ICD-10-CM 2027
ICD-10 code for secondary hydrocephalus
Hydrocephalus in diseases classified elsewhere
From the official ICD-10-CM alphabetic index entry “Hydrocephalus (acquired) (external) (internal) (malignant) (recurrent) › secondary”. Page updated September 29, 2026.
About coding secondary hydrocephalus
The ICD-10-CM code for secondary hydrocephalus is G91.4 (Hydrocephalus in diseases classified elsewhere). The official index lists 1 more specific code, so check the documentation for details such as type, cause, site or severity before settling on G91.4.
Within G91 (hydrocephalus), G91.4 is specifically for hydrocephalus in diseases classified elsewhere. Related codes cover communicating hydrocephalus (G91.0), obstructive hydrocephalus (G91.1), (Idiopathic) normal pressure hydrocephalus (G91.2), post-traumatic hydrocephalus, unspecified (G91.3), other hydrocephalus (G91.8) and unspecified (G91.9).
Don't report G91.4 together with the conditions in its Excludes1 note: hydrocephalus due to congenital toxoplasmosis (P37.1).
Code first underlying condition, such as: congenital syphilis (A50.4-), neoplasm (C00-D49) and plasminogen deficiency (E88.02).
More specific secondary hydrocephalus codes (official index)
- post-traumatic G91.3 — Post-traumatic hydrocephalus, unspecified
Don't confuse with (Excludes1 for G91.4)
- hydrocephalus due to congenital toxoplasmosis (P37.1)
Common questions about secondary hydrocephalus ICD-10 codes
What is the ICD-10 code for secondary hydrocephalus?
- G91.4 — Hydrocephalus in diseases classified elsewhere. More specific codes apply when the documentation supports them: G91.3.
What is the ICD-10 code for post-traumatic secondary hydrocephalus?
- G91.3 — Post-traumatic hydrocephalus, unspecified.
Is G91.4 billable?
- Yes. G91.4 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can G91.4 be used as a principal diagnosis?
- No. It is a manifestation code, so it describes the effect of an underlying disease and can't be the principal diagnosis. Code the underlying condition first.
Is G91.4 a CC or MCC?
- No. G91.4 is neither a CC nor an MCC under MS-DRG v44.0.