Mucosal cyst of postmastoidectomy cavity, left ear

This code describes a fluid-filled sac lined with mucous membrane that develops within the space created after a mastoidectomy procedure in the left ear. These cysts are typically benign and can cause symptoms such as ear fullness, drainage, or hearing loss. They represent a late complication of mastoid surgery.

Use this code when documentation clearly indicates a mucosal cyst has formed within the post-surgical cavity of the left mastoid bone. This diagnosis is typically made through otoscopic examination, imaging studies (e.g., CT scan), or surgical exploration. The patient must have a history of a mastoidectomy on the left side.

• Ensure documentation specifies "mucosal cyst" and not another type of cyst or granuloma.
• Verify the laterality is explicitly stated as "left ear" to avoid incorrect coding.
• Do not use this code for cysts in an intact mastoid or for other post-mastoidectomy complications like cholesteatoma.