What is ICD-10 code K26.1?

K26.1 is the ICD-10-CM diagnosis code for Acute duodenal ulcer with perforation. A newly developed ulcer in the duodenum that has broken through the duodenal wall, creating a hole that allows digestive contents to leak into the abdominal cavity. K26.1 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. K26.1 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. K26.1 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. K26.1 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.

What is the V28 vs V24 difference for K26.1?

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 K26.1, 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 should coders know when reporting K26.1?

Perforation is a surgical emergency; ensure documentation clearly indicates perforation and acute status Distinguish from K26.2 which includes both hemorrhage and perforation Because K26.1 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.

2026 ICD-10-CM K26.1: Acute duodenal ulcer

ICD-10-CM Code View

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Code lookupK26.1Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the digestive system (K00-K95) / Diseases of esophagus, stomach and duodenum (K20-K31)

K26.1

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

Acute duodenal ulcer with perforation

A newly developed ulcer in the duodenum that has broken through the duodenal wall, creating a hole that allows digestive contents to leak into the abdominal cavity.

Buddy Insight

Acute duodenal ulcer with perforation is a surgical emergency where the duodenal wall is breached, allowing intestinal contents to spill into the peritoneal cavity.

CMS-HCC V28

Mapped

HCC 78

Intestinal Obstruction/Perfor...

RAF 0.326

CMS-HCC V24

Mapped

HCC 33

Intestinal Obstruction/Perfor...

RAF 0.219

ACA/HHS

Mapped

HCC 42

HHS-HCC 42

Varies by metal level

ESRD/PACE

Mapped

HCC 33

Intestinal Obstruction/Perfor...

RAF 0.078

RXHCC

N/A

—

Not risk-adjusted for this model/period.

Not mapped

Code Book Path

Official

K26Duodenal ulcer

K26.1Acute duodenal ulcer with perforation

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for K26.1 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for K26.1 in this effective period.

Related Child Codes

Official

K26.0Acute duodenal ulcer with hemorrhage

K26.2Acute duodenal ulcer with both hemorrhage and perforation

K26.3Acute duodenal ulcer without hemorrhage or perforation

K26.4Chronic or unspecified duodenal ulcer with hemorrhage

K26.5Chronic or unspecified duodenal ulcer with perforation

Includes

Official

erosion (acute) of duodenum
duodenum ulcer (peptic)
postpyloric ulcer (peptic)

Excludes 1

Official

peptic ulcer NOS (K27.-)

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for K26.1 in this effective period.

Use Additional

Official

code to identify:
alcohol abuse and dependence (F10.-)

Code Also

Official

ICD-10-CM does not list Code Also instructions for K26.1 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Provider documentation of acute duodenal ulcer with confirmed perforation

Evidence of perforation (free air under diaphragm on X-ray, CT findings, or operative report)

Acuity specified as acute

Location confirmed as duodenal (first part of small intestine), not gastric

MEAT Support

HCC Buddy guidance

Provider documentation of acute duodenal ulcer with confirmed perforation

Evidence of perforation (free air under diaphragm on X-ray, CT findings, or operative report)

Acuity specified as acute

Location confirmed as duodenal (first part of small intestine), not gastric

Audit Caution

HCC Buddy guidance

Confusing gastric (K25) with duodenal (K26) location — anatomic site specificity is critical

Using the site-unspecified code (K27) when the duodenal location is documented

Failing to capture hemorrhage if it is also present (would require K26.2)

Not verifying acute vs. chronic status, which changes the fourth character of the code

Common Mistakes

HCC Buddy guidance

K26.0 — Acute duodenal ulcer with hemorrhage: bleeding only, no perforation

K26.2 — Acute duodenal ulcer with both hemorrhage and perforation: use when both complications exist

K26.5 — Chronic or unspecified duodenal ulcer with perforation: different acuity

K25.1 — Acute gastric ulcer with perforation: different anatomic location (stomach vs. duodenum)

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 K26.1 an HCC code?

Yes. K26.1 (Acute duodenal ulcer with perforation) 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: K26.1 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: K26.1
Description: Acute duodenal ulcer with perforation
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

V24HCC 33, Intestinal Obstruction/Perforation

0.219

ESRDHCC 33, Intestinal Obstruction/Perforation

0.078

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 K26.1 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for K26.1

For K26.1 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 K26.1 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

K26.1 is the ICD-10-CM diagnosis code for acute duodenal ulcer with perforation. A newly developed ulcer in the duodenum that has broken through the duodenal wall, creating a hole that allows digestive contents to leak into the abdominal cavity. K26.1 sits in the ICD-10-CM chapter for diseases of the digestive system (k00-k95), within the section covering diseases of esophagus, stomach and duodenum (k20-k31).

Under the CMS-HCC V28 risk adjustment model, K26.1 maps to Intestinal Obstruction/Perforation (HCC 78) with a community, non-dual, aged base RAF weight of 0.326. Under the older V24 model, K26.1 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.

Perforation is a surgical emergency; ensure documentation clearly indicates perforation and acute status. Because K26.1 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 K26.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Perforation is a surgical emergency; ensure documentation clearly indicates perforation and acute status
•Distinguish from K26.2 which includes both hemorrhage and perforation

Clinical Significance

Acute duodenal ulcer with perforation is a surgical emergency where the duodenal wall is breached, allowing intestinal contents to spill into the peritoneal cavity. Duodenal perforations are more common than gastric perforations and are strongly associated with Helicobacter pylori infection and NSAID use. This condition requires immediate surgical intervention and reflects high-acuity care needs.

Documentation Requirements

✓Provider documentation of acute duodenal ulcer with confirmed perforation
✓Evidence of perforation (free air under diaphragm on X-ray, CT findings, or operative report)
✓Acuity specified as acute
✓Location confirmed as duodenal (first part of small intestine), not gastric
✓Surgical findings and intervention details
✓Helicobacter pylori and NSAID use assessment

Commonly Confused Codes

•K26.0: Acute duodenal ulcer with hemorrhage: bleeding only, no perforation
•K26.2: Acute duodenal ulcer with both hemorrhage and perforation: use when both complications exist
•K26.5: Chronic or unspecified duodenal ulcer with perforation: different acuity
•K25.1: Acute gastric ulcer with perforation: different anatomic location (stomach vs. duodenum)
•K27.1: Acute peptic ulcer, site unspecified, with perforation: use only when the site truly cannot be determined