Chronic mastoiditis, bilateral

This code signifies a persistent inflammation of the mastoid air cells, located behind both ears. This chronic condition often results from inadequately treated acute otitis media or cholesteatoma, leading to structural changes and potential complications.

Apply this code when documentation explicitly states chronic mastoiditis affecting both the left and right mastoid processes. Supporting documentation should detail the chronicity of the inflammation, such as persistent drainage, granulation tissue, or evidence of bone erosion on imaging.

• Ensure documentation specifies "bilateral" involvement; otherwise, use a unilateral code or an unspecified laterality code if only one side is documented.
• Distinguish from acute mastoiditis (H70.0-) or recurrent acute mastoiditis, as this code is for a long-standing inflammatory process.
• Always code any associated complications, such as cholesteatoma (H71.-) or intracranial complications, in addition to this code.