ICD-10 · PDGM grouping
G91 Hydrocephalus
All 7 codes in the G91 family, with the PDGM clinical group, comorbidity subgroup and primary-position rule CMS assigns, read from the CMS grouper crosswalk v07.2.26 and the CDC FY2027 code file.
Codes in family
7
Can lead a claim
5
Cannot lead a claim
2
What CMS assigns to G91
5 of the 7 codes group to Neuro Rehabilitation; 2 are assigned no clinical group. 1 of the 7 counts toward the Alzheimer’s disease and related dementias comorbidity subgroup; 6 are assigned none. 5 of the 7 can lead a claim. CMS attaches a code-first note to 1 of the 7.
- Alzheimer’s disease and related dementias: counts toward the high comorbidity tier only in an interaction pair.
Code first
CMS grouper convention 42, on G91.4. Code first:
- congenital syphilis (A50.4-)
- neoplasm (C00-D49)
- plasminogen deficiency (E88.02)
- underlying condition, such as:
Every code in G91
Descriptions are CDC’s FY2027 wording; where CMS’s grouper abbreviates one, its form is shown beneath.
| Code | Description | Primary position | Clinical group | Comorbidity subgroup |
|---|---|---|---|---|
| G91.0 | Communicating hydrocephalus | Can lead a claim | B | None |
| G91.1 | Obstructive hydrocephalus | Can lead a claim | B | None |
| G91.2 | (Idiopathic) normal pressure hydrocephalus | Can lead a claim | B | None |
| G91.3 | Post-traumatic hydrocephalus, unspecified | Can lead a claim | B | None |
| G91.4 | Hydrocephalus in diseases classified elsewhere | Cannot lead a claimManifestation code is not reportable as principal diagnosis | None | Alzheimer’s disease and related dementias |
| G91.8 | Other hydrocephalus | Can lead a claim | B | None |
| G91.9 | Hydrocephalus, unspecified | Cannot lead a claimPrincipal diagnosis not assigned to a clinical group | None | None |
Sources: CMS HH PPS Grouper Software v07.2.26, effective 2026-10-01, for the clinical group, comorbidity subgroup, code-first conventions and primary-position flags; CDC NCHS ICD-10-CM FY2027 code descriptions for the family title and code wording. This is the crosswalk Medicare runs a claim through. Grouping also depends on admission source, timing, the OASIS functional items and the rest of the diagnosis list.
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