ICD-10 Code G91 – Hydrocephalus (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code G91 – Hydrocephalus
What it is
G91 identifies hydrocephalus, a condition involving abnormal buildup of cerebrospinal fluid in the brain’s ventricles. It is used when documentation supports hydrocephalus, whether obstructive, communicating, or unspecified.
Clinical signs
Clinical features vary by age and cause; refer to documentation. Common findings include enlarged ventricles on imaging, headache, nausea, gait disturbance, cognitive change, or signs of increased intracranial pressure.
When to use this code
Use G91 when the provider documents hydrocephalus as the diagnosis and does not specify a more detailed subcategory. It may apply to congenital, acquired, or unspecified cases when the record supports the condition. Code the documented type whenever available.
Do not use for
Do not use G91 for ventricular enlargement without a diagnosis of hydrocephalus. Check documentation if the record describes other causes of neurologic symptoms or intracranial pressure without confirming hydrocephalus.
Coding tip
Confirm whether the provider specifies the hydrocephalus type, because a more exact code may be available.