
Footnotes
[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.
