Is G91 a billable ICD-10-CM code?

No. G91 is a non-billable header code. Code to a higher level of specificity using one of its child codes.

Where does G91 sit in the tabular list?

Diseases of the nervous system (G00-G99), in the block Other disorders of the nervous system (G89-G99).

What cannot be coded together with G91?

G91 carries an Excludes1 note, which means the conditions it lists can never be coded together with it on the same encounter.

G91

G91 — Hydrocephalus

Non-billable headerICD-10-CM

G91 is a non-billable header ICD-10-CM code for hydrocephalus. It cannot be billed on its own: choose one of the more specific child codes below.

Excludes1 — never code together

These conditions cannot occur together. Billing both on the same encounter is a denial.

Arnold-Chiari syndrome with hydrocephalus (Q07.-)
congenital hydrocephalus (Q03.-)
spina bifida with hydrocephalus (Q05.-)

Includes

Conditions this code covers.

acquired hydrocephalus

Other codes that can never be billed with G91

These codes carry an Excludes1 note pointing at G91. The conflict binds both ways, but ICD-10-CM only writes it down on one side — so you would not find this by reading G91 alone.

Q03Congenital hydrocephalus
G93.2Benign intracranial hypertension
G94Other disorders of brain in diseases classified elsewhere

Risk adjustment

G91 does not map to an HCC and does not risk-adjust under CMS-HCC V28. That is normal — most ICD-10 codes do not. It still needs to be coded correctly; it just will not move a RAF score.

Code to one of these instead G91

7 child codes. Green means billable.

Questions about G91

Is G91 a billable ICD-10-CM code?: No. G91 is a non-billable header code. Code to a higher level of specificity using one of its child codes.
Where does G91 sit in the tabular list?: Diseases of the nervous system (G00-G99), in the block Other disorders of the nervous system (G89-G99).
What cannot be coded together with G91?: G91 carries an Excludes1 note, which means the conditions it lists can never be coded together with it on the same encounter.