ICD-10-CM 2027
ICD-10 code for hydrocephalus
From the official ICD-10-CM alphabetic index entry “Hydrocephalus (acquired) (external) (internal) (malignant) (recurrent)”. Page updated September 29, 2026.
About coding hydrocephalus
The ICD-10-CM code for hydrocephalus is G91.9 (Hydrocephalus, unspecified). The official index lists 31 more specific codes, so check the documentation for details such as type, cause, site or severity before settling on G91.9.
Within G91, choose G91.9 (unspecified) only when documentation doesn't support a more specific option: communicating hydrocephalus (G91.0), obstructive hydrocephalus (G91.1), (Idiopathic) normal pressure hydrocephalus (G91.2), post-traumatic hydrocephalus, unspecified (G91.3), in diseases classified elsewhere (G91.4) and other hydrocephalus (G91.8).
As a secondary diagnosis it is a CC (complication or comorbidity), which can move an inpatient stay into the "with CC" MS-DRG of its family, unless the principal diagnosis excludes it.
In MS-DRG v44.0, it is part of the grouping logic for DRG 056 (Degenerative Nervous System Disorders with MCC, relative weight 2.2655) and DRG 057 (Degenerative Nervous System Disorders without MCC, relative weight 1.2838), in MDC 01 (Diseases and Disorders of the Nervous System), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
More specific hydrocephalus codes (official index)
- aqueduct Sylvius stricture Q03.0 — Malformations of aqueduct of Sylvius
- causing disproportion O33.6 — Maternal care for disproportion due to hydrocephalic fetus
- with obstructed labor O66.3 — Obstructed labor due to other abnormalities of fetus
- communicating G91.0 — Communicating hydrocephalus
- congenital (external) (internal) Q03.9 — Congenital hydrocephalus, unspecified
- with spina bifida Q05.4 — Unspecified spina bifida with hydrocephalus
- cervical Q05.0 — Cervical spina bifida with hydrocephalus
- dorsal Q05.1 — Thoracic spina bifida with hydrocephalus
- lumbar Q05.2 — Lumbar spina bifida with hydrocephalus
- lumbosacral Q05.2 — Lumbar spina bifida with hydrocephalus
- sacral Q05.3 — Sacral spina bifida with hydrocephalus
- thoracic Q05.1 — Thoracic spina bifida with hydrocephalus
- thoracolumbar Q05.1 — Thoracic spina bifida with hydrocephalus
- specified NEC Q03.8 — Other congenital hydrocephalus
- due to toxoplasmosis (congenital) P37.1 — Congenital toxoplasmosis
- foramen Magendie block (acquired) G91.1 — Obstructive hydrocephalus
- congenital Q03.1 — Atresia of foramina of Magendie and Luschka
- in (due to)
- infectious disease NEC B89 — Unspecified parasitic disease
- neoplastic disease NEC (see also Neoplasm) G91.4 — Hydrocephalus in diseases classified elsewhere
- parasitic disease B89 — Unspecified parasitic disease
- newborn Q03.9 — Congenital hydrocephalus, unspecified
- with spina bifida
- noncommunicating G91.1 — Obstructive hydrocephalus
- normal pressure G91.2 — (Idiopathic) normal pressure hydrocephalus
- secondary G91.0 — Communicating hydrocephalus
- obstructive G91.1 — Obstructive hydrocephalus
- otitic G93.2 — Benign intracranial hypertension
- post-traumatic NEC G91.3 — Post-traumatic hydrocephalus, unspecified
- secondary G91.4 — Hydrocephalus in diseases classified elsewhere
- post-traumatic G91.3 — Post-traumatic hydrocephalus, unspecified
- specified NEC G91.8 — Other hydrocephalus
- syphilitic, congenital A50.49 — Other late congenital neurosyphilis
Common questions about hydrocephalus ICD-10 codes
What is the ICD-10 code for hydrocephalus?
- G91.9 — Hydrocephalus, unspecified. More specific codes apply when the documentation supports them: Q03.0, O33.6, O66.3, G91.0 and others below.
What is the ICD-10 code for aqueduct sylvius stricture hydrocephalus?
- Q03.0 — Malformations of aqueduct of Sylvius.
What is the ICD-10 code for causing disproportion hydrocephalus?
- O33.6 — Maternal care for disproportion due to hydrocephalic fetus (header code; choose a more specific subcode).
What is the ICD-10 code for communicating hydrocephalus?
- G91.0 — Communicating hydrocephalus.
What is the ICD-10 code for congenital hydrocephalus?
- Q03.9 — Congenital hydrocephalus, unspecified.
What is the ICD-10 code for foramen magendie block hydrocephalus?
- G91.1 — Obstructive hydrocephalus.
What is the ICD-10 code for newborn hydrocephalus?
- Q03.9 — Congenital hydrocephalus, unspecified.
Is G91.9 billable?
- Yes. G91.9 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can G91.9 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict G91.9 as a principal diagnosis.
Is G91.9 a CC or MCC?
- G91.9 is a CC (complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.