H70.001 ICD-10-CM Code: Acute mastoiditis without complications, right ear

Coder workflow for H70.001

MedCoder structured workflow — derived from this code’s own official record

Before you code H70.001

1. Laterality is coded in this family. Confirm the side documented — right, left, or bilateral — and select the matching code (this page’s code: right). The unspecified-side code applies only when the record states no side. Laterality is assigned from the documented side; where a bilateral code exists and both sides are documented, it is used instead of two unilateral codes (Guidelines I.B.13).

   ReviewH70.002 · left, H70.003 · bilateral, H70.009 · unspecified

   Guide: Laterality coding →

Choose the right path

1. Is the side documented?
   Yes → Select the code for the documented side (or the bilateral code when both sides are documented and one exists).
   No → Use the unspecified-side code only when the record states no side; a query is the alternative.

   ReviewH70.002 · left, H70.003 · bilateral, H70.009 · unspecified

Consider H70.001. Then confirm the code is valid for the date of service in the Verify section.

Documentation check

The provider’s diagnostic statement

Codes are assigned from the provider’s documented diagnosis, not from clinical criteria, test values or a medication list (Guidelines I.A.19).

Laterality

Right, left or bilateral as documented; unspecified only when the record states no side (Guidelines I.B.13).

Acuity

Acute or chronic as documented; when both are documented and separate codes exist, both are reported with the acute code first (Guidelines I.B.8).

The associated condition or complication

Whether the associated condition the title names is documented; the “with” convention presumes some links, and a provider statement that the conditions are unrelated defeats it (Guidelines I.A.15).

Coding decision scenarios

Pattern scenarios for this code’s structure — decision rules, not clinical cases

Every row is derived from this code’s own record — its title, tabular notes, 7th-character family and same-category siblings — with fixed MedCoder wording; nothing is inferred about a patient. The official notes and guideline text are in the sections each row links to, and they control.

Official Coding Guidelines

No excerpt in the ICD-10-CM Official Guidelines names this code specifically. Its chapter carries only this chapter-wide note:

Don’t confuse H70.001 with…

MedCoder analysis — pairs from this code’s official notes, distinctions written by MedCoder

The codes most likely to be picked instead of H70.001 — named in its own official notes, or sharing its laterality or encounter family — with what separates them and which documentation moves the case. Each links to the full comparison.

• H70.009— Specificity relationship (Review)

  Overlapping diagnoses in the same category.

  Overlapping codes in the same category — the documentation decides which is the more specific fit.

  What moves you there: A record that documents no more than “Acute mastoiditis without complications, unspecified ear” takes H70.009; specificity in the record moves it back here.

  Full comparison: H70.001 vs H70.009 →

• H70.002— Laterality relationship (Review)

  Same condition; these differ only in which side is documented.

  The same condition on the other side; the documented side decides, and a bilateral code, where one exists, replaces the pair when both sides are documented.

  What moves you there: A documented left side moves the case to H70.002.

  Full comparison: H70.001 vs H70.002 →

• H70.003— Laterality relationship (Review)

  Same condition; these differ only in which side is documented.

  The same condition on the other side; the documented side decides, and a bilateral code, where one exists, replaces the pair when both sides are documented.

  What moves you there: Documentation of both sides moves the case to H70.003.

  Full comparison: H70.001 vs H70.003 →

Relationships are read from this code's own official notes, its laterality siblings and its encounter family; the wording of each distinction is MedCoder editorial, and the documentation named in each “what moves you there” line is the official note phrase or sibling title itself. Source: CMS ICD-10-CM tabular instructional notes; ICD-10-CM Official Guidelines, Section I.A.12.a.

Verify Before Coding

• CC as a secondary diagnosis (FY2026). Can raise the stay's MS-DRG severity tier.

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder structured relationships — computed from published CMS and AHRQ datasets

Other codes that name H70.001 or its code family, from the CMS ICD-10-CM tabular instructional notes. Tabular-note edges are stored at the code family level that carries each note.

Referenced by 1 Excludes2 note: H74 — Other disorders of middle ear mastoid (via H70.-).

These codes’ tabular lists name this diagnosis as distinct — both may be reported when both are documented.

MS-DRG Grouper Relationships (FY2026)

Potential MS-DRG participation — not a DRG assignment.

FY2026 MS-DRG: CC — Complication or Comorbidity. Reported as a secondary diagnosis, this code raises the stay's MS-DRG severity tier — except when the principal diagnosis is one of 76 clinically related codes on its CMS exclusion list.

Named in the grouper logic of 2 MS-DRGs: DRG 152 (MDC 03), DRG 153 (MDC 03).

From the CMS MS-DRG Definitions Manual (Appendices B and C). Actual DRG assignment depends on the complete claim.

Clinical classification (AHRQ CCSR):EAR002 — Diseases of middle ear and mastoid (except otitis media) (default).

Clinical Classifications Software Refined (CCSR) for ICD-10-CM Diagnoses. Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality.

Related Codes

Same clinical process (MS-DRG)

Acts as CC — raises the severity of other admissions. CMS groups these diagnoses into one MS-DRG principal-diagnosis exclusion process — a CC/MCC on this list never raises severity when the principal diagnosis is also on it.

A17.9 — Tuberculosis of nervous system, unspecified, A18.6 — Tuberculosis of (inner) (middle) ear, A18.82 — Tuberculosis of other endocrine glands, A18.84 — Tuberculosis of heart, A18.89 — Tuberculosis of other sites, H70.002 — Acute mastoiditis without complications, left ear, H70.003 — Acute mastoiditis without complications, bilateral, H70.009 — Acute mastoiditis without complications, unspecified ear, H70.011 — Subperiosteal abscess of mastoid, right ear, H70.012 — Subperiosteal abscess of mastoid, left ear, H70.013 — Subperiosteal abscess of mastoid, bilateral, H70.019 — Subperiosteal abscess of mastoid, unspecified ear, H70.091 — Acute mastoiditis with other complications, right ear, H70.092 — Acute mastoiditis with other complications, left ear, H70.093 — Acute mastoiditis with other complications, bilateral, H70.099 — Acute mastoiditis with other complications, unspecified ear, H70.10 — Chronic mastoiditis, unspecified ear, H70.11 — Chronic mastoiditis, right ear, H70.12 — Chronic mastoiditis, left ear, H70.13 — Chronic mastoiditis, bilateral, +55 more

Same condition, opposite side

Same category and title, differing only in which side of the body is affected.

H70.002 — Acute mastoiditis without complications, left ear (left)Compare H70.001 vs H70.002 →, H70.003 — Acute mastoiditis without complications, bilateral (bilateral)Compare H70.001 vs H70.003 →, H70.009 — Acute mastoiditis without complications, unspecified ear (unspecified)Compare H70.001 vs H70.009 →

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical category (Diseases of middle ear and mastoid (except otitis media)).

H69.02 — Patulous Eustachian tube, left ear, H69.03 — Patulous Eustachian tube, bilateral, H69.80 — Other specified disorders of Eustachian tube, unspecified ear, H69.81 — Other specified disorders of Eustachian tube, right ear, H69.82 — Other specified disorders of Eustachian tube, left ear, H69.83 — Other specified disorders of Eustachian tube, bilateral, H69.90 — Unspecified Eustachian tube disorder, unspecified ear, H69.91 — Unspecified Eustachian tube disorder, right ear, H69.92 — Unspecified Eustachian tube disorder, left ear, H69.93 — Unspecified Eustachian tube disorder, bilateral, H70.002 — Acute mastoiditis without complications, left ear, H70.003 — Acute mastoiditis without complications, bilateral, H70.009 — Acute mastoiditis without complications, unspecified ear, H70.011 — Subperiosteal abscess of mastoid, right ear, H70.012 — Subperiosteal abscess of mastoid, left ear, H70.013 — Subperiosteal abscess of mastoid, bilateral, H70.019 — Subperiosteal abscess of mastoid, unspecified ear, H70.091 — Acute mastoiditis with other complications, right ear, H70.092 — Acute mastoiditis with other complications, left ear, H70.093 — Acute mastoiditis with other complications, bilateral, +204 more

Same Index main term, other category

The ICD-10-CM Index to Diseases and Injuries files this code under the main term “Mastoiditis”; these codes share that main term but sit in a different category of the Tabular List.

A18.03 — Tuberculosis of other bones (tuberculous), B89 — Unspecified parasitic disease (in, parasitic disease NEC), B99 — Other and unspecified infectious diseases (in, infectious disease NEC)

Contextual Map

Every relationship of H70.001 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Run H70.001 with this related code in Claim Check

Hierarchy

• H60-H95 — Chapter 8: Diseases of the Ear and Mastoid Process (H60-H95) (H60-H95)[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• H65-H75 — Diseases of middle ear and mastoid[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026

Referenced by Excludes2 notes

• H74 — Other disorders of middle ear mastoid[Excludes2](via H70.-): “mastoiditis (H70.-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Clinical classification (CCSR)

• EAR002 — Diseases of middle ear and mastoid (except otitis media)[CCSR]— AHRQ CCSR for ICD-10-CM Diagnoses (HCUP)

MS-DRG Grouper

• CC — Complication or Comorbidity [MS-DRG severity]: “As a secondary diagnosis this code can raise the stay's MS-DRG severity tier (CC).”— CMS MS-DRG Definitions Manual (Appendix C) · FY2026
• DRG 152 — OTITIS MEDIA AND URI WITH MCC[MS-DRG]: “OTITIS MEDIA AND URI WITH MCC (MDC 03)”— CMS MS-DRG Definitions Manual (Appendix B) · FY2026
• DRG 153 — OTITIS MEDIA AND URI WITHOUT MCC[MS-DRG]: “OTITIS MEDIA AND URI WITHOUT MCC (MDC 03)”— CMS MS-DRG Definitions Manual (Appendix B) · FY2026

MDC crossing

• MDC 03 — Diseases and Disorders of the Ear, Nose, Mouth and Throat[MDC crossing]: “Diseases and Disorders of the Ear, Nose, Mouth and Throat — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs. 5,147 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2026

Nearest codes (40)

• H70 — Mastoiditis and related conditions[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• H70.0 — Acute mastoiditis[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• H70.00 — Acute mastoiditis without complications[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• H70.002 — Acute mastoiditis without complications, left ear[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• H70.003 — Acute mastoiditis without complications, bilateral[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• H70.009 — Acute mastoiditis without complications, unspecified ear[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• H70.01 — Subperiosteal abscess of mastoid[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• H70.011 — Subperiosteal abscess of mastoid, right ear[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• and 32 more

Change history

• FY2016 — In the code set at ICD-10-CM adoption [Change history]— CMS release files (code change ledger) · icd10cm-fy2016

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data

CMS/CDC ICD-10-CM FY2026 tabular list, index and tables, effective October 1, 2025 Release, file and checksum · Publisher’s page

Coding guidelines Official source data

ICD-10-CM Official Guidelines for Coding and Reporting (FY2026), quoted by section Release, file and checksum · Publisher’s page

Claim edits Official source data

CMS Definitions of Medicare Code Edits — v43.1 (April 2026) Release, file and checksum · Publisher’s page

Inpatient payment groups Official source data

CMS MS-DRG Definitions Manual (incl. Appendix B diagnosis index, Appendix C CC/MCC list, Appendix E procedure index) and IPPS Final Rule tables — v43 Release, file and checksum · Publisher’s page

Change history and date-of-service validity Official source data

CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page

Comparisons, relationships and the contextual map MedCoder structured relationship

Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears

Summary and FAQ answers MedCoder explanation

Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Labels on this page: Official source data · MedCoder structured relationship · MedCoder explanation. How to read the labels · All data sources and release dates

Nearest Codes in This Family

Official ICD-10-CM classifications closest to H70.001 in its code family, with their registry titles.

• H70 — Mastoiditis and related conditions
• H70.0 — Acute mastoiditis
• H70.00 — Acute mastoiditis without complications
• H70.002 — Acute mastoiditis without complications, left ear
• H70.003 — Acute mastoiditis without complications, bilateral
• H70.009 — Acute mastoiditis without complications, unspecified ear
• H70.01 — Subperiosteal abscess of mastoid
• H70.011 — Subperiosteal abscess of mastoid, right ear
• H70.012 — Subperiosteal abscess of mastoid, left ear
• H70.013 — Subperiosteal abscess of mastoid, bilateral

View all codes in the H70 family