ICD-10 Code G91.1 – Obstructive Hydrocephalus (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code G91.1 – Obstructive hydrocephalus
What it is
Obstructive hydrocephalus is a buildup of cerebrospinal fluid caused by a blockage in the normal flow pathway within the brain. You use this code when the record identifies hydrocephalus from obstruction rather than another cause.
Clinical signs
Clinical features vary; refer to documentation. Common findings may include enlarged ventricles on imaging, headache, nausea, vomiting, gait disturbance, or signs of raised intracranial pressure.
When to use this code
Use G91.1 when the provider documents obstructive, noncommunicating, or blocked-flow hydrocephalus. It is appropriate when imaging or operative notes support ventricular enlargement due to an anatomic obstruction. Check documentation if the cause is congenital, postprocedural, or due to another specified condition.
Do not use for
Do not use this code for communicating hydrocephalus, normal pressure hydrocephalus, or hydrocephalus from another specifically documented cause. If the chart only says “hydrocephalus” without type, check documentation.
Coding tip
Look for the provider’s exact type of hydrocephalus and the obstructing cause, because that wording determines whether G91.1 is correct.