Q42.8
BillableCongenital absence, atresia and stenosis of other parts of large intestine
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is Q42.8 an HCC code?
Yes. Q42.8 maps to Intestinal Obstruction/Perforation under the CMS-HCC V28 risk adjustment model.
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 Q42.8
For Q42.8 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 Q42.8 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
Q42.8 is the ICD-10-CM diagnosis code for congenital absence, atresia and stenosis of other parts of large intestine. A birth defect involving absence, closure, or abnormal narrowing of other specified parts of the large intestine (colon) not covered by the more specific codes. Q42.8 sits in the ICD-10-CM chapter for congenital malformations, deformations, chromosomal abnormalities, and genetic disorders (q00-qa0), within the section covering other congenital malformations of the digestive system (q38-q45).
Under the CMS-HCC V28 risk adjustment model, Q42.8 maps to Intestinal Obstruction/Perforation (HCC 78) with a community, non-dual, aged base RAF weight of 0.000. Q42.8 was not retained as a payment HCC under the older V24 model, so V28 introduced or recategorized it during the 2024–2026 phase-in. 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.
Use this code for defects of the colon, cecum, or other large intestine segments not specified in Q42.0-Q42.3. Because Q42.8 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 Q42.8 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
Clinical Significance
This congenital malformation represents a significant structural abnormality requiring lifelong medical management and potential surgical intervention. These patients often require specialized gastroenterology care and may need complex reconstructive procedures, making accurate coding essential for care coordination and resource allocation.
Documentation Requirements
- ✓Specific anatomical location of the absence, atresia, or stenosis within the large intestine
- ✓Whether the condition is complete absence, partial atresia, or stenosis
- ✓Associated complications or comorbidities
- ✓Surgical interventions performed or planned
- ✓Current functional status of the digestive system
- ✓Evidence of congenital nature (present from birth)
- ✓Any associated genetic syndromes or chromosomal abnormalities