ICD-10 Code H70.01 – Subperiosteal Abscess of Mastoid (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code H70.01 – Subperiosteal abscess of mastoid
What it is
H70.01 identifies a subperiosteal abscess involving the mastoid region. It means pus has collected beneath the periosteum over the mastoid bone, usually as a complication of mastoiditis.
Clinical signs
Typical findings include postauricular swelling, tenderness, and redness, often with the ear pushed forward. Clinical features vary; refer to documentation for the exact presentation and associated ear findings.
When to use this code
Use this code when the provider documents a subperiosteal abscess of the mastoid, including cases described as mastoid abscess with subperiosteal extension. It is appropriate when the diagnosis is clearly stated in the record. Check documentation if the note only mentions mastoiditis without abscess.
Do not use for
Do not use H70.01 for uncomplicated mastoiditis, nonspecific ear pain, or other ear infections without a documented subperiosteal abscess. If the record is unclear, check documentation.
Coding tip
Code H70.01 only when the abscess is specifically linked to the mastoid in the provider’s documentation.