2027 ICD-10-CM Diagnosis Code G91Hydrocephalus

ICD-10-CM Codes›G00–G99›G89-G99›G91

ICD-10-CM G91
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

G91 is a non-billable ICD-10-CM category code for hydrocephalus, so it cannot be submitted on claims. Use a more specific code from this category instead, such as G91.0, G91.1, G91.2, and G91.3.

Code Identity

ICD-10-CM Code
G91
Billable Status
No — Non-Billable Category
Code Describes
Hydrocephalus
Short Description
Hydrocephalus
Same as the full description in the CMS dataset.
Chapter
G89-G99
Other disorders of the nervous system

Code Classification

ChapterG00–G99Diseases of the nervous system
SectionG89-G99Other disorders of the nervous system
CategoryG91Hydrocephalus
This CodeG91Hydrocephalus

Specific Coding for HydrocephalusOverview

Non-specific codes like G91 require more characters. Use one of these billable codes instead:

  • Use G91.0 for Communicating hydrocephalus

  • Use G91.1 for Obstructive hydrocephalus

  • Use G91.2 for (Idiopathic) normal pressure hydrocephalus

  • Use G91.3 for Post-traumatic hydrocephalus, unspecified

  • Use G91.4 for Hydrocephalus in diseases classified elsewhere

  • Use G91.8 for Other hydrocephalus

  • Use G91.9 for Hydrocephalus, unspecified

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to G91: its own notes plus those printed at Chapter 6. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

  • acquired hydrocephalus

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

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

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Chapter 6 (G00-G99) Diseases of the nervous system applies to 700 codes
  • certain conditions originating in the perinatal period (P04-P96)
  • certain infectious and parasitic diseases (A00-B99)
  • complications of pregnancy, childbirth and the puerperium (O00-O9A)
  • congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
  • endocrine, nutritional and metabolic diseases (E00-E88)
  • injury, poisoning and certain other consequences of external causes (S00-T88)
  • neoplasms (C00-D49)
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name G91, its category, or a range that includes it.

Excludes1 1

These codes carry an Excludes1 note naming G91: they are not reported together with it, unless the two conditions are unrelated.

  • Q03 Congenital hydrocephalus
    acquired hydrocephalus (G91.-)

Clinical InformationClinical

  • Hydrocephalus

    excessive accumulation of cerebrospinal fluid within the cranium which may be associated with dilation of cerebral ventricles, intracranial hypertension; headache; lethargy; urinary incontinence; and ataxia.

Patient EducationClinical

Hydrocephalus

Hydrocephalus is the buildup of too much cerebrospinal fluid in the brain. Normally, this fluid cushions your brain. When you have too much, though, it puts harmful pressure on your brain.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About G91Overview

What is the ICD-10 code for hydrocephalus?

G91 is the ICD-10-CM category for hydrocephalus, but it is a non-billable header: claims need a more specific code from this category, listed on this page.

Is G91 (Hydrocephalus) a billable code?

No. This is a category header that groups the codes for hydrocephalus, and headers cannot be submitted on claims. Claims for hydrocephalus need a more specific code from this category, such as G91.0, G91.1, and G91.2.

Can G91 be reported with a code from Q07?

Not as a rule. The Excludes1 note on G91 lists "Arnold-Chiari syndrome with hydrocephalus (Q07.-)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).