What is ICD-10 code K51.80?

K51.80 is the ICD-10-CM diagnosis code for Other ulcerative colitis without complications. A form of ulcerative colitis affecting areas of the colon other than the left side, without any complications. It belongs to the ICD-10-CM chapter for diseases of the digestive system (k00-k95). K51.80 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. K51.80 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. K51.80 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. K51.80 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

Which HCC does K51.80 map to under V28?

K51.80 maps to CMS-HCC V28 HCC 81 (Ulcerative Colitis). The category numbers, labels, and conditions come from the CMS-HCC V28 model file for payment year 2026.

2026 ICD-10-CM K51.80: Other ulcerative colitis

K51.80 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 Buddy coding tools

ICD-10-CM Code View

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Code lookupK51.80

Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the digestive system (K00-K95) / Noninfective enteritis and colitis (K50-K52)

K51.80

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Other ulcerative colitis without complications

A form of ulcerative colitis affecting areas of the colon other than the left side, without any complications.

Buddy Insight

Overview Risk Models Code Book Documentation Audit Notes Edition comparison

CMS-HCC V28

Mapped

HCC 81

Ulcerative Colitis

Code-level coefficient reference

CMS-HCC V24

Historical

Not used for standard CY2026 Medicare Advantage payment. Select a historical period to review V24.

Not used for CY2026 payment

ACA/HHS

Mapped

HCC 048

HHS-HCC 048 adult, RAF varies...

Code-level coefficient reference

ESRD/PACE

Mapped

HCC 35

Inflammatory Bowel Disease

Code-level coefficient reference

RXHCC

Mapped

HCC 67

Inflammatory Bowel Disease

Code-level coefficient reference

Code Book Path

Official

K51Ulcerative colitis K51.8Other ulcerative colitis K51.80Other ulcerative colitis without complications

Inclusion Terms

Official

No inclusion terms are included in this display for K51.80. 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

Official

K51.81Other ulcerative colitis with complications

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

Official

No Code First sequencing instructions are included in this display for K51.80. 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

Official

No Code Also instructions are included in this display for K51.80. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance

Confirmed ulcerative colitis diagnosis via colonoscopy and biopsy

Documentation of the specific extent or type of colitis that does not fit standard subcategories

Statement confirming no complications are present

Current treatment plan and disease management approach

MEAT Support

HCC Buddy guidance

Confirmed ulcerative colitis diagnosis via colonoscopy and biopsy

Documentation of the specific extent or type of colitis that does not fit standard subcategories

Statement confirming no complications are present

Current treatment plan and disease management approach

Audit Caution

HCC Buddy guidance

Using this code when a more anatomically specific code (pancolitis, proctitis, etc.) is appropriate

Confusing 'other' ulcerative colitis with 'unspecified' ulcerative colitis

Not querying for anatomic extent when colonoscopy reports are available

Failing to verify absence of complications before assigning this code

Common Mistakes

HCC Buddy guidance

K51.80 vs K51.00/K51.20/K51.30/K51.50 — Use anatomically specific codes when extent is clearly documented

K51.80 vs K51.90 — K51.90 is ulcerative colitis unspecified; K51.80 is for identified 'other' types

K51.80 vs K52.9 — K52.9 is noninfective colitis unspecified; K51.80 is specifically ulcerative colitis

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 K51.80 an HCC code?

Yes. K51.80 (Other ulcerative colitis without complications) 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: K51.80 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: K51.80
Description: Other ulcerative colitis without complications
HCC (V28): HCC 81 — Ulcerative Colitis
RAF reference coefficient: 0.244
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 81, Ulcerative Colitis

0.244

ESRDHCC 35, Inflammatory Bowel Disease

Not separately weighted

RxHCCHCC 67, Inflammatory Bowel Disease

Not separately weighted

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 K51.80 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for K51.80

For K51.80, 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

K51.80 is the ICD-10-CM diagnosis code for other ulcerative colitis without complications. A form of ulcerative colitis affecting areas of the colon other than the left side, without any complications. K51.80 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, K51.80 maps to Ulcerative Colitis (HCC 81) with a source-labeled community, non-dual, aged reference coefficient of 0.244. No V24 mapping is shown for K51.80; use the applicable model and payment year when reviewing the V28 mapping. 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.

Confirm that the colitis is not limited to the left side, rectum, or proctosigmoid region. For K51.80, 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 K51.80 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Confirm that the colitis is not limited to the left side, rectum, or proctosigmoid region
•Verify no complications are present; if complications exist, use a more specific code from K51.81x series

Clinical Significance

Other ulcerative colitis without complications captures forms of ulcerative colitis that do not fit the standard anatomic classifications of pancolitis, proctitis, rectosigmoiditis, left-sided colitis, or inflammatory polyps. This may include atypical distributions or presentations that still meet the diagnostic criteria for ulcerative colitis.

Documentation Requirements

✓Confirmed ulcerative colitis diagnosis via colonoscopy and biopsy
✓Documentation of the specific extent or type of colitis that does not fit standard subcategories
✓Statement confirming no complications are present
✓Current treatment plan and disease management approach
✓Colonoscopy surveillance schedule

Commonly Confused Codes

•K51.80 vs K51.00/K51.20/K51.30/K51.50: Use anatomically specific codes when extent is clearly documented
•K51.80 vs K51.90: K51.90 is ulcerative colitis unspecified; K51.80 is for identified 'other' types
•K51.80 vs K52.9: K52.9 is noninfective colitis unspecified; K51.80 is specifically ulcerative colitis