ICD-10 Code G91.9 – Hydrocephalus, unspecified (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code G91.9 – Hydrocephalus, unspecified
What it is
G91.9 identifies hydrocephalus when the record does not specify the type or cause. Use it for documented ventricular enlargement or cerebrospinal fluid buildup without a more precise diagnosis.
Clinical signs
Clinical features vary; refer to documentation. Commonly noted findings include enlarged ventricles on imaging and signs of increased intracranial pressure, but the chart must support hydrocephalus.
When to use this code
Use G91.9 when the provider documents hydrocephalus but does not state whether it is obstructive, communicating, congenital, or another defined form. It also fits cases where the evaluation is incomplete and the record remains nonspecific.
Choose this code only when the diagnosis is established in the note, imaging report, or discharge summary. If the documentation later specifies a type or underlying cause, code the more detailed diagnosis instead.
Do not use for
Do not use G91.9 for documented congenital hydrocephalus, normal pressure hydrocephalus, or hydrocephalus due to a known cause when a more specific code is available. Check documentation.
Coding tip
Query the provider when the record says only “hydrocephalus” and the type, cause, or acuity is missing.