Q26.8
BillableOther congenital malformations of great veins
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is Q26.8 an HCC code?
No. Q26.8 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 Q26.8
For Q26.8to 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 Q26.8 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
Q26.8 is the ICD-10-CM diagnosis code for other congenital malformations of great veins. A birth defect affecting the structure or connections of the major veins that return blood to the heart, such as the vena cava or pulmonary veins, not classified elsewhere. Q26.8 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).
Q26.8 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 congenital venous malformations that may require complex cardiac interventions. The zero RAF weight may not account for specialized treatments and monitoring.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for Q26.8 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use this code for rare or unusual great vein malformations not captured by more specific Q26 codes
- •Ensure documentation clearly describes the anatomical abnormality to support medical necessity
Clinical Significance
Other congenital malformations of great veins encompass rare venous anomalies that can significantly impact cardiac function and venous return. These conditions often require specialized cardiac care and may be associated with complex congenital heart disease.
Documentation Requirements
- ✓Specific description of the venous malformation
- ✓Imaging studies confirming the anatomic anomaly
- ✓Assessment of hemodynamic significance
- ✓Associated congenital cardiac anomalies
- ✓Clinical symptoms and functional impact
- ✓Multidisciplinary team management plans
- ✓Surgical or interventional treatment considerations
- ✓Long-term monitoring and follow-up requirements