ICD-10 Code G91.4 – Hydrocephalus in diseases classified elsewhere (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code G91.4 – Hydrocephalus in diseases classified elsewhere
What it is
G91.4 identifies hydrocephalus that occurs as a manifestation of another documented disease, condition, or injury. Use it when the chart shows the underlying cause, but the hydrocephalus itself needs separate coding.
Clinical signs
Clinical features vary; refer to documentation. Commonly, records describe ventricular enlargement, raised intracranial pressure, headache, nausea, gait change, or altered mental status, but you should code only what is documented.
When to use this code
Use G91.4 when the provider documents hydrocephalus secondary to another disorder, such as a known neurologic or infectious cause, and the record supports a causal relationship. Pair it with the underlying condition when appropriate. If the note does not clearly link the hydrocephalus to another disease, check documentation before coding.
Do not use for
Do not use this code for congenital hydrocephalus, normal pressure hydrocephalus, or hydrocephalus due to trauma unless the documentation specifically supports “in diseases classified elsewhere.” Check documentation for the correct category.
Coding tip
Always code the underlying disease first when it is documented and causally related, then add G91.4 for the hydrocephalus.