ICD-10 Code H95.13 – Mucosal cyst of postmastoidectomy cavity (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code H95.13 – Mucosal cyst of postmastoidectomy cavity
What it is
H95.13 identifies a mucosal cyst that develops in a postmastoidectomy cavity. Use it for a cystic lesion arising in the surgically altered mastoid space, not for general ear disease.
Clinical signs
Findings may include a visible or imaging-confirmed cystic mass within the mastoid cavity. Clinical features vary; refer to documentation for symptoms such as drainage, fullness, or recurrent local irritation.
When to use this code
Use this code when the record clearly documents a mucosal cyst in a cavity created after mastoidectomy. It fits postoperative ear follow-up when the cyst is the diagnosed condition. If the note only mentions a mastoid cavity abnormality without a cyst, check documentation.
Do not use for
Do not use H95.13 for uncomplicated postmastoidectomy status or for nonspecific postoperative ear pain. It is also not appropriate for other middle ear or mastoid lesions unless a mucosal cyst is documented.
Coding tip
Confirm both the prior mastoidectomy and the cyst diagnosis in the provider note before assigning H95.13.