Q26.4
BillableAnomalous pulmonary venous connection, unspecified
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is Q26.4 an HCC code?
No. Q26.4 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.
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 Q26.4
For Q26.4to 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 Q26.4 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
Q26.4 is the ICD-10-CM diagnosis code for anomalous pulmonary venous connection, unspecified. A birth defect where pulmonary veins (veins returning blood from the lungs) connect abnormally, but the specific pattern or extent of the abnormality is not specified. Q26.4 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 circulatory system (q20-q28).
Q26.4 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.
This code maps to HCC 191 (Obesity) in the RxHCC model with RAF 0.0, which appears to be an incorrect mapping as this represents a congenital cardiac anomaly potentially requiring complex intervention. The zero RAF weight may underestimate the resource utilization for cardiac care.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for Q26.4 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use this code only when the type of anomalous pulmonary venous connection cannot be determined
- •Query the provider for clarification on whether the connection is total or partial if documentation is unclear
Clinical Significance
Unspecified anomalous pulmonary venous connection indicates the presence of abnormal pulmonary venous drainage but lacks the specific anatomic detail crucial for treatment planning. This condition still represents a potentially serious cardiac anomaly requiring specialized management.
Documentation Requirements
- ✓Evidence of abnormal pulmonary venous drainage pattern
- ✓Attempts to characterize the specific anomaly type
- ✓Clinical significance and hemodynamic impact
- ✓Associated cardiac anomalies assessment
- ✓Reason why specific type cannot be determined
- ✓Cardiac catheterization or advanced imaging results
- ✓Treatment planning despite incomplete characterization
- ✓Cardiothoracic surgery consultation documentation
Commonly Confused Codes
- •Q26.2 — Total anomalous pulmonary venous connection (all veins, specific type)
- •Q26.3 — Partial anomalous pulmonary venous connection (some veins, specific type)
- •Q26.8 — Other congenital malformations of great veins (different venous structures)
- •Q21.1 — Atrial septal defect (may be associated but different primary defect)