K51.90 ICD-10-CM Code: Ulcerative colitis, unspecified, without complications
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 / Diseases of the digestive system (K00-K95) / Noninfective enteritis and colitis (K50-K52)
K51.90
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceUlcerative colitis, unspecified, without complications
Ulcerative colitis of unspecified extent without any complications.
Buddy Insight
Ulcerative colitis, unspecified, without complications is used when ulcerative colitis is diagnosed but the anatomic extent is not documented.
CMS-HCC V28
MappedHCC 81
RAF 0.0
CMS-HCC V24
MappedHCC 35
RAF 0.289
ACA/HHS
00
RAF 0
ESRD/PACE
MappedHCC 35
RAF 0.0
RXHCC
MappedHCC 67
RAF 0.0
Code Trumping
Basket needed
Code Book Path
Inclusion Terms
OfficialICD-10-CM does not list inclusion terms for K51.90 in this effective period.
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for K51.90 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for K51.90 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for K51.90 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for K51.90 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for K51.90 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for K51.90 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 K51.90 an HCC code?
Yes. K51.90 maps to Ulcerative Colitis under the CMS-HCC V28 risk adjustment model (and Inflammatory Bowel Disease 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 K51.90
For K51.90to 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 K51.90 during that encounter, not just copy-forwarded from a problem list.
What This Code Means
K51.90 is the ICD-10-CM diagnosis code for ulcerative colitis, unspecified, without complications. Ulcerative colitis of unspecified extent without any complications. K51.90 sits in the ICD-10-CM chapter for diseases of the digestive system (k00-k95), within the section covering noninfective enteritis and colitis (k50-k52).
Under the CMS-HCC V28 risk adjustment model, K51.90 maps to Ulcerative Colitis (HCC 81) with a community, non-dual, aged base RAF weight of 0.000. Under the older CMS-HCC V24 model, K51.90 maps to Inflammatory Bowel Disease (HCC 35) with a community, non-dual, aged base RAF weight of 0.289. 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 a default code when the extent of ulcerative colitis is not documented; query for disease extent (proctitis, left-sided, pancolitis) if possible. Because K51.90 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 K51.90 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This is a default code when the extent of ulcerative colitis is not documented; query for disease extent (proctitis, left-sided, pancolitis) if possible.
- •Use only when no complications are present; if any complication exists, select the appropriate K51.91x code instead.
Clinical Significance
Ulcerative colitis, unspecified, without complications is used when ulcerative colitis is diagnosed but the anatomic extent is not documented. While this code captures the fundamental diagnosis, it represents a missed opportunity for specificity. The anatomic extent of ulcerative colitis directly impacts treatment decisions, cancer surveillance intervals, and prognosis.
Documentation Requirements
- ✓Confirmed diagnosis of ulcerative colitis
- ✓Documentation that extent cannot be determined from available records
- ✓Statement confirming no complications are present
- ✓Treatment plan appropriate for ulcerative colitis
- ✓Plan for colonoscopy to determine disease extent if not yet performed
- ✓Evidence of provider query for disease extent if available
Commonly Confused Codes
- •K51.90 vs K51.00/K51.20/K51.30/K51.50: Use anatomically specific codes when extent is documented
- •K51.90 vs K52.9: K52.9 is noninfective colitis unspecified (not necessarily ulcerative colitis)
- •K51.90 vs K51.80: K51.80 is 'other' ulcerative colitis (known but non-standard); K51.90 is truly unspecified
- •K51.90 vs K50.90: K50.90 is Crohn disease unspecified; these are different diseases