2026 ICD-10-CM Diagnosis Code H70.10Chronic mastoiditis, unspecified ear

ICD-10-CM Codes›H60–H95›H65-H75›H70

ICD-10-CM H70.10
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

H70.10 is a billable ICD-10-CM diagnosis code for chronic mastoiditis, unspecified ear. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 152 through 153. Coders also document this condition as caries of mastoid. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Diseases of middle ear and mastoid (except otitis media).

Code Identity

ICD-10-CM Code
H70.10
Billable Status
Yes — Valid for Submission
Code Describes
Chronic mastoiditis, unspecified ear
Short Description
Chronic mastoiditis, unspecified ear
Same as the full description in the CMS dataset.
Parent Code
H70.1
Chronic mastoiditis

Code Classification

ChapterH60–H95Diseases of the ear and mastoid process
SectionH65-H75Diseases of middle ear and mastoid
CategoryH70Mastoiditis and related conditions
This CodeH70.10Chronic mastoiditis, unspecified ear

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Caries of mastoid
  • Chronic inflammation of mastoid cavity
  • Chronic mastoiditis
  • Chronic suppurative mastoiditis
  • Fistula of mastoid
  • Injury of mastoid

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR EAR002
Diseases of middle ear and mastoid (except otitis media)
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Ear Infections

Ear infections are the most common reason parents bring their child to a doctor. Three out of four children will have at least one ear infection by their third birthday. Adults can also get ear infections, but they are less common.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert H70.10 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
383.1 Chronic mastoiditis
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About H70.10Overview

Is H70.10 (Chronic mastoiditis) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report chronic mastoiditis, unspecified ear on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does H70.10 group to?

When chronic mastoiditis, unspecified ear is the principal diagnosis on an inpatient stay, it groups to MS-DRG 152, 153, with relative weights from 0.7382 to 1.1822 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of H70.10?

Under the General Equivalence Mappings, chronic mastoiditis, unspecified ear converts to ICD-9-CM 383.1 (chronic mastoiditis). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.