ICD-10 Code H70.1 – Chronic mastoiditis (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code H70.1 – Chronic mastoiditis
What it is
Chronic mastoiditis is a long-standing inflammation or infection of the mastoid air cells, the bony spaces behind the ear. Use this code when the record clearly identifies the condition as chronic.
Clinical signs
Clinical features may include persistent ear pain, drainage, or a history of recurrent middle ear infection with mastoid involvement. Imaging or specialist documentation may show chronic inflammatory changes; check documentation.
When to use this code
Use H70.1 when the clinician documents chronic mastoiditis, including ongoing or recurrent mastoid inflammation. It also fits when the diagnosis appears in an ENT assessment, discharge summary, or imaging-based impression. If the note only says “mastoiditis” without chronicity, confirm the wording before coding.
Do not use for
Do not use this code for acute mastoiditis or nonspecific ear infection without mastoid involvement. If the documentation does not support a chronic process, check documentation.
Coding tip
Code the condition exactly as documented and verify whether the record specifies chronic, acute, or unspecified mastoiditis.