ICD-10 Code for Mastoiditis

The default ICD-10-CM 2027 code for mastoiditis (coalescent) (hemorrhagic) (suppurative) is H70.9 – Unspecified mastoiditis (a header – choose a more specific code). More specific codes depend on the details documented, as listed in the official index (10 codes, 2 billable).

Main code: H70.9 – Unspecified mastoiditis
Billable: No – header code

Index entries for Mastoiditis

acute, subacute – H70.00- (header)
- complicated NEC – H70.09- (header)
- subperiosteal – H70.01- (header)
chronic (necrotic) (recurrent) – H70.1- (header)
in (due to)
- infectious disease NEC – B99 (header) – H75.0- (header) [manifestation]
- parasitic disease NEC – B89 – H75.0- (header) [manifestation]
- tuberculosis – A18.03
petrositis – see Petrositis
postauricular fistula – see Fistula, postauricular
specified NEC – H70.89- (header)
tuberculous – A18.03

How to choose the right code

Start with the main term, then pick the indented subterm that matches the documentation (type, cause, site, laterality, episode of care). Always confirm the code in the tabular list: follow its Excludes1/Excludes2, “code first” and “use additional code” notes, and add a 7th character where required.

Source: CDC/NCHS ICD-10-CM FY2027 alphabetic index.