P77.9 ICD-10-CM Code: Necrotizing enterocolitis in newborn, unspecified
HCC Buddy Code Card
Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.
FY 2026 Apr update / Certain conditions originating in the perinatal period (P00-P96) / Digestive system disorders of newborn (P76-P78)
P77.9
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceNecrotizing enterocolitis in newborn, unspecified
Necrotizing enterocolitis in a newborn where the specific stage or severity level is not documented or cannot be determined.
Buddy Insight
Unspecified NEC indicates the presence of necrotizing enterocolitis but lacks the specific staging information crucial for treatment planning and prognosis.
CMS-HCC V28
MappedHCC 78
RAF 0.0
CMS-HCC V24
00
RAF 0
ACA/HHS
00
RAF 0
ESRD/PACE
00
RAF 0
RXHCC
00
RAF 0
Code Trumping
Basket needed
Code Book Path
Inclusion Terms
Official- Necrotizing enterocolitis in newborn, NOS
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for P77.9 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for P77.9 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for P77.9 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for P77.9 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for P77.9 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for P77.9 in this effective period.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.
Is P77.9 an HCC code?
Yes. P77.9 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 P77.9
For P77.9to 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 P77.9 during that encounter, not just copy-forwarded from a problem list.
What This Code Means
P77.9 is the ICD-10-CM diagnosis code for necrotizing enterocolitis in newborn, unspecified. Necrotizing enterocolitis in a newborn where the specific stage or severity level is not documented or cannot be determined. P77.9 sits in the ICD-10-CM chapter for certain conditions originating in the perinatal period (p00-p96), within the section covering digestive system disorders of newborn (p76-p78).
Under the CMS-HCC V28 risk adjustment model, P77.9 maps to Intestinal Obstruction/Perforation (HCC 78) with a community, non-dual, aged base RAF weight of 0.000. P77.9 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 only when stage cannot be determined from documentation; query the provider for stage information (1, 2, or 3) to assign a more specific code. Because P77.9 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 P77.9 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use only when stage cannot be determined from documentation; query the provider for stage information (1, 2, or 3) to assign a more specific code
- •Review imaging reports and clinical notes for evidence of pneumatosis, perforation, or other staging criteria
Clinical Significance
Unspecified NEC indicates the presence of necrotizing enterocolitis but lacks the specific staging information crucial for treatment planning and prognosis. This diagnosis still represents a serious neonatal condition requiring intensive monitoring and management.
Documentation Requirements
- ✓Clinical evidence of necrotizing enterocolitis
- ✓Radiographic abnormalities consistent with NEC
- ✓Treatment interventions appropriate for NEC
- ✓Gestational age and risk factor documentation
- ✓Attempts to determine staging if possible
- ✓Reason why specific staging cannot be determined
- ✓Monitoring and management protocols implemented
- ✓Follow-up plans for disease progression assessment
Commonly Confused Codes
- •P77.1 — Stage 1 necrotizing enterocolitis (specific early stage documented)
- •P77.2 — Stage 2 necrotizing enterocolitis (pneumatosis intestinalis present)
- •P77.3 — Stage 3 necrotizing enterocolitis (perforation and peritonitis present)
- •P78.3 — Other necrotizing enterocolitis (atypical or non-standard presentation)