What is ICD-10 code K51.413?

K51.413 is the ICD-10-CM diagnosis code for Inflammatory polyps of colon with fistula. Growths in the colon caused by inflammation that have created an abnormal tunnel or connection between the colon and another organ or the skin. K51.413 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. K51.413 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. K51.413 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. K51.413 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 K51.413 map to under V28?

K51.413 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.

What documentation supports K51.413?

Document the location and type of fistula (enterocutaneous, enterovesical, etc.) in the medical record for clinical clarity Fistulas are serious complications that typically require additional intervention; ensure the fistula is documented by the provider Because K51.413 maps to an HCC category, the documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) before the diagnosis is used for risk adjustment. See the MEAT criteria checklist at /meat-criteria for what Monitor, Evaluate, Assess, or Treat looks like in a note. MEAT is generic documentation evidence, not a payer-specific rule.

2026 ICD-10-CM K51.413: Inflammatory polyps

K51.413 maps to CMS-HCC V28 81. A source-labeled RAF reference is available. Documentation must support MEAT. MEAT criteria · RAF Calculator · HCC Buddy coding tools

ICD-10-CM Code View

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Code lookupK51.413Effective periodFY2026 Apr Update (Apr 1-Sep 30)

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

K51.413

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

Inflammatory polyps of colon with fistula

Growths in the colon caused by inflammation that have created an abnormal tunnel or connection between the colon and another organ or the skin.

Buddy Insight

Inflammatory polyps of the colon with fistula represents the combination of pseudopolyps from prior inflammatory damage and an abnormal fistulous connection.

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

K51.4Inflammatory polyps of colon

K51.41Inflammatory polyps of colon with complications

K51.413Inflammatory polyps of colon with fistula

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for K51.413 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for K51.413 in this effective period.

Related Child Codes

Official

K51.411Inflammatory polyps of colon with rectal bleeding

K51.412Inflammatory polyps of colon with intestinal obstruction

K51.414Inflammatory polyps of colon with abscess

K51.418Inflammatory polyps of colon with other complication

K51.419Inflammatory polyps of colon with unspecified complications

Includes

Official

ICD-10-CM does not list Includes notes for K51.413 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for K51.413 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for K51.413 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for K51.413 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for K51.413 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Colonoscopy documenting inflammatory polyps

Documentation of fistula type and location

Imaging confirmation of fistula tract

Biopsy confirming inflammatory nature of polyps

MEAT Support

HCC Buddy guidance

Colonoscopy documenting inflammatory polyps

Documentation of fistula type and location

Imaging confirmation of fistula tract

Biopsy confirming inflammatory nature of polyps

Audit Caution

HCC Buddy guidance

Not reconsidering Crohn disease diagnosis when fistula is present in ulcerative colitis

Using separate codes for polyps and fistula instead of the combination code

Failing to document fistula location and type

Using K51.418 (other complication) when fistula has its own code

Common Mistakes

HCC Buddy guidance

K51.413 vs K50.113 — K50.113 is Crohn disease with fistula; reconsider diagnosis when fistula is present

K51.413 vs K60.3 — K60.3 is anal fistula not related to inflammatory bowel disease

K51.413 vs K51.411 — K51.411 is inflammatory polyps with rectal bleeding, a different complication

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 K51.413 an HCC code?

Yes. K51.413 (Inflammatory polyps of colon with fistula) 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: K51.413 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: K51.413
Description: Inflammatory polyps of colon with fistula
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 K51.413 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT Criteria for K51.413

For K51.413 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 K51.413 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

K51.413 is the ICD-10-CM diagnosis code for inflammatory polyps of colon with fistula. Growths in the colon caused by inflammation that have created an abnormal tunnel or connection between the colon and another organ or the skin. K51.413 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, K51.413 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 K51.413; use the applicable model and payment year when reviewing the V28 mapping. 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. 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.

Document the location and type of fistula (enterocutaneous, enterovesical, etc.) in the medical record for clinical clarity. Because K51.413 maps to an HCC category, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) before the diagnosis is used for risk adjustment. 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 K51.413 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Document the location and type of fistula (enterocutaneous, enterovesical, etc.) in the medical record for clinical clarity
•Fistulas are serious complications that typically require additional intervention; ensure the fistula is documented by the provider

Clinical Significance

Inflammatory polyps of the colon with fistula represents the combination of pseudopolyps from prior inflammatory damage and an abnormal fistulous connection. This dual complication indicates severe underlying disease and typically requires surgical management. The presence of fistula should prompt consideration of whether the diagnosis is truly ulcerative colitis or Crohn disease.

Documentation Requirements

✓Colonoscopy documenting inflammatory polyps
✓Documentation of fistula type and location
✓Imaging confirmation of fistula tract
✓Biopsy confirming inflammatory nature of polyps
✓Provider statement linking both complications to the underlying colitis
✓Surgical consultation documentation

Commonly Confused Codes

•K51.413 vs K50.113: K50.113 is Crohn disease with fistula; reconsider diagnosis when fistula is present
•K51.413 vs K60.3: K60.3 is anal fistula not related to inflammatory bowel disease
•K51.413 vs K51.411: K51.411 is inflammatory polyps with rectal bleeding, a different complication