What is ICD-10 code I82.522?

I82.522 is the ICD-10-CM diagnosis code for Chronic embolism and thrombosis of left iliac vein. A long-standing blood clot in the iliac vein of the left leg. It belongs to the ICD-10-CM chapter for diseases of the circulatory system (i00-i99). I82.522 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. I82.522 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. I82.522 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. I82.522 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 I82.522?

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 I82.522, 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 I82.522?

The iliac vein is a major deep vein proximal to the femoral vein; ensure documentation specifically identifies this vessel This code is more specific than unspecified deep vein codes and should be used when the iliac vein is documented Because I82.522 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 I82.522: Chronic embolism

ICD-10-CM Code View

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Code lookupI82.522Effective 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)

I82.522

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

Chronic embolism and thrombosis of left iliac vein

A long-standing blood clot in the iliac vein of the left leg.

Buddy Insight

Chronic iliac vein thrombosis represents a significant proximal deep vein thrombosis involving one of the largest veins draining the lower extremity into the inferior vena cava.

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

I82.52Chronic embolism and thrombosis of iliac vein

I82.522Chronic embolism and thrombosis of left iliac vein

Inclusion Terms

Official

Chronic embolism and thrombosis of common iliac vein
Chronic embolism and thrombosis of external iliac vein
Chronic embolism and thrombosis of internal iliac vein

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for I82.522 in this effective period.

Related Child Codes

Official

I82.521Chronic embolism and thrombosis of right iliac vein

I82.523Chronic embolism and thrombosis of iliac vein, bilateral

I82.529Chronic embolism and thrombosis of unspecified iliac vein

Includes

Official

ICD-10-CM does not list Includes notes for I82.522 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for I82.522 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for I82.522 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for I82.522 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for I82.522 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

Specific vein location documented (e.g., iliac)

Documentation confirming left-sided laterality

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

Specific vein location documented (e.g., iliac)

Documentation confirming left-sided laterality

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'

Assigning unspecified laterality when documentation actually states left side; always check operative notes, imaging, and progress notes for laterality

Coding to an unspecified deep vein when the iliac vein is clearly documented — always review imaging and clinical notes for the specific vein involved

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

I82.422 — Acute embolism and thrombosis of iliac vein; ensure chronicity is clearly documented

I82.51- — Chronic embolism and thrombosis of femoral vein; the femoral vein is more distal than the iliac; verify exact vein

I82.50- — Chronic embolism and thrombosis of unspecified deep veins; use the iliac-specific code when documentation names the iliac vein

I82.89- — Chronic embolism and thrombosis of other specified veins; do not use for iliac vein when a specific code exists

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 I82.522 an HCC code?

Yes. I82.522 (Chronic embolism and thrombosis of left iliac vein) 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: I82.522 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: I82.522
Description: Chronic embolism and thrombosis of left iliac vein
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 I82.522 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for I82.522

For I82.522 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 I82.522 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

I82.522 is the ICD-10-CM diagnosis code for chronic embolism and thrombosis of left iliac vein. A long-standing blood clot in the iliac vein of the left leg. I82.522 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, I82.522 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, I82.522 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 iliac vein is a major deep vein proximal to the femoral vein; ensure documentation specifically identifies this vessel. Because I82.522 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 I82.522 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•The iliac vein is a major deep vein proximal to the femoral vein; ensure documentation specifically identifies this vessel
•This code is more specific than unspecified deep vein codes and should be used when the iliac vein is documented

Clinical Significance

Chronic iliac vein thrombosis represents a significant proximal deep vein thrombosis involving one of the largest veins draining the lower extremity into the inferior vena cava. Iliac vein involvement carries a higher risk of post-thrombotic syndrome, chronic venous insufficiency, and recurrent thromboembolism compared to more distal locations. This diagnosis captures substantial vascular disease burden and typically requires long-term anticoagulation and possible interventional management.

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
✓Specific vein location documented (e.g., iliac)
✓Documentation confirming left-sided laterality
✓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

•I82.422: Acute embolism and thrombosis of iliac vein; ensure chronicity is clearly documented
•I82.51-: Chronic embolism and thrombosis of femoral vein; the femoral vein is more distal than the iliac; verify exact vein
•I82.50-: Chronic embolism and thrombosis of unspecified deep veins; use the iliac-specific code when documentation names the iliac vein
•I82.89-: Chronic embolism and thrombosis of other specified veins; do not use for iliac vein when a specific code exists