ICD-10 Code H70.12 – Chronic mastoiditis, left ear (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code H70.12 – Chronic mastoiditis, left ear
What it is
H70.12 identifies chronic inflammation or infection of the mastoid air cells in the left ear. Use it when the condition is documented as chronic and limited to the left side.
Clinical signs
Typical findings may include persistent ear pain, drainage, hearing changes, or tenderness behind the ear. Clinical features vary; refer to documentation.
When to use this code
Use this code when the provider documents chronic mastoiditis affecting the left mastoid or left ear. It also fits follow-up visits when the diagnosis remains active and is still being managed or evaluated.
If the record only says mastoiditis without laterality or chronicity, check documentation before assigning H70.12. Code the documented side and acuity exactly as written.
Do not use for
Do not use H70.12 for acute mastoiditis or for unspecified mastoiditis. If the left side is not documented, check documentation.
Coding tip
Match both chronicity and laterality in the note before assigning H70.12.