What is ICD-10 code I82.5Z9?

I82.5Z9 is the ICD-10-CM diagnosis code for Chronic embolism and thrombosis of unspecified deep veins of unspecified distal lower extremity. A chronic blood clot in the deep veins of the lower leg or calf area, but the specific side is not documented. I82.5Z9 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. I82.5Z9 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. I82.5Z9 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. I82.5Z9 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 I82.5Z9?

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 I82.5Z9, V28 maps to Deep Vein Thrombosis and Pulmonary Embolism at RAF 0.294 while V24 mapped to Vascular Disease at RAF 0.288. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting I82.5Z9?

The '9' suffix indicates unspecified laterality; use only when documentation does not specify right, left, or bilateral Query the provider if possible to obtain specific laterality for more precise coding Because I82.5Z9 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 I82.5Z9: Chronic embolism

ICD-10-CM Code View

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Code lookupI82.5Z9Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the circulatory system (I00-I99) / Diseases of veins, lymphatic vessels and lymph nodes, not elsewhere classified (I80-I89)

I82.5Z9

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

Chronic embolism and thrombosis of unspecified deep veins of unspecified distal lower extremity

A chronic blood clot in the deep veins of the lower leg or calf area, but the specific side is not documented.

Buddy Insight

CMS-HCC V28

Mapped

HCC 267

Deep Vein Thrombosis and Pulm...

RAF 0.294

CMS-HCC V24

Mapped

HCC 108

Vascular Disease

RAF 0.288

ACA/HHS

Mapped

HCC 156

HHS-HCC 156

Varies by metal level

ESRD/PACE

Mapped

HCC 108

Vascular Disease

RAF 0.073

RXHCC

Mapped

HCC 215

Pulmonary Embolism and Other ...

RAF 0.228

Code Book Path

Official

I82.5Chronic embolism and thrombosis of deep veins of lower extremity

I82.5ZChronic embolism and thrombosis of unspecified deep veins of distal lower extremity

I82.5Z9Chronic embolism and thrombosis of unspecified deep veins of unspecified distal lower extremity

Inclusion Terms

Official

Chronic embolism and thrombosis of deep veins of calf NOS
Chronic embolism and thrombosis of deep veins of lower leg NOS

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for I82.5Z9 in this effective period.

Related Child Codes

Official

I82.5Z1Chronic embolism and thrombosis of unspecified deep veins of right distal lower extremity

I82.5Z2Chronic embolism and thrombosis of unspecified deep veins of left distal lower extremity

I82.5Z3Chronic embolism and thrombosis of unspecified deep veins of distal lower extremity, bilateral

Includes

Official

ICD-10-CM does not list Includes notes for I82.5Z9 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for I82.5Z9 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for I82.5Z9 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for I82.5Z9 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for I82.5Z9 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Provider documentation explicitly stating 'chronic' deep vein thrombosis (not assumed from duration of treatment)

Clinical evidence supporting the diagnosis such as duplex ultrasound, venography, or other imaging results

Query provider for specific vein location when possible

Query provider for laterality (right, left, or bilateral) when not documented

MEAT Support

HCC Buddy guidance

Provider documentation explicitly stating 'chronic' deep vein thrombosis (not assumed from duration of treatment)

Clinical evidence supporting the diagnosis such as duplex ultrasound, venography, or other imaging results

Query provider for specific vein location when possible

Query provider for laterality (right, left, or bilateral) when not documented

Audit Caution

HCC Buddy guidance

Confusing acute and chronic deep vein thrombosis — these have different code families (I82.4- for acute lower extremity, I82.5- for chronic lower extremity) and the provider must explicitly document 'chronic'

Defaulting to 'unspecified' laterality without querying the provider; always review imaging reports and clinical notes for laterality before accepting an unspecified code

Using an unspecified deep vein code when the specific vein (femoral, iliac, popliteal, tibial, peroneal, or calf muscular) is documented elsewhere in the chart — always code to the highest level of specificity

Assuming deep vein thrombosis is chronic solely because the patient has been on anticoagulation for a long time; the provider must explicitly document the condition as chronic

Common Mistakes

HCC Buddy guidance

I82.5Z- includes tibial, peroneal, and calf muscular veins collectively; if a specific vein is documented, use I82.54-, I82.55-, or I82.56- instead

I82.5Y- — Chronic embolism of unspecified deep veins of proximal lower extremity; distal refers to below the knee, proximal refers to above the knee

I82.50- — Chronic embolism of unspecified deep veins of lower extremity (neither proximal nor distal specified)

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 I82.5Z9 an HCC code?

Yes. I82.5Z9 (Chronic embolism and thrombosis of unspecified deep veins of unspecified distal lower extremity) maps to Deep Vein Thrombosis and Pulmonary Embolism under the CMS-HCC V28 risk adjustment model (and Vascular Disease under V24), with a community non-dual aged RAF of 0.294. It is billable for payment year 2026.

Coder answer: I82.5Z9 is billable and maps to V28 HCC 267, Deep Vein Thrombosis and Pulmonary Embolism. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: I82.5Z9
Description: Chronic embolism and thrombosis of unspecified deep veins of unspecified distal lower extremity
HCC (V28): HCC 267 — Deep Vein Thrombosis and Pulmonary Embolism
RAF: 0.294
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 267, Deep Vein Thrombosis and Pulmonary Embolism

0.294

V24HCC 108, Vascular Disease

0.288

ESRDHCC 108, Vascular Disease

0.073

RxHCCHCC 215, Pulmonary Embolism and Other Vascular Disease

0.228

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 I82.5Z9 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for I82.5Z9

For I82.5Z9 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 I82.5Z9 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

I82.5Z9 is the ICD-10-CM diagnosis code for chronic embolism and thrombosis of unspecified deep veins of unspecified distal lower extremity. A chronic blood clot in the deep veins of the lower leg or calf area, but the specific side is not documented. I82.5Z9 sits in the ICD-10-CM chapter for diseases of the circulatory system (i00-i99), within the section covering diseases of veins, lymphatic vessels and lymph nodes, not elsewhere classified (i80-i89).

Under the CMS-HCC V28 risk adjustment model, I82.5Z9 maps to Deep Vein Thrombosis and Pulmonary Embolism (HCC 267) with a community, non-dual, aged base RAF weight of 0.294. Under the older CMS-HCC V24 model, I82.5Z9 maps to Vascular Disease (HCC 108) with a community, non-dual, aged base RAF weight of 0.288. 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.

The '9' suffix indicates unspecified laterality; use only when documentation does not specify right, left, or bilateral. Because I82.5Z9 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 I82.5Z9 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•The '9' suffix indicates unspecified laterality; use only when documentation does not specify right, left, or bilateral
•Query the provider if possible to obtain specific laterality for more precise coding

Clinical Significance

Chronic deep vein thrombosis of the distal lower extremity (unspecified) indicates a long-standing thrombus that has organized within the venous system, often leading to post-thrombotic syndrome with chronic swelling, pain, and skin changes. This condition requires ongoing anticoagulation management and monitoring for recurrent thromboembolism and venous insufficiency. Accurate capture of chronic deep vein thrombosis is essential for risk adjustment as it reflects persistent vascular disease burden.

Documentation Requirements

✓Provider documentation explicitly stating 'chronic' deep vein thrombosis (not assumed from duration of treatment)
✓Clinical evidence supporting the diagnosis such as duplex ultrasound, venography, or other imaging results
✓Query provider for specific vein location when possible
✓Query provider for laterality (right, left, or bilateral) when not documented
✓Current treatment plan including anticoagulation therapy and duration
✓Assessment and monitoring notes demonstrating the condition is being actively managed
✓Documentation of chronicity such as 'chronic,' 'old,' 'long-standing,' or history of prior acute deep vein thrombosis that has transitioned to chronic status

Commonly Confused Codes

•I82.5Z- includes tibial, peroneal, and calf muscular veins collectively; if a specific vein is documented, use I82.54-, I82.55-, or I82.56- instead
•I82.5Y-: Chronic embolism of unspecified deep veins of proximal lower extremity; distal refers to below the knee, proximal refers to above the knee
•I82.50-: Chronic embolism of unspecified deep veins of lower extremity (neither proximal nor distal specified)