ICD-10 Code H95.133 – Mucosal cyst of postmastoidectomy cavity, bilateral ears (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code H95.133 – Mucosal cyst of postmastoidectomy cavity, bilateral ears
What it is
This code identifies a mucosal cyst developing in the postmastoidectomy cavity in both ears. It indicates a postoperative ear cavity finding rather than a primary middle ear disease.
Clinical signs
Clinical features vary; refer to documentation. Commonly, the record may describe a visible or imaging-confirmed cystic lesion within a mastoidectomy cavity, sometimes associated with drainage, fullness, or local irritation.
When to use this code
Use H95.133 when the provider documents a mucosal cyst in the postmastoidectomy cavity affecting both ears. Code it when the condition is confirmed on exam, endoscopy, imaging, or operative findings and is not merely suspected.
Choose this code only for bilateral involvement. If the note mentions a different postoperative complication or a cyst in a non-mastoid location, check documentation before assigning H95.133.
Do not use for
Do not use this code for unilateral postmastoidectomy cavity cysts or for nonspecific ear pain alone. Do not assign it when the documentation does not clearly identify a mucosal cyst.
Coding tip
Verify laterality and postoperative site wording carefully; H95.133 requires bilateral postmastoidectomy cavity involvement.