ICD-10 Code J21.9 – Acute bronchiolitis, unspecified (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code J21.9 – Acute bronchiolitis, unspecified
What it is
J21.9 identifies acute bronchiolitis when the specific cause is not documented. It refers to inflammation of the small airways in the lungs, usually in an acute respiratory illness.
Clinical signs
Common findings include cough, wheezing, tachypnea, and increased work of breathing. Clinical features vary; refer to documentation for the provider’s diagnosis and any noted lower-airway involvement.
When to use this code
Use J21.9 when the record states acute bronchiolitis but does not name an organism or other specific type. It also fits when the clinician documents bronchiolitis without further detail. If a more specific cause is documented, code that instead.
Do not use for
Do not use this code for bronchitis, pneumonia, or wheezing alone without a bronchiolitis diagnosis. Check documentation if the chart identifies a specific viral or other cause.
Coding tip
Assign J21.9 only when the diagnosis is explicitly documented and no more specific bronchiolitis code is supported.