K51.918 ICD-10-CM Code: Ulcerative colitis, unspecified with other complication
K51.918 maps to CMS-HCC V28 81. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC coding software
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FY 2026 Apr update / Diseases of the digestive system (K00-K95) / Noninfective enteritis and colitis (K50-K52)
K51.918
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceUlcerative colitis, unspecified with other complication
Ulcerative colitis of unspecified extent with a complication other than bleeding, obstruction, fistula, or abscess.
Buddy Insight
Ulcerative colitis, unspecified, with other complication captures a known non-standard complication of ulcerative colitis when the anatomic extent is undetermined.
CMS-HCC V28
MappedHCC 81
Coefficient HCC 81: 0.244 (Community Non-Dual Aged (CNA))
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
MappedHCC 048
Code-level coefficient reference
ESRD/PACE
MappedHCC 35
Code-level coefficient reference
RXHCC
MappedHCC 67
Code-level coefficient reference
Code Book Path
Inclusion Terms
OfficialNo inclusion terms are included in this display for K51.918. Check the code and parent instructions in the Code Book.
Excludes 2
Official- certain conditions originating in the perinatal period (P04-P96)Inherited from K00-K95
- certain infectious and parasitic diseases (A00-B99)Inherited from K00-K95
- complications of pregnancy, childbirth and the puerperium (O00-O9A)Inherited from K00-K95
- congenital malformations, deformations and chromosomal abnormalities (Q00-Q99)Inherited from K00-K95
- endocrine, nutritional and metabolic diseases (E00-E88)Inherited from K00-K95
- injury, poisoning and certain other consequences of external causes (S00-T88)Inherited from K00-K95
- neoplasms (C00-D49)Inherited from K00-K95
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)Inherited from K00-K95
Related Codes
Includes
Official- noninfective inflammatory bowel diseaseInherited from K50-K52
Excludes 1
Official- irritable bowel syndrome (K58.-)Inherited from K50-K52, K51
- megacolon (K59.3-)Inherited from K50-K52, K51
- Crohn's disease [regional enteritis] (K50.-)Inherited from K50-K52, K51
Code First
OfficialNo Code First sequencing instructions are included in this display for K51.918. Check the code and parent instructions in the Code Book.
Use Additional
Official- code to identify any associated fistulas, if applicable:Inherited from K51
- anal fistula (K60.3-)Inherited from K51
- anorectal fistula (K60.5-)Inherited from K51
- rectal fistula (K60.4-)Inherited from K51
- code to identify manifestations, such as:Inherited from K51
- pyoderma gangrenosum (L88)Inherited from K51
Code Also
OfficialNo Code Also instructions are included in this display for K51.918. Check the code and parent instructions in the Code Book.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
Is K51.918 an HCC code?
Yes. K51.918 (Ulcerative colitis, unspecified with other complication) maps to HCC 81, Ulcerative Colitis under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.244. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.
Coder answer: K51.918 is billable and maps to V28 HCC 81, Ulcerative Colitis. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- K51.918
- Description
- Ulcerative colitis, unspecified with other complication
- HCC (V28)
- HCC 81 — Ulcerative Colitis
- RAF reference coefficient
- 0.244
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.
Work K51.918 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT review for K51.918
For K51.918, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.
- 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
Coder workflow notes
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What This Code Means
K51.918 is the ICD-10-CM diagnosis code for ulcerative colitis, unspecified with other complication. Ulcerative colitis of unspecified extent with a complication other than bleeding, obstruction, fistula, or abscess. K51.918 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, K51.918 maps to Ulcerative Colitis (HCC 81) with a source-labeled community, non-dual, aged reference coefficient of 0.244. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.
Use K51.918 when the provider wording supports ulcerative colitis, unspecified with other complication. Check the FY2026 tabular notes and the full code path before the final code choice. For K51.918, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. 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, source-labeled coefficient references, and MEAT documentation criteria for K51.918 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use K51.918 when the provider wording supports ulcerative colitis, unspecified with other complication. Check the FY2026 tabular notes and the full code path before the final code choice.
- •For this DOS, capture the provider's current assessment and the care action documented for ulcerative colitis, unspecified with other complication. Keep the checklist tied to the note.
- •Do not swap K51.918 with K51.911. The FY2026 tabular describes K51.911 as ulcerative colitis, unspecified with rectal bleeding. Follow the documented detail.
- •The FY2026 Alphabetic Index routes Colitis (acute) (catarrhal) (chronic) (noninfective) (hemorrhagic) under ulcerative (chronic) with complication > specified complication NEC to K51.918. Confirm that the indexed wording matches the provider documentation before using this route.
- •Ask Buddy to show the official notes for K51.918 or compare its code path with K51.911.
Clinical Significance
Ulcerative colitis, unspecified, with other complication captures a known non-standard complication of ulcerative colitis when the anatomic extent is undetermined. This code requires two levels of clarification: the disease extent and the specific complication details, making it important to query the provider for both data points.
Documentation Requirements
- ✓Confirmed ulcerative colitis diagnosis
- ✓Clear documentation of the specific complication
- ✓Provider statement linking complication to the colitis
- ✓Treatment plan for both the colitis and the complication
- ✓Plan to determine disease extent
- ✓Disease activity assessment