What is ICD-10 code K51.912?

K51.912 is the ICD-10-CM diagnosis code for Ulcerative colitis, unspecified with intestinal obstruction. Ulcerative colitis of unspecified extent with a blockage in the intestines. It belongs to the ICD-10-CM chapter for diseases of the digestive system (k00-k95). K51.912 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. K51.912 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. K51.912 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. K51.912 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 K51.912 map to under V28?

K51.912 maps to CMS-HCC V28 78 (Intestinal Obstruction/Perforation). The category number and label come from the CMS-HCC V28 model file for payment year 2026.

What does K51.912 pay in RAF?

K51.912 carries a community, non-dual, aged (CNA) RAF weight of 0.326 under CMS-HCC V28 for payment year 2026. The weight comes from the CMS V28 relative-factor file, not a hand-typed table.

What is the V28 vs V24 difference for K51.912?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. For K51.912, V28 maps to Intestinal Obstruction/Perforation at RAF 0.326 while V24 mapped to Intestinal Obstruction/Perforation at RAF 0.219. Both models can still appear in legacy data and in payer-specific lookback periods.

What documentation supports K51.912?

Verify whether the obstruction is partial or complete, as this affects clinical severity and treatment decisions. Distinguish between obstruction caused by active inflammation versus stricture formation, as this may require additional coding. Because K51.912 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score. 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 K51.912: Ulcerative colitis

K51.912 maps to CMS-HCC V28 78 (RAF 0.326). Documentation must support MEAT. MEAT criteria · RAF calculator · HCC coding software

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Code lookupK51.912Effective periodFY2026 Apr Update (Apr 1-Sep 30)

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

K51.912

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

Ulcerative colitis, unspecified with intestinal obstruction

Ulcerative colitis of unspecified extent with a blockage in the intestines.

Buddy Insight

Ulcerative colitis, unspecified, with intestinal obstruction indicates bowel blockage complicating ulcerative colitis of undetermined extent.

CMS-HCC V28

Mapped

HCC 78

Intestinal Obstruction/Perfor...

RAF 0.326

+ HCC 81

CMS-HCC V24

Mapped

HCC 33

Intestinal Obstruction/Perfor...

RAF 0.219

+ HCC 35

ACA/HHS

Mapped

HCC 45, 48

HHS-HCC 45, 48

Varies by metal level

ESRD/PACE

Mapped

HCC 33

Intestinal Obstruction/Perfor...

RAF 0.078

+ HCC 35

RXHCC

Mapped

HCC 67

Inflammatory Bowel Disease

RAF 0.494

Code Book Path

Official

K51.9Ulcerative colitis, unspecified

K51.91Ulcerative colitis, unspecified, with complications

K51.912Ulcerative colitis, unspecified with intestinal obstruction

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for K51.912 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for K51.912 in this effective period.

Related Child Codes

Official

K51.911Ulcerative colitis, unspecified with rectal bleeding

K51.913Ulcerative colitis, unspecified with fistula

K51.914Ulcerative colitis, unspecified with abscess

K51.918Ulcerative colitis, unspecified with other complication

K51.919Ulcerative colitis, unspecified with unspecified complications

Includes

Official

ICD-10-CM does not list Includes notes for K51.912 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for K51.912 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for K51.912 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for K51.912 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for K51.912 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Confirmed ulcerative colitis diagnosis

Imaging evidence of intestinal obstruction

Documentation of obstruction type (partial vs. complete) and location

Provider statement linking obstruction to the colitis

MEAT Support

HCC Buddy guidance

Confirmed ulcerative colitis diagnosis

Imaging evidence of intestinal obstruction

Documentation of obstruction type (partial vs. complete) and location

Provider statement linking obstruction to the colitis

Audit Caution

HCC Buddy guidance

Not using the imaging for obstruction to also determine disease extent for more specific coding

Coding the obstruction separately instead of using the combination code

Failing to evaluate for toxic megacolon when obstruction occurs in active colitis

Using unspecified extent when imaging clearly shows disease distribution

Common Mistakes

HCC Buddy guidance

K51.912 vs K56.69 — K56.69 is other intestinal obstruction unrelated to inflammatory bowel disease

K51.912 vs K51.012/K51.312/K51.512 — Use extent-specific codes when the anatomic extent is known

K51.912 vs K51.90 — K51.90 is without complications

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 K51.912 an HCC code?

Yes. K51.912 (Ulcerative colitis, unspecified with intestinal obstruction) maps to Intestinal Obstruction/Perforation under the CMS-HCC V28 risk adjustment model (and Intestinal Obstruction/Perforation under V24), with a community non-dual aged RAF of 0.326. It is billable for payment year 2026.

Coder answer: K51.912 is billable and maps to V28 HCC 78, Intestinal Obstruction/Perforation. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: K51.912
Description: Ulcerative colitis, unspecified with intestinal obstruction
HCC (V28): HCC 78 — Intestinal Obstruction/Perforation
RAF: 0.326
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 78, Intestinal Obstruction/Perforation

0.326

+ HCC 81, Ulcerative Colitis0.244

V24HCC 33, Intestinal Obstruction/Perforation

0.219

+ HCC 35, Inflammatory Bowel Disease0.308

ESRDHCC 33, Intestinal Obstruction/Perforation

0.078

+ HCC 35, Inflammatory Bowel Disease0.048

RxHCCHCC 67, Inflammatory Bowel Disease

0.494

Each model's RAF is its CMS base weight for that model's standard population, so 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 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.

Work K51.912 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for K51.912

For K51.912 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 K51.912 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

K51.912 is the ICD-10-CM diagnosis code for ulcerative colitis, unspecified with intestinal obstruction. Ulcerative colitis of unspecified extent with a blockage in the intestines. K51.912 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, K51.912 maps to Intestinal Obstruction/Perforation (HCC 78) with a community, non-dual, aged base RAF weight of 0.326. Under the older V24 model, K51.912 mapped to the same category but with a base RAF weight of 0.219, V28 recalibrated weights across the entire model. 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.

Verify whether the obstruction is partial or complete, as this affects clinical severity and treatment decisions. Because K51.912 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 K51.912 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Verify whether the obstruction is partial or complete, as this affects clinical severity and treatment decisions.
•Distinguish between obstruction caused by active inflammation versus stricture formation, as this may require additional coding.

Clinical Significance

Ulcerative colitis, unspecified, with intestinal obstruction indicates bowel blockage complicating ulcerative colitis of undetermined extent. Intestinal obstruction is a serious complication requiring urgent evaluation. In this clinical scenario, imaging performed to evaluate the obstruction should also help clarify the disease extent for more specific coding.

Documentation Requirements

✓Confirmed ulcerative colitis diagnosis
✓Imaging evidence of intestinal obstruction
✓Documentation of obstruction type (partial vs. complete) and location
✓Provider statement linking obstruction to the colitis
✓Treatment plan for obstruction management
✓Assessment for toxic megacolon

Commonly Confused Codes

•K51.912 vs K56.69: K56.69 is other intestinal obstruction unrelated to inflammatory bowel disease
•K51.912 vs K51.012/K51.312/K51.512: Use extent-specific codes when the anatomic extent is known
•K51.912 vs K51.90: K51.90 is without complications