DxCodebookFY2027 · Oct 1, 2026 – Sep 30, 2027

Category · FY2027

G91 Hydrocephalus

  • Header · not billable

G91 is not billable. The category heads 7 billable codes in FY2027: the 7 codes directly below it.

Index → code

  • Hydrocephalus (acquired) (external) (internal) (malignant) (recurrent) → G91.9
  • Occlusion, occludedaqueduct of Sylvius → G91.1
  • Occlusion, occludedventricle (brain) NEC → G91.1

Where it sits

  1. Chapter 6 Diseases of the nervous system (G00-G99)
  2. G89-G99 Other disorders of the nervous system (G89-G99)
  3. G91 Hydrocephalus
Billable codes
7
Subdivisions
7
CC / MCC codes
6 / 0
HCC V28 codes
7
New FY2027
0
Index entries
20

Codes in G91

  1. G91.0
    Communicating hydrocephalus
    BillableCC127
    Inclusion terms 1

    Inclusion terms

    • Secondary normal pressure hydrocephalus
  2. G91.1
    Obstructive hydrocephalus
    BillableCC127
  3. G91.2
    (Idiopathic) normal pressure hydrocephalus
    BillableCC127
    Inclusion terms 1

    Inclusion terms

    • Normal pressure hydrocephalus NOS
  4. G91.3
    Post-traumatic hydrocephalus, unspecified
    BillableCC127
  5. G91.4
    Hydrocephalus in diseases classified elsewhere
    Billable127
    Excludes1 1, Code first 4

    Excludes1

    • hydrocephalus due to congenital toxoplasmosis (P37.1) P37.1

    Code first

    • underlying condition, such as:
    • congenital syphilis (A50.4-) A50.4
    • neoplasm (C00-D49) C00 D49
    • plasminogen deficiency (E88.02) E88.02
  6. G91.8
    Other hydrocephalus
    BillableCC127
  7. G91.9
    Hydrocephalus, unspecified
    BillableCC127

CC/MCC: as a secondary diagnosis, unless the principal diagnosis is on the code’s PDX exclusion list (MS-DRG v44 Appendix C; list on the code card).

Sources of each column.

Instructions

At G91

Includes

  • acquired hydrocephalus

Excludes1

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

Notes that also apply

Chapter 6 instructions (Excludes2 8): printed on the chapter 6 page.

Index entries

  • Hydrocephalus (acquired) (external) (internal) (malignant) (recurrent) → G91.9
  • Hydrocephalus (acquired) (external) (internal) (malignant) (recurrent)communicating → G91.0
  • Block, blockedforamen Magendie (acquired) → G91.1
  • Hydrocephalus (acquired) (external) (internal) (malignant) (recurrent)foramen Magendie block (acquired) → G91.1
  • Hydrocephalus (acquired) (external) (internal) (malignant) (recurrent)noncommunicating → G91.1
  • Hydrocephalus (acquired) (external) (internal) (malignant) (recurrent)obstructive → G91.1
  • Obstruction, obstructed, obstructiveaqueduct of Sylvius → G91.1
  • Occlusion, occludedaqueduct of Sylvius → G91.1
  • Occlusion, occludedventricle (brain) NEC → G91.1
  • Hydrocephalus (acquired) (external) (internal) (malignant) (recurrent)normal pressure → G91.2
  • Hydrocephalus (acquired) (external) (internal) (malignant) (recurrent)post-traumatic NEC → G91.3
  • Hydrocephalus (acquired) (external) (internal) (malignant) (recurrent)secondary → G91.4
  • Hydrocephalus (acquired) (external) (internal) (malignant) (recurrent)specified NEC → G91.8
  • Hydrocephalus (acquired) (external) (internal) (malignant) (recurrent)in (due to)infectious disease NEC → B89 [G91.4]
  • Hydrocephalus (acquired) (external) (internal) (malignant) (recurrent)in (due to)parasitic disease → B89 [G91.4]
  • Hydrocephalus (acquired) (external) (internal) (malignant) (recurrent)normal pressuresecondary → G91.0
  • Stenosis, stenotic (cicatricial)aqueduct of Sylvius (congenital)acquired → G91.1
  • Strictureaqueduct of Sylvius (congenital)acquired → G91.1
  • Hydrocephalus (acquired) (external) (internal) (malignant) (recurrent)secondarypost-traumatic → G91.3
  • Hydrocephalus (acquired) (external) (internal) (malignant) (recurrent)in (due to)neoplastic disease NEC (see also Neoplasm) → G91.4

NCHS Alphabetic Index. Index first, then the Tabular List.

Hierarchy