Subperiosteal abscess of mastoid, left ear

This code signifies an infection that has spread from the mastoid air cells to form an abscess beneath the periosteum covering the mastoid bone, specifically in the left ear. This condition is typically a complication of acute otitis media or mastoiditis.

Apply this code when documentation clearly indicates a subperiosteal abscess of the mastoid process affecting the left ear. This diagnosis is often supported by imaging studies (e.g., CT scan) showing fluid collection beneath the mastoid periosteum and clinical signs of infection.

• Ensure laterality is explicitly documented as "left ear" to support this specific code.
• Distinguish from simple mastoiditis (H70.00-) or other types of mastoid abscesses (e.g., intracranial).
• Code any underlying acute otitis media or mastoiditis as a primary diagnosis if applicable, following sequencing guidelines.