What does ICD-10 code G91 mean?

ICD-10 code G91 is the standardized code used for hydrocephalus in medical records and coding systems.

When is ICD-10 code G91 used?

Doctors, hospitals, and insurers may use ICD-10 code G91 when recording hydrocephalus in a standardized format. This entry may also act as a broader category that points toward more specific child codes.

Does ICD-10 code G91 confirm a diagnosis?

No. A code helps standardize documentation and claims, but it should not be read as a substitute for a clinician's full assessment.

ICD10

ICD-10 Code G91: Hydrocephalus

Name: ICD-10 Code G91: Hydrocephalus
Creator: HealthAssure Clinical Team
Published: 2026-05-21T06:07:19.583Z

G91 is an ICD-10 diagnosis entry used to group records related to Hydrocephalus. You may see this entry in coding references, medical records, or claims workflows when a broader diagnosis category is being reviewed before a more specific code is chosen. ICD-10 entries help standardize how diagnoses are organized for coding, reporting, analytics, and documentation. This code sits within the broader ICD-10 area for Diseases of the nervous system (G00-G99).

Reviewed by HealthAssure Clinical TeamUpdated 21 May 2026

What is this code?

ICD-10 entries help standardize how diagnoses are organized for coding, reporting, analytics, and documentation. This code sits within the broader ICD-10 area for Diseases of the nervous system (G00-G99).

When is it used?

May be used when a clinician documents hydrocephalus in a patient's medical record.
May appear in hospital records, claims, referrals, and clinical documentation.
This code may act more like a grouping or parent code, so a more specific child code may be used in final documentation when available.

What it does not mean

A code alone does not explain severity, treatment plan, or outcome.
A medical code should not be treated as a substitute for a doctor's diagnosis or advice.
This entry may represent a broader category rather than the most specific billable code.

Code hierarchy

chapter

6Diseases of the nervous system (G00-G99)

block

G89-G99Other disorders of the nervous system

currentG89-G99

Official coding notes

Includes

acquired hydrocephalus

Excludes1 (do not code together)

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

Where you may see this code

You may see this entry in coding references, medical records, or claims workflows when a broader diagnosis category is being reviewed before a more specific code is chosen.

Related specialists

NeurologistGeneral Physician

Sibling codes

G89Pain, not elsewhere classified G90Disorders of autonomic nervous system G92Toxic encephalopathy G93Other disorders of brain G94Other disorders of brain in diseases classified elsewherebillable G95Other and unspecified diseases of spinal cord G96Other disorders of central nervous system G97Intraoperative and postprocedural complications and disorders of nervous system, not elsewhere classified G98Other disorders of nervous system not elsewhere classified G99Other disorders of nervous system in diseases classified elsewhere

Coding guidelines

Compatibility

Legacy code aligns to an official FY 2026 category. Frontend should resolve to the official category page and surface the billable child codes.

Legacy codes

G91

Replacement codes

G91.0 — Communicating hydrocephalusG91.1 — Obstructive hydrocephalusG91.2 — (Idiopathic) normal pressure hydrocephalusG91.3 — Post-traumatic hydrocephalus, unspecifiedG91.4 — Hydrocephalus in diseases classified elsewhereG91.8 — Other hydrocephalusG91.9 — Hydrocephalus, unspecified

Common synonyms

Hydrocephalus

Frequently asked questions

About this content

This page is prepared by HealthAssure's clinical team using official coding standards from ICD-10. AI tools assist with drafting explanations, which are then reviewed and verified by healthcare professionals for accuracy. This content is for informational purposes and does not replace professional medical advice. Meet our team.