What is ICD-10 code I82.C21?

I82.C21 is the ICD-10-CM diagnosis code for Chronic embolism and thrombosis of right internal jugular vein. It belongs to the ICD-10-CM chapter for diseases of the circulatory system (i00-i99). I82.C21 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. I82.C21 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.C21 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.C21 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.C21?

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.C21, V28 maps to Vascular Disease at RAF 0.356 while V24 mapped to Vascular Disease at RAF 0.297. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting I82.C21?

Verify documentation specifies 'chronic' duration and 'right' side to ensure accurate code selection, as laterality is required for this code Investigate the underlying cause (malignancy, trauma, central line placement, hypercoagulable state) as this may require additional diagnosis codes to capture the complete clinical picture Because I82.C21 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.

I82.C21 ICD-10 Code: Chronic embolism

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 lookupI82.C21Effective 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.C21

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

Chronic embolism and thrombosis of right internal jugular vein

A blood clot that has formed in the right internal jugular vein (a major vein in the neck) and has persisted over time. This condition can restrict blood flow from the head and brain back to the heart.

Buddy Insight

CMS-HCC V28

Mapped

HCC 267

Vascular Disease

RAF 0.356

CMS-HCC V24

Mapped

HCC 108

Vascular Disease

RAF 0.297

ACA/HHS

Not risk-adjusted for this model/period.

RAF 0

ESRD/PACE

Mapped

HCC 108

Vascular Disease

RAF 0.0

RXHCC

Mapped

HCC 215

Pulmonary Embolism and Other ...

RAF 0.0

Code Trumping

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Code Book Path

Official

I82.CEmbolism and thrombosis of internal jugular vein

I82.C2Chronic embolism and thrombosis of internal jugular vein

I82.C21Chronic embolism and thrombosis of right internal jugular vein

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for I82.C21 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for I82.C21 in this effective period.

Related Child Codes

Official

I82.C22Chronic embolism and thrombosis of left internal jugular vein

I82.C23Chronic embolism and thrombosis of internal jugular vein, bilateral

I82.C29Chronic embolism and thrombosis of unspecified internal jugular vein

Includes

Official

ICD-10-CM does not list Includes notes for I82.C21 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for I82.C21 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for I82.C21 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for I82.C21 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for I82.C21 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Provider documentation explicitly stating chronic embolism or thrombosis of the internal jugular vein

Laterality must be documented (right side) — do not assume from context

Clinical findings supporting the diagnosis (e.g., swelling, pain, imaging results such as duplex ultrasound or CT venography)

Current treatment plan including anticoagulation therapy type, duration, and monitoring parameters

MEAT Support

HCC Buddy guidance

Provider documentation explicitly stating chronic embolism or thrombosis of the internal jugular vein

Laterality must be documented (right side) — do not assume from context

Clinical findings supporting the diagnosis (e.g., swelling, pain, imaging results such as duplex ultrasound or CT venography)

Current treatment plan including anticoagulation therapy type, duration, and monitoring parameters

Audit Caution

HCC Buddy guidance

Coding chronic when the documentation actually supports acute presentation — always verify the acuity from the clinical note

Confusing the internal jugular vein with adjacent veins (e.g., subclavian) — verify the exact vessel documented

Failing to code the underlying etiology when documented (e.g., malignancy, central venous catheter, thoracic outlet syndrome)

Reporting a resolved thrombosis as chronic when the provider documents it is no longer present — chronic implies the clot is still there

Common Mistakes

HCC Buddy guidance

I82.C11 — Acute (not chronic) embolism and thrombosis of the right internal jugular vein; use for newly formed clots

I82.B21 — Chronic embolism and thrombosis of the right subclavian vein; different vessel near the collarbone

I80.8 — Phlebitis and thrombophlebitis of other sites; inflammatory component distinguishes this from pure thrombosis

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 I82.C21 an HCC code?

Yes. I82.C21 maps to Vascular Disease under the CMS-HCC V28 risk adjustment model (and Vascular Disease under V24).

HCC Category Mapping

V28HCC 267, Vascular Disease

0.356

V24HCC 108, Vascular Disease

0.297

ESRDHCC 108, Vascular Disease

0.000

RxHCCHCC 215, Pulmonary Embolism and Other Vascular Disease

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 I82.C21

For I82.C21to 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.C21 during that encounter, not just copy-forwarded from a problem list.

What This Code Means

I82.C21 is the ICD-10-CM diagnosis code for chronic embolism and thrombosis of right internal jugular vein. A blood clot that has formed in the right internal jugular vein (a major vein in the neck) and has persisted over time. This condition can restrict blood flow from the head and brain back to the heart. I82.C21 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.C21 maps to Vascular Disease (HCC 267) with a community, non-dual, aged base RAF weight of 0.356. Under the older V24 model, I82.C21 mapped to the same category but with a base RAF weight of 0.297, 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 documentation specifies 'chronic' duration and 'right' side to ensure accurate code selection, as laterality is required for this code. Because I82.C21 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.C21 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Verify documentation specifies 'chronic' duration and 'right' side to ensure accurate code selection, as laterality is required for this code
•Investigate the underlying cause (malignancy, trauma, central line placement, hypercoagulable state) as this may require additional diagnosis codes to capture the complete clinical picture

Clinical Significance

Chronic internal jugular vein thrombosis indicates a long-standing vascular condition with persistent clot burden, reflecting ongoing risk for post-thrombotic syndrome, recurrent thromboembolism, and venous insufficiency. This diagnosis captures the sustained complexity of the patient's vascular disease and the need for long-term anticoagulation management, which is important for accurate risk adjustment.

Documentation Requirements

✓Provider documentation explicitly stating chronic embolism or thrombosis of the internal jugular vein
✓Laterality must be documented (right side) — do not assume from context
✓Clinical findings supporting the diagnosis (e.g., swelling, pain, imaging results such as duplex ultrasound or CT venography)
✓Current treatment plan including anticoagulation therapy type, duration, and monitoring parameters
✓Duration or timeline establishing chronicity (e.g., 'long-standing,' 'diagnosed 6 months ago')
✓Evidence of ongoing monitoring or follow-up imaging confirming persistent thrombus

Commonly Confused Codes

•I82.C11: Acute (not chronic) embolism and thrombosis of the right internal jugular vein; use for newly formed clots
•I82.B21: Chronic embolism and thrombosis of the right subclavian vein; different vessel near the collarbone
•I80.8: Phlebitis and thrombophlebitis of other sites; inflammatory component distinguishes this from pure thrombosis