Question 1

What is ICD-10 code G91?

Accepted Answer

G91 is the ICD-10-CM diagnosis code for hydrocephalus. G91 sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering other disorders of the nervous system (g89-g99).

Header codes like G91 cannot be reported on claims directly; they organize child codes that share clinical context. Coders should select the billable child code that matches the documented presentation and then verify its current source-backed HCC mapping. Do not infer a child code or risk adjustment value from the header alone.

Question 2

Is G91 an HCC code?

Accepted Answer

G91 is a non-billable header code. Choose the billable child code supported by the documentation, then check that child's current V28 mapping.

Question 3

Is G91 billable?

Accepted Answer

No. G91 is a header (non-billable) ICD-10-CM code. Header codes sit at a higher level of the diagnosis hierarchy and exist to organize a family of more specific child codes. Per ICD-10-CM coding guidelines, a header code cannot be reported on a claim as the diagnosis, coders must select a billable child code from the G91 hierarchy that matches the highest level of specificity supported by the provider's documentation. Payers reject header codes submitted as the primary diagnosis.

Question 4

Which HCC does G91 map to under V28?

Accepted Answer

G91 is not billable. Choose a billable child code before checking its V28 mapping.

Question 5

What RAF reference is published for G91?

Accepted Answer

G91 is not billable. Choose a billable child code before checking a V28 reference coefficient.

Question 6

What is the V28 vs V24 difference for G91?

Accepted Answer

G91 is not billable. Choose a billable child code before comparing V28 with a historical V24 reference.

Question 7

What documentation supports G91?

Accepted Answer

G91 is not billable. Choose the supported billable child code before checking mapping or documentation requirements.

HCC Buddy Code Card

G91

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What This Code Means

Includes

Excludes 1, Do NOT code together

Child Codes

Code Hierarchy

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G91 ICD-10-CM Code: Hydrocephalus