What is ICD-10 code I70.331?

I70.331 is the ICD-10-CM diagnosis code for Atherosclerosis of unspecified type of bypass graft(s) of the right leg with ulceration of thigh. Hardening and narrowing of a bypass graft in the right leg with an open sore on the thigh. I70.331 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. I70.331 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. I70.331 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. I70.331 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 I70.331?

I70.331 does not map to a payment HCC under either the CMS-HCC V28 risk adjustment model or the older V24 model. V28 reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition. Because neither model rewards I70.331 with a risk adjustment factor, it contributes zero to a Medicare Advantage beneficiary's RAF score in either version. Coders should check whether provider documentation supports a more specific child code that does map to a payment HCC.

What should coders know when reporting I70.331?

Verify the ulcer location is specifically the thigh and not another part of the leg Document the stage and severity of the ulcer if available for additional coding

I70.331 ICD-10 Code: Atherosclerosis

ICD-10-CM Code View

HCC Buddy Code Card

Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.

Code lookupI70.331Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the circulatory system (I00-I99) / Diseases of arteries, arterioles and capillaries (I70-I79)

I70.331

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

Atherosclerosis of unspecified type of bypass graft(s) of the right leg with ulceration of thigh

Hardening and narrowing of a bypass graft in the right leg with an open sore on the thigh.

Buddy Insight

Atherosclerosis of bypass graft(s) with ulceration indicates severe peripheral arterial disease (Fontaine Stage IV/Rutherford Category 5) where impaired blood flow has caused tissue breakdown.

CMS-HCC V28

Not risk-adjusted for this model/period.

RAF 0

CMS-HCC V24

Not risk-adjusted for this model/period.

RAF 0

ACA/HHS

Not risk-adjusted for this model/period.

RAF 0

ESRD/PACE

Not risk-adjusted for this model/period.

RAF 0

RXHCC

Mapped

HCC 311

Diabetic and Chronic Skin Ulcer

RAF 0.0

Code Trumping

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Compare selected patient codes to show trumped or trumps impact.

Code Book Path

Official

I70.3Atherosclerosis of unspecified type of bypass graft(s) of the extremities

I70.33Atherosclerosis of unspecified type of bypass graft(s) of the right leg with ulceration

I70.331Atherosclerosis of unspecified type of bypass graft(s) of the right leg with ulceration of thigh

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for I70.331 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for I70.331 in this effective period.

Related Child Codes

Official

I70.332Atherosclerosis of unspecified type of bypass graft(s) of the right leg with ulceration of calf

I70.333Atherosclerosis of unspecified type of bypass graft(s) of the right leg with ulceration of ankle

I70.334Atherosclerosis of unspecified type of bypass graft(s) of the right leg with ulceration of heel and midfoot

I70.335Atherosclerosis of unspecified type of bypass graft(s) of the right leg with ulceration of other part of foot

I70.338Atherosclerosis of unspecified type of bypass graft(s) of the right leg with ulceration of other part of lower leg

Includes

Official

any condition classifiable to I70.311 and I70.321
chronic limb-threatening ischemia of unspecified type of bypass graft(s) of the right leg with ulceration
critical limb ischemia of unspecified type of bypass graft(s) of the right leg with ulceration

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for I70.331 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for I70.331 in this effective period.

Use Additional

Official

code to identify severity of ulcer (L97.-)

Code Also

Official

ICD-10-CM does not list Code Also instructions for I70.331 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Clinical diagnosis of peripheral atherosclerosis explicitly documented by the provider

Specification of the affected vessel type (bypass graft(s))

Laterality clearly documented (right leg)

Documentation of the ulcer location (thigh) with description of size, depth, and wound characteristics

MEAT Support

HCC Buddy guidance

Clinical diagnosis of peripheral atherosclerosis explicitly documented by the provider

Specification of the affected vessel type (bypass graft(s))

Laterality clearly documented (right leg)

Documentation of the ulcer location (thigh) with description of size, depth, and wound characteristics

Audit Caution

HCC Buddy guidance

Using native artery codes (I70.2xx) when the patient has a documented bypass graft — always verify surgical history and code to the appropriate graft category

Defaulting to unspecified graft type when the medical record documents the specific graft type (autologous vein, nonnautologous biological, or nonbiological) — query the record for graft details before coding to unspecified

Failing to document the specific ulcer site (thigh) — the code requires specificity of the anatomic location of the ulcer

Coding a venous stasis ulcer or diabetic neuropathic ulcer as an atherosclerotic arterial ulcer — the etiology must be confirmed as arterial insufficiency from atherosclerosis

Common Mistakes

HCC Buddy guidance

I70.2xx (native artery series) — Use I70.2xx when atherosclerosis involves the native arteries rather than a bypass graft; do not use bypass graft codes without documentation of prior graft surgery

I70.321-I70.329 (bypass graft with rest pain) — Use rest pain codes only when there is no ulceration; ulceration represents a more advanced manifestation

L97.x (Non-pressure chronic ulcer of lower limb) — L97 codes are for ulcers without specified atherosclerotic etiology; an additional L97 code may be used to identify ulcer severity

I70.361-I70.369 (bypass graft with gangrene) — Gangrene codes take precedence when tissue necrosis is present alongside ulceration

Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.

Is I70.331 an HCC code?

No. I70.331 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.

HCC Category Mapping

RxHCCHCC 311, Diabetic and Chronic Skin Ulcer

0.000

RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. 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.

MEAT Criteria for I70.331

For I70.331to 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 I70.331 during that encounter, not just copy-forwarded from a problem list.

What This Code Means

I70.331 is the ICD-10-CM diagnosis code for atherosclerosis of unspecified type of bypass graft(s) of the right leg with ulceration of thigh. Hardening and narrowing of a bypass graft in the right leg with an open sore on the thigh. I70.331 sits in the ICD-10-CM chapter for diseases of the circulatory system (i00-i99), within the section covering diseases of arteries, arterioles and capillaries (i70-i79).

I70.331 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.

This code does not map to an HCC under the CMS-HCC V28 model. It does not map to an HCC under the CMS-HCC V24 model. It does not map to an HCC under the ESRD model. In the RxHCC model, it maps to RxHCC 311 but carries a RAF weight of 0.0, meaning it is recognized for prescription drug risk adjustment but does not independently increase the RAF score. While these ulceration codes do not map to CMS-HCC V24 or V28 directly, they are recognized in the RxHCC model. The ulceration indicates significant disease severity that should be captured for complete clinical documentation even when HCC impact is limited.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for I70.331 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Verify the ulcer location is specifically the thigh and not another part of the leg
•Document the stage and severity of the ulcer if available for additional coding

Clinical Significance

Atherosclerosis of bypass graft(s) with ulceration indicates severe peripheral arterial disease (Fontaine Stage IV/Rutherford Category 5) where impaired blood flow has caused tissue breakdown. These arterial ulcers require specialized wound care, vascular assessment, and often revascularization to promote healing and prevent amputation. This combination code captures both the underlying vascular disease and the ulcerative complication, reflecting the increased care complexity and resource needs.

Documentation Requirements

✓Clinical diagnosis of peripheral atherosclerosis explicitly documented by the provider
✓Specification of the affected vessel type (bypass graft(s))
✓Laterality clearly documented (right leg)
✓Documentation of the ulcer location (thigh) with description of size, depth, and wound characteristics
✓Confirmation that the ulcer is arterial in etiology (as opposed to venous, diabetic neuropathic, or pressure ulcer)
✓Wound assessment details including wound bed description, drainage, presence of infection, and staging if applicable
✓Vascular assessment findings (ankle-brachial index, pulse examination, or arterial Doppler studies) supporting ischemic etiology
✓Current wound care and vascular treatment plan
✓Documentation of prior bypass graft surgery with type of graft if known (autologous vein, nonnautologous biological, or nonbiological — code to specific graft type when documented)

Commonly Confused Codes

•I70.2xx (native artery series): Use I70.2xx when atherosclerosis involves the native arteries rather than a bypass graft; do not use bypass graft codes without documentation of prior graft surgery
•I70.321-I70.329 (bypass graft with rest pain): Use rest pain codes only when there is no ulceration; ulceration represents a more advanced manifestation
•L97.x (Non-pressure chronic ulcer of lower limb): L97 codes are for ulcers without specified atherosclerotic etiology; an additional L97 code may be used to identify ulcer severity
•I70.361-I70.369 (bypass graft with gangrene): Gangrene codes take precedence when tissue necrosis is present alongside ulceration
•I70.431-I70.45, I70.531-I70.55, I70.631-I70.65 (specific graft type with ulceration): Code to the specific graft type when documented