Q03.9
BillableCongenital hydrocephalus, unspecified
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is Q03.9 an HCC code?
Yes. Q03.9 maps to Spinal Cord Disorders/Injuries under the CMS-HCC V28 risk adjustment model (and Spinal Cord Disorders/Injuries under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for Q03.9
For Q03.9 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically — it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed Q03.9 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
Q03.9 is the ICD-10-CM diagnosis code for congenital hydrocephalus, unspecified. A birth defect involving fluid buildup in the brain when the specific cause or type is not documented or identified. Q03.9 sits in the ICD-10-CM chapter for congenital malformations, deformations, chromosomal abnormalities, and genetic disorders (q00-qa0), within the section covering congenital malformations of the nervous system (q00-q07).
Under the CMS-HCC V28 risk adjustment model, Q03.9 maps to Spinal Cord Disorders/Injuries (HCC 182) with a community, non-dual, aged base RAF weight of 0.282. Under the older V24 model, Q03.9 mapped to the same category but with a base RAF weight of 0.464 — V28 recalibrated weights across the entire model. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
This is the least specific code; use only when the type of hydrocephalus cannot be determined. Because Q03.9 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for Q03.9 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This is the least specific code; use only when the type of hydrocephalus cannot be determined
- •Query the provider if additional diagnostic information is available to assign a more specific Q03 code
Clinical Significance
Unspecified congenital hydrocephalus indicates CSF accumulation present from birth when the specific underlying cause or mechanism is not determined. This condition still requires the same intensive management and monitoring as other forms of congenital hydrocephalus.
Documentation Requirements
- ✓Documentation of hydrocephalus present from birth or early infancy
- ✓Evidence of cerebrospinal fluid accumulation without specific cause identified
- ✓Neuroimaging showing ventricular dilation
- ✓Clinical presentation consistent with congenital hydrocephalus
- ✓Documentation that specific type or cause is unspecified
- ✓Treatment interventions and surgical history
- ✓Neurological and developmental assessments
- ✓Ongoing care and monitoring requirements