I65.23

🧬 ICD-10-CM I65.23 — Occlusion and Stenosis of Bilateral Carotid Arteries

Billable Code Confirmed — 6-Character Code, Complete

ICD-10 CM I65.23 is a valid, billable 6-character ICD-10-CM code for FY2026. All characters confirmed: I65 (occlusion and stenosis of precerebral arteries, NOT resulting in cerebral infarction) + .2 (carotid artery) + 3 (bilateral). No placeholder X, no 7th character required — Chapter 9 circulatory codes do not carry the encounter-type 7th character system used in Chapter 19 injury codes.

Excludes1 — Critical Rule Before Assigning This Code

ICD-10 CM I65.23 CANNOT be coded alongside I63.231-I63.239 (cerebral infarction due to occlusion/stenosis of bilateral carotid arteries) for the same vessel. The Excludes1 note at I65 prohibits simultaneous assignment of I65.x and I63.0-I63.2 when the carotid stenosis IS the cause of the infarction. When bilateral carotid stenosis causes a stroke:

❌ Do NOT use: I65.23 + I63.231 ✅ Use ONLY: I63.231 (or appropriate I63.23x subcode) — the combination code captures both the stenosis AND the infarction

ICD-10 CM I65.23 is used ONLY when the stenosis/occlusion has NOT (yet) resulted in cerebral infarction.

⭐ CIC Exam Concept — Chapter 9 vs. Chapter 19

Structure

This is one of the most important structural distinctions to master for the CIC exam:

Feature	I65.23 (Chapter 9)	S02.92XA (Chapter 19)
Characters required	6 (complete)	7 (required)
Placeholder X	❌ Not used	✅ Required at position 6
7th character	❌ Not used	✅ A/B/D/G/K/S required
Encounter type	❌ Not tracked	✅ Initial/subsequent/sequela
Active vs. history	Use Z86.73 for history	Use S code with 7th char S
External cause codes	❌ Not required	✅ Required (W/X/Y series)

Chapter 9 chronic disease codes track WHAT and WHERE. Chapter 19 injury codes track WHAT, WHERE, and WHEN (in the care episode).

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🔍 Code Description

ICD-10 CM I65.23 classifies occlusion and stenosis of both the right and left carotid arteries, without resulting cerebral infarction — meaning both carotid arteries have documented narrowing (stenosis), complete or partial blockage (occlusion), or related pathology (thrombosis, embolism) that has not caused a stroke at the time of the encounter.

The carotid arteries are the primary blood supply conduits to the anterior cerebral circulation — the internal carotid arteries perfuse the frontal, parietal, and temporal lobes, as well as the ipsilateral eye via the ophthalmic artery. Stenosis or occlusion of these vessels represents a critical risk factor for ischemic stroke, and bilateral involvement significantly elevates that risk compared to unilateral disease. The diagnosis is most commonly established via carotid duplex ultrasound and confirmed with CT angiography (CTA) or MR angiography (MRA) of the neck. Management ranges from aggressive medical therapy (antiplatelet agents, statins, blood pressure control) to procedural intervention (carotid endarterectomy or carotid artery stenting) depending on degree of stenosis and symptom status.

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🌳 Code Tree / Hierarchy

I60-I69   Cerebrovascular Diseases
│
└── I65     Occlusion and Stenosis of Precerebral Arteries,
│           NOT Resulting in Cerebral Infarction ← KEY QUALIFIER
│
├── I65.0   Occlusion/Stenosis of Vertebral Artery
│   ├── I65.01  Right vertebral
│   ├── I65.02  Left vertebral
│   ├── I65.03  Bilateral vertebral ← analogous bilateral code
│   └── I65.09  Unspecified vertebral
│
├── I65.1   Occlusion/Stenosis of Basilar Artery
│
├── I65.2   Occlusion/Stenosis of Carotid Artery
│   ├── I65.21  Right carotid only
│   ├── I65.22  Left carotid only
│   ├── I65.23  BILATERAL carotid ◀ THIS CODE ✅
│   └── I65.29  Unspecified carotid ⚠️ query for laterality
│
└── I65.8   Occlusion/Stenosis of Other Precerebral Arteries
    └── I65.9   Unspecified precerebral artery
 ## When the Stenosis Causes Infarction — The Parallel I63 Family
    I63.2x  Cerebral Infarction Due to Unspecified Occlusion or
        Stenosis of Precerebral Arteries
│
└── I63.23x  Due to Unspecified Stenosis of Bilateral Carotid
    ├── I63.231  Right side dominant
    ├── I63.232  Left side dominant
    ├── I63.233  Bilateral
    └── I63.239  Unspecified

The Parallel Structure Is Not a Dual-Coding Opportunity

ICD-10 CM I65.23 and I63.23x describe the same anatomical finding (bilateral carotid stenosis) at two different clinical moments — before and after infarction occurs. They are NEVER coded together for the same vessel event. When you see I65.23, ask: “Has a stroke occurred due to this stenosis?” If yes → I63.23x replaces I65.23. If no → I65.23 is correct.

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⚠️ I65.23 vs. I63.23x — The Critical Decision Algorithm

This is the single most important coding decision point for this
code family. The clinical chart will often document BOTH carotid
stenosis AND a stroke — and the coder must determine which code(s)
to assign.

PATIENT HAS BILATERAL CAROTID STENOSIS + STROKE DOCUMENTED
                    │
                    ▼
Is the stroke (cerebral infarction) CAUSED BY the carotid
stenosis? (Check: physician attribution, radiology report,
vessel territory match, carotid as culprit lesion)
                    │
         ┌──────────┴──────────┐
         ▼                     ▼
        YES                    NO / UNCLEAR
         │                     │
         ▼                     ▼
Use I63.23x ONLY          QUERY the physician
(combination code)         to determine if
I65.23 is Excludes1        causal link exists
blocked — do NOT           │
add I65.23                 │
                           ├── Physician confirms
                           │   causal link → I63.23x only
                           │
                           └── Physician says UNRELATED
                               (e.g., infarction due to afib
                               embolus, NOT carotid stenosis)
                               → I63.x (correct infarction
                               code) + I65.23 (bilateral
                               carotid stenosis, separate
                               condition, clinically active)
                               [Excludes1 override — different
                               mechanism/vessel scenario]

The Excludes1 Override — Coding Clinic Q3 2018, P.5

The Excludes1 note at I65 does NOT mean a patient can NEVER have
both I65.23 and an I63.x code simultaneously. It means they cannot
be coded together when describing the SAME causal event. The
Coding Clinic precedent (Q3 2018 — coronary artery analogy) and
Q3 2018 direct guidance supports dual coding when:

• The cerebral infarction is caused by a different mechanism
  (e.g., cardioembolism from afib) AND

• The bilateral carotid stenosis is a separate, clinically
  significant, active condition documented as such by the physician
  AND

• The carotid stenosis is in a different vessel than the
  infarction mechanism OR clearly documented as unrelated
  Without explicit physician documentation of the causal disconnect,
  do NOT override the Excludes1. Default to querying.

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🆚 I65.23 vs. G45.x — Carotid Stenosis vs. TIA

Another critical distinction: TIA and carotid stenosis are related
but separately codeable conditions.

Code	Description	When to Use
I65.23	Bilateral carotid occlusion/stenosis, NO infarction	Stenosis documented — no TIA or stroke episode at this encounter
G45.1	Carotid artery syndrome (hemispheric TIA)	TIA episode attributed to carotid territory ischemia
G45.9	TIA, unspecified	TIA not specified by territory
I63.23x	Cerebral infarction due to bilateral carotid stenosis	Actual stroke caused by the carotid stenosis

Code Both I65.23 AND G45.x When Both Are Documented

When a patient presents with a TIA (G45.x) AND has documented
bilateral carotid stenosis (I65.23), BOTH codes may be assigned —
there is no Excludes1 interaction between I65.23 and G45.x. The
TIA and the carotid stenosis are separately codeable and clinically
distinct: TIA is the symptomatic episode; the carotid stenosis is
the underlying structural finding that places the patient at risk.
Code the reason for the visit first (TIA as principal or first-
listed, depending on setting) and I65.23 as an additional diagnosis
reflecting the active vascular condition.

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📊 Clinical Overview

Carotid Artery Anatomy — Coding Relevance

The common carotid artery (CCA) bifurcates at the level of the
thyroid cartilage (C4) into the internal carotid artery (ICA)
and the external carotid artery (ECA). For stroke risk and
I65.23 coding purposes:

Vessel	Brain Territory Perfused	Clinical Significance
Internal Carotid Artery (ICA)	Anterior cerebral artery (ACA), Middle cerebral artery (MCA), Ophthalmic artery	PRIMARY stroke risk territory; most CEA/CAS procedures target ICA stenosis at the bifurcation
External Carotid Artery (ECA)	Face, scalp, extracranial structures	Not a direct stroke risk vessel; ECA stenosis alone is clinically less significant
Common Carotid Artery (CCA)	Entire ipsilateral carotid territory	Proximal occlusion may cause massive hemispheric ischemia

ICD-10-CM Does Not Distinguish ICA vs. ECA

I65.23 applies to stenosis/occlusion of the carotid artery
system without differentiating between internal, external, and
common carotid involvement. The clinical significance (and
treatment intensity) is highest for ICA stenosis — this is
what duplex ultrasound NASCET grading primarily measures and what
drives CEA/CAS decision-making. When documentation specifies
internal carotid stenosis bilaterally, I65.23 remains the
correct code — there is no more specific ICD-10-CM code for ICA
vs. ECA vs. CCA stenosis within the I65.2x family.

NASCET Stenosis Grading — Clinical Reference for Coders

The North American Symptomatic Carotid Endarterectomy Trial
(NASCET) method is the standard for measuring ICA stenosis
severity on duplex ultrasound and angiography. Coders should
understand this grading because documentation will reference
it — and the severity tier drives treatment decisions that
generate associated CPT codes.

NASCET Grade	Stenosis %	Clinical Significance	Typical Management
Minimal	<50%	Low stroke risk	Medical management only
Moderate	50-69%	Elevated risk — symptomatic pts benefit from CEA	Medical ± CEA if symptomatic
Severe	70-99%	High stroke risk — strongest CEA benefit	CEA or CAS strongly recommended
Occlusion	100%	Complete blockage — no flow	Medical management; CEA not possible

Severity Is NOT Captured in ICD-10-CM for I65.23

Unlike some conditions where ICD-10-CM differentiates severity
(e.g., AMD staging, pressure ulcer stages), I65.23 does not
capture stenosis percentage or severity tier. Whether the patient
has bilateral 50% stenosis or bilateral 90% stenosis, the code is
the same. The NASCET grade lives in the clinical documentation
and drives CPT procedure selection — it does not change the
ICD-10-CM code assignment.

For coding purposes, what matters is:

1. Is it occlusion OR stenosis? → Same code family I65.23

2. Is it bilateral? → I65.23 (vs. I65.21/I65.22)

3. Has infarction occurred? → If yes → I63.23x, not I65.23

4. Is it symptomatic? → Symptoms (TIA, amaurosis fugax) may
   generate additional codes (G45.x, H34.x) but do not change I65.23

Pathophysiology — Why Bilateral Matters

The vast majority of carotid stenosis is caused by
atherosclerosis — lipid-rich plaque accumulation at the
carotid bifurcation, particularly the ICA origin. Bilateral
involvement typically reflects systemic atherosclerotic
disease rather than two independent localized events. Risk
factors (hypertension, hyperlipidemia, diabetes, tobacco use)
create the diffuse endothelial dysfunction that drives
simultaneous bilateral disease.

Bilateral carotid stenosis carries disproportionate stroke risk
compared to unilateral disease because:

• Collateral compensation is limited — if one carotid is
  severely stenosed, the contralateral can compensate; when both
  are stenosed, the circle of Willis is under strain from both
  anterior supply routes simultaneously

• Cerebral autoregulation may be chronically impaired —
  bilateral critical stenosis may cause hemodynamic watershed
  infarctions during even brief hypotensive episodes

• Plaque instability at two sites — each plaque is an
  independent source of thromboembolism

This clinical severity underpins why I65.23 is an important
diagnosis for documentation completeness — even though it
carries no independent HCC weight under V28, it accurately
characterizes the patient’s true vascular complexity.

Symptomatic vs. Asymptomatic Carotid Stenosis

Status	Definition	ICD-10-CM Implication
Asymptomatic	No TIA, no stroke, no amaurosis fugax attributable to carotid stenosis	I65.23 alone; code with comorbidities
Symptomatic — TIA	Transient neurological deficit <24h attributed to carotid territory ischemia	I65.23 + G45.1 or G45.9 (TIA)
Symptomatic — Amaurosis fugax	Monocular vision loss (fleeting) due to ophthalmic artery embolus from carotid plaque	I65.23 + H34.xx (retinal artery occlusion)
Symptomatic — Stroke	Cerebral infarction caused by carotid stenosis	I63.23x replaces I65.23 (Excludes1)
Post-CEA/CAS	Following surgical or endovascular treatment	I65.23 if residual/recurrent stenosis documented; Z98.8x for history of procedure

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💰 HCC Risk Adjustment — CMS-HCC v24 vs. v28

Field	CMS-HCC v24	CMS-HCC v28
HCC Category	HCC 108 — Vascular Disease	❌ Not Mapped
RAF Coefficient	~0.299	0.000
Model Status	✅ Mapped	❌ Removed from model

I65.23 Is an HCC Model Casualty Under V28

This is a direct example of the V28 restructuring impact that
every risk adjustment coder and CDI specialist needs to
understand. Under CMS-HCC V24, bilateral carotid stenosis
(I65.23 → HCC 108, ~0.299 RAF) generated meaningful risk
adjustment credit — accurately reflecting the elevated care
costs for this high-risk vascular population. Under V28
(fully operative for payment year 2026), CMS removed
uncomplicated vascular conditions from the model, arguing
that coding intensity for conditions like peripheral vascular
disease and carotid stenosis did not reliably predict
differential costs.

Practical implications:

• I65.23 alone no longer generates RAF credit in Medicare
  Advantage plans

• The risk capture burden shifts entirely to comorbidity
  documentation — DM, CAD, HF, afib, and CKD that
  co-occur in this population

• CDI teams should recognize that I65.23 encounters are
  high-yield sweeping opportunities for the conditions
  AROUND the carotid disease that do drive RAF

• If the stenosis IS complicated (has caused TIA, stroke,
  or other documented complications), ensure the most
  specific code is used — the complication may map to
  an HCC that standalone I65.23 does not

HCC Comorbidity Sweep — Bilateral Carotid Stenosis Encounters

Comorbidity	ICD-10-CM	CMS-HCC v28	Clinical Basis
Ischemic stroke / cerebral infarction	I63.x	HCC 96 — Stroke	Prior CVA with residual or active
Stroke sequelae with residual deficits	I69.3xx	HCC 96	Residual hemiparesis, aphasia, etc.
Atrial fibrillation	I48.x	HCC 96	Major concurrent embolic stroke risk
Coronary artery disease	I25.x	HCC 85	Shared atherosclerotic disease process
Congestive heart failure	I50.x	HCC 85/86	Common comorbidity
Type 2 DM with complications	E11.5x	HCC 37	Vascular DM — “with” convention applies
CKD Stage 3b-5	N18.3b-N18.5	HCC 138	Shared vascular risk
COPD	J44.x	HCC 111	Common in smokers with carotid disease
Morbid obesity	E66.01	HCC 48	Metabolic risk factor
Tobacco dependence	F17.210	No HCC but CDI value	Documents modifiable risk factor

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🏥 MS-DRG Assignment

MDC 01 — Diseases and Disorders of the Nervous System
(I65.23 routes to nervous system MDC as a cerebrovascular code)

Medical Partition (No Operative Procedure)

DRG	Title	Notes
DRG 091	Other Disorders of Nervous System with MCC	I65.23 as principal + MCC present
DRG 092	Other Disorders of Nervous System with CC	I65.23 as principal + CC present
DRG 093	Other Disorders of Nervous System without CC/MCC	I65.23 as principal, no CC/MCC

Inpatient Admission Context for I65.23

Standalone inpatient admission for asymptomatic bilateral carotid
stenosis is clinically uncommon — the diagnosis is typically
managed in the outpatient setting or is the reason for a scheduled
surgical procedure (CEA). In the inpatient setting, I65.23 most
commonly appears as:

1. Additional diagnosis during TIA admission (principal = G45.x)

2. Additional diagnosis during ischemic stroke admission
   (principal = I63.x — ensure I65.23 is NOT also coded if it is
   the causative stenosis — Excludes1)

3. Principal diagnosis in the rare admission for bilateral
   carotid stenosis workup/monitoring, especially pre-operative
   evaluation before staged bilateral CEA

4. Additional diagnosis on any medical admission where the
   patient’s cerebrovascular disease is clinically active and
   affects management

CEA/CAS Procedure DRG Routing

When CEA (carotid endarterectomy) or CAS (carotid artery stenting)
is performed, the DRG routing shifts to the surgical partition:

Procedure	ICD-10-PCS	DRG Impact
CEA — right carotid	03CK0ZZ (Extirpation, right ICA, open)	MDC 01 Surgical — verify with FY2026 grouper
CEA — left carotid	03CL0ZZ (Extirpation, left ICA, open)	MDC 01 Surgical
CAS — right carotid with stent	037K0DZ (Dilation, right ICA, intraluminal device, open)	MDC 01 Surgical
Patch angioplasty	Combined with CEA root operation	Affects DRG tier — document clearly

ICD-10-PCS Root Operation for CEA

The correct ICD-10-PCS root operation for carotid endarterectomy
is Extirpation (taking out solid matter from a body part) —
NOT Excision. The plaque being removed is the “solid matter”
(atherosclerotic debris) being extirpated from the carotid artery
lumen. This is a commonly tested inpatient coding concept. Verify
the body part character based on which specific carotid vessel
(common vs. internal vs. external) is documented in the operative
report, and confirm the approach character (0 = open for standard
CEA; 3 = percutaneous for CAS).

🛠️ CPT Procedural Crosswalk — wRVU & Assistant Payable Status

Below are the most common CPT codes associated with the evaluation, monitoring, and surgical management of I65.23.^3,4

Diagnostic / Imaging Studies

CPT Code	Description	wRVU (Facility)	Asst. Surgeon Payable?	Co-Surgeon Payable?
93880	Duplex scan of extracranial arteries; complete bilateral study	0.92	No (Indicator 0)	No (Indicator 0)
93882	Duplex scan of extracranial arteries; unilateral or limited study	0.75	No (Indicator 0)	No (Indicator 0)
70498	CT angiography, neck, with contrast material(s)	1.45 (26 component)	No (Indicator 0)	No (Indicator 0)
70548	MR angiography, neck; with contrast material(s)	1.52 (26 component)	No (Indicator 0)	No (Indicator 0)
70549	MR angiography, neck; without and with contrast	1.74 (26 component)	No (Indicator 0)	No (Indicator 0)
93886	Transcranial Doppler study of the intracranial arteries; complete study	1.20	No (Indicator 0)	No (Indicator 0)

Note: Imaging wRVU values reflect the professional component (modifier -26). Technical component is facility-billed separately. Verify current year values against the CMS Physician Fee Schedule.

Surgical Interventions

CPT Code	Description	wRVU (Facility)	Asst. Surgeon Payable?	Co-Surgeon Payable?
35301	Thromboendarterectomy, with or without patch graft; carotid, vertebral, subclavian, by neck incision	20.61	Yes (Indicator 2) — Justification required	No (Indicator 0)
35390	Reoperation, carotid thromboendarterectomy, more than 1 month after original operation	18.00	Yes (Indicator 2) — Justification required	No (Indicator 0)
37215	Transcatheter placement of intravascular stent(s), cervical carotid artery, with distal embolic protection	13.15	Yes (Indicator 2) — Justification required	No (Indicator 0)
37216	Transcatheter placement of intravascular stent(s), cervical carotid artery, without distal embolic protection	12.50	Yes (Indicator 2) — Justification required	No (Indicator 0)

Note: 35301 carries a 90-day global period. Any services rendered within 90 days of CEA that are related to the procedure must be billed with appropriate modifier (-24, -78, or -79) or are included in the global package. wRVU values are estimates — verify against the current CMS Physician Fee Schedule.

Evaluation and Management

CPT Code	Description	wRVU	Asst. Surgeon Payable?	Co-Surgeon Payable?
99213	Office/outpatient E/M, established patient — low MDM or 20-29 min	1.30	No	No
99214	Office/outpatient E/M, established patient — moderate MDM or 30-39 min	1.92	No	No
99215	Office/outpatient E/M, established patient — high MDM or 40-54 min	2.80	No	No
99204	Office/outpatient E/M, new patient — moderate MDM or 45-59 min	3.00	No	No
99205	Office/outpatient E/M, new patient — high MDM or 60-74 min	3.50	No	No
99252	Inpatient or observation consult — low MDM	1.52	No	No
99253	Inpatient or observation consult — moderate MDM	2.79	No	No
99254	Inpatient or observation consult — high MDM	3.69	No	No

E/M Medical Decision Making — I65.23 Encounter Complexity

Bilateral carotid stenosis management typically supports moderate to high MDM at E/M encounters due to:

• Prescription drug management (antiplatelet, statin, antihypertensive)
• Review and interpretation of imaging studies (duplex, CTA/MRA)
• Independent interpretation of new test results (duplex at each surveillance visit)
• Data review with ordering of additional tests (if symptoms change)
• Risk stratification decisions (watchful waiting vs. referral for CEA/CAS)

A vascular surgeon or neurologist managing bilateral carotid stenosis with duplex review, medication adjustment, and symptom assessment at the same visit has strong documentation support for 99214 or 99215 depending on MDM tier. Document the number of problems, data reviewed, and risk of management explicitly.

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💊 Coding Scenarios

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Scenario 1 — Surveillance Duplex, Outpatient Vascular Surgery Clinic

Clinical Vignette: A 70-year-old male with known bilateral carotid stenosis presents to the vascular surgery clinic for his 6-month surveillance appointment. No new neurological symptoms. Carotid duplex scan is performed and interpreted today: right ICA stenosis 65-70%, left ICA stenosis 55-60%. Physician reviews results, adjusts atorvastatin dose, and counsels patient on stroke warning signs. Assessment: bilateral carotid artery stenosis, stable; hypertension; hyperlipidemia.

CPT / HCPCS:

• 99214-25 — Established patient office visit, moderate MDM (modifier -25 required if duplex is also billed same day — separately identifiable E/M service)
• 93880 — Duplex scan of extracranial arteries, bilateral (both carotids evaluated; bilateral code correct; interpret and document findings in the report to support separate billing)

ICD-10-CM:

• I65.23 — Occlusion and stenosis of bilateral carotid arteries (principal/first-listed — reason for visit)
• I10 — Essential hypertension (active comorbidity, managed at this visit)
• E78.5 — Hyperlipidemia, unspecified (active comorbidity — statin adjusted)

Modifier -25 Requirement — E/M + Duplex Same Day

When the physician performs AND interprets the carotid duplex (93880) AND conducts a separately identifiable E/M visit (99214) on the same date of service, modifier -25 must be appended to the E/M code — NOT to the imaging code. The modifier signals that the E/M was a significant, separately identifiable service above and beyond the pre/post-service work of the duplex. The medical record must support a distinct E/M service (history, examination, MDM documented separately from the imaging interpretation note). Without modifier -25, the payer will bundle the E/M into the imaging code and deny the E/M.

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Scenario 2 — Pre-Operative CEA Admission for Symptomatic Bilateral Carotid Stenosis

Clinical Vignette: A 67-year-old female with bilateral carotid stenosis (right ICA 80%, left ICA 65%) and a recent right-sided TIA (fully resolved, 3 weeks prior) is admitted for elective right CEA. Pre-op CTA neck confirms stenosis severity. Surgery performed without complications — right CEA with bovine patch angioplasty. Discharge summary: “Right carotid stenosis, symptomatic (recent TIA), status post right CEA. Left carotid stenosis, asymptomatic, 65% — plan for surveillance and staged left CEA in 6-8 weeks.”

CPT / HCPCS:

• 35301 — Thromboendarterectomy, carotid, by neck incision (right side; facility and professional claims; 90-day global period begins this date)
• 70498-26 — CTA neck with contrast, professional component (pre-operative imaging; billed on date performed)

ICD-10-CM:

• I65.21 — Occlusion and stenosis of right carotid artery (principal diagnosis — reason for admission and surgical procedure)
• G45.1 — Carotid artery syndrome (hemispheric TIA) (recent symptomatic event that drove surgical decision — additional diagnosis)
• I65.22 — Occlusion and stenosis of left carotid artery (additional — documented active condition, separately managed; NOT bilateral I65.23 because the two sides are at different treatment stages at the time of this admission)
• I10 — Essential hypertension
• E78.5 — Hyperlipidemia

Why Separate Laterality Codes Instead of I65.23 Here?

I65.23 (bilateral) is appropriate when both carotid stenoses are being managed as a unified bilateral condition. In this scenario, the right stenosis is the operative target (principal diagnosis) and the left stenosis is a separate ongoing condition being monitored for future staged intervention. Using I65.21 + I65.22 accurately reflects the distinct management status of each vessel at this specific encounter. Using I65.23 alone would obscure the laterality-specific surgical context — and the ICD-10-PCS procedure code (Extirpation, right ICA) also reflects unilateral operative work.

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Scenario 3 — Bilateral Carotid Stenosis Discovered on TIA Workup (ED/Inpatient)

Clinical Vignette: A 74-year-old male presents to the ED with 20 minutes of left arm weakness and dysarthria that fully resolved. MRI brain: no acute infarct. CTA head/neck: no intracranial pathology; bilateral ICA stenosis right 70%, left 55%. Neurology consulted. Admit for TIA workup and monitoring. Final diagnosis: “Left hemisphere TIA. Bilateral carotid stenosis. Initiate dual antiplatelet therapy and high-intensity statin. Vascular surgery referral for CEA evaluation.”

CPT / HCPCS:

• 99253 or 99254 — Inpatient consultation, neurology (moderate to high MDM — TIA with bilateral carotid stenosis, new prescription management, referral decision)
• 70498-26 — CTA neck with contrast, professional component
• 93886 — Transcranial Doppler (if performed to evaluate intracranial hemodynamics)

ICD-10-CM (Principal = Reason for Admission):

• G45.1 — Carotid artery syndrome, hemispheric TIA (principal — acute symptomatic event driving the admission; fully resolved, no infarction confirmed on MRI)
• I65.23 — Occlusion and stenosis of bilateral carotid arteries (additional — bilateral stenosis identified on CTA, documented as clinically active and driving management decisions)
• I10 — Hypertension
• E78.5 — Hyperlipidemia
• Z79.02 — Long-term use of antithrombotic/antiplatelet agents (if dual antiplatelet initiated and documented)

TIA + Bilateral Carotid Stenosis — No Excludes1 Conflict

G45.1 (TIA) + I65.23 (bilateral carotid stenosis) may be coded together without restriction. There is no Excludes1 interaction between the G45.x TIA family and the I65.x stenosis family. TIA is a transient neurological event — it does not constitute cerebral infarction (I63.x), and therefore the Excludes1 note at I65 is not triggered. Always capture both codes when both are documented — the TIA as the reason for the acute encounter and I65.23 as the underlying structural finding that explains the mechanism and drives ongoing management.

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Scenario 4 — Carotid Stenting (CAS) for High Surgical Risk Patient

Clinical Vignette: A 78-year-old female with severe COPD (FEV1 45% predicted), recent MI (4 weeks ago), and bilateral carotid stenosis (right ICA 85%, left ICA 72%) is deemed high surgical risk for CEA by the vascular surgery team. Interventional radiology performs right carotid artery stenting with embolic protection device under general anesthesia. Procedure technically successful. Discharge diagnosis: “Right carotid artery stenosis, high surgical risk, status post right CAS with embolic protection. Left carotid stenosis 72%, asymptomatic — surveillance plan.”

CPT / HCPCS:

• ICD-10 CM 37215 — Transcatheter placement of intravascular stent(s), cervical carotid artery, open or percutaneous, with distal embolic protection (right side; document embolic protection device use explicitly in the operative note to support 37215 over 37216)

ICD-10-CM:

• I65.21 — Occlusion and stenosis of right carotid artery (principal — operative target)
• I65.22 — Occlusion and stenosis of left carotid artery (additional — active untreated condition)
• J44.1 — COPD with acute exacerbation (or J44.0/J44.9 based on current status — documents high surgical risk basis)
• I25.2 — Old myocardial infarction (recent MI — basis for high surgical risk determination)
• I10 — Hypertension

37215 vs. 37216 — Embolic Protection Documentation

The difference between 37215 (with embolic protection) and 37216 (without embolic protection) carries significant reimbursement implications — 37215 has a higher wRVU. CMS and most payers expect embolic protection to be used in virtually all cervical CAS procedures for stroke risk reduction. If 37216 is billed, expect scrutiny — the operative report MUST explicitly document the reason embolic protection was not used (e.g., severe vessel tortuosity, vessel anatomy incompatible with filter deployment). Do not code 37216 simply because the embolic protection device is not mentioned — query the physician. The default in contemporary practice is 37215.

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Scenario 5 — Staged Bilateral CEA: Second Side During Global Period

Clinical Vignette: A 71-year-old male underwent right CEA (CPT 35301) six weeks ago. He now returns for the planned staged left CEA. Left ICA stenosis 75%, asymptomatic. The second surgery was planned and documented as a staged procedure at the time of the first CEA. Procedure completed without complications.

CPT / HCPCS:

• 35301--58 — Thromboendarterectomy, carotid; modifier -58 appended (staged or related procedure during postoperative global period; planned at the time of the initial procedure; returns the procedure to a new global period)

ICD-10-CM:

• I65.22 — Occlusion and stenosis of left carotid artery (principal — operative indication for this encounter)
• Z48.812 — Encounter for surgical aftercare following surgery on the circulatory system (if applicable — post-op context)
• I10 — Hypertension
• E78.5 — Hyperlipidemia

Modifier -58 vs. -79 for Staged Bilateral CEA

Modifier selection for the second-side CEA within the global period of the first depends entirely on whether the second procedure was planned at the time of the original:

Scenario	Modifier	Rationale
Second CEA was planned and documented as staged at time of first	-58	Staged/related procedure; new global period begins
Second CEA was not planned — new clinical indication arose	-79	Unrelated procedure during postop period; new global begins
Patient returns to OR for complication of the first CEA	-78	Return to OR for related complication; does NOT start new global

Documentation in the original operative report AND the preoperative note for the second procedure must both reference the planned staged nature to support modifier -58. Without explicit “staged bilateral CEA” language in both records, the payer has grounds to deny or downcode the second procedure claim.

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⚠️ Coding Pitfalls and Tips

	Pitfall or Tip
❌	Never code I65.23 alongside I63.231-I63.239 for the same vessel-cause event — Excludes1 applies; when bilateral carotid stenosis causes cerebral infarction, I63.23x is the correct combination code and supersedes I65.23; adding both is double-coding the same causal event and will trigger NCCI edits
❌	Never assume the carotid stenosis caused the stroke without explicit physician documentation — do not apply the “With” convention to automatically link I65.23 to an I63.x infarction code; query when causal attribution is undocumented; default to querying before overriding Excludes1
❌	Never use I65.29 (unspecified carotid) when laterality is documented — bilateral involvement is captured by I65.23; I65.29 is a last-resort code for truly undocumented laterality; query before defaulting to unspecified
❌	Do not add a 7th character or placeholder X to I65.23 — this is a 6-character Chapter 9 chronic disease code; it does not use the encounter-type 7th character system (A/D/S) or fracture healing characters (D/G/K) from Chapter 19; the code is structurally complete as written
❌	Do not append external cause codes (W/X/Y) to I65.23 — external cause coding applies to Chapter 19 injury and trauma codes only; I65.23 is a chronic pathological vascular condition, not a traumatic injury
❌	Do not omit modifier -25 when billing E/M + duplex on the same date — the E/M (99213-99215) and carotid duplex (93880) are separately billable on the same DOS only when modifier -25 is on the E/M; without it, payers will bundle and deny the E/M as included in the imaging service
❌	Do not use 37216 (CAS without embolic protection) without explicit operative documentation of why protection was not used — in the absence of documented contraindication, the expectation is 37215; undocumented omission of embolic protection is a compliance risk and a claim denial trigger
✅	Code bilateral I65.23 over two separate laterality codes when both carotids are equally active and undifferentiated — I65.23 is more specific than I65.21 + I65.22 when bilateral disease is the unified clinical finding; exception: when the two sides are at different management stages in the same encounter, use separate laterality codes to reflect the differential clinical status
✅	Code TIA (G45.x) separately alongside I65.23 when both are documented — there is no Excludes1 interaction between I65.23 and G45.x; both codes should be captured; the TIA is the symptomatic episode and I65.23 is the underlying structural finding
✅	Use I65.23 as a comorbidity sweep trigger at every encounter — while I65.23 carries no HCC weight under CMS-HCC v28, the patient population almost universally carries HCC-bearing comorbidities (CAD, DM, afib, CKD, HF) that do drive RAF; capture every active condition that meets UHDDS criteria at every encounter
✅	Verify modifier -58 documentation for staged bilateral CEA — the planned staged nature of the second CEA must be documented in BOTH the original operative note AND the second preoperative documentation to withstand audit; “staged bilateral CEA” language in both records is the minimum documentation standard
✅	For ICD-10-PCS, use Extirpation (root operation C) for CEA — NOT Excision; the plaque being removed is “solid matter” being taken out of the carotid artery lumen; Extirpation is the correct root operation; this is a high-yield inpatient coding concept for the CIC exam

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📚 Sources

1. CMS/NCHS. *ICD-10-CM Official Guidelines for Coding and Reporting, FY2026. Section I.C.9 — Cerebrovascular disease coding guidelines; “With” convention application and limitations; Excludes1 note interpretation and override criteria; principal diagnosis selection (Section II); code to highest degree of specificity (Section I.B.3); additional diagnosis reporting criteria — UHDDS definition of “other diagnoses” (Section III).

2. CMS/NCHS. ICD-10-CM Tabular List FY2026. I65 — Occlusion and Stenosis of Precerebral Arteries, Not Resulting in Cerebral Infarction; I65.2 — Carotid artery family; I65.21-I65.29 billable code entries and laterality character definitions; Excludes1 interactions with I63.0-I63.2; Use Additional Code instructions; G45.x — TIA coding and interaction with I65.x.

3. American Medical Association (AMA). CPT 2026 Professional Edition. Surgery — Cardiovascular System: Arteries and Veins — CEA (35301, 35390); Endovascular Revascularization — CAS (37215, 37216); global period determinations; staged procedure modifier -58 guidance. Radiology — Diagnostic Ultrasound: Vascular studies (93880, 93882, 93886); CTA/MRA neck (70498, 70548, 70549).

4. CMS. Physician Fee Schedule Final Rule FY2026. wRVU values for 35301, 37215, 37216, 93880, 93882, 70498, 70548, 99213-99215, 99204-99205, 99252-99254; 90-day global period confirmation for CEA (35301); assistant surgeon payable indicators; professional vs. technical component billing guidelines (modifier -26, -TC).

5. CMS. *National Correct Coding Initiative (NCCI) Policy Manual for Medicare Services, current version. Cardiovascular Surgery chapter — CEA and endovascular bundling rules; E/M modifier -25 requirements for same-day vascular imaging and office visit; bilateral procedure billing guidance (modifier -50, -RT/-LT); staged procedure modifier -58 vs. -78 vs. -79 definitions and documentation requirements.

6. CMS. IPPS Final Rule FY2026 — MS-DRG Definitions Manual v43. MDC 01 — Diseases and Disorders of the Nervous System; DRGs 091-093 (medical partition); CC/MCC assignment for cerebrovascular diagnoses; POA indicator requirements for cerebrovascular disease in the inpatient setting.

7. CMS. ICD-10-PCS Reference Manual FY2026. Section 0 (Medical & Surgical), Body System 3 (Upper Arteries) — Root operation C (Extirpation) for CEA; body part characters K (right ICA) and L (left ICA); approach character 0 (open); device character Z (no device); qualifier Z (no qualifier); contrast between Extirpation (CEA) and Dilation (CAS/angioplasty, root operation 7) with intraluminal device character D.

8. American Heart Association / American Stroke Association. 2021 Guideline for the Prevention of Stroke in Patients with Stroke and Transient Ischemic Attack. Carotid stenosis management — CEA vs. CAS eligibility criteria; NASCET stenosis grading; symptomatic vs. asymptomatic threshold recommendations; dual antiplatelet therapy and high-intensity statin protocols. Stroke. 2021;52(7):e364-e467.

9. Society for Vascular Surgery (SVS). Clinical Practice Guidelines for Management of Extracranial Cerebrovascular Disease. Carotid duplex surveillance protocols; bilateral stenosis management algorithms; staging recommendations for bilateral CEA; medical management of asymptomatic carotid stenosis. Journal of Vascular Surgery. 2022;75(1S):4S-22S.

10. AAPC. ICD-10-CM Professional Coding Manual FY2026. Chapter 9 cerebrovascular disease coding — I65.x occlusion/stenosis family; I63.x cerebral infarction combination codes; Excludes1 override scenarios for vascular disease with concurrent infarction of different mechanism; TIA coding with concurrent carotid stenosis; “With” convention cautions for Chapter 9.

11. CMS. Coding Clinic for ICD-10-CM and ICD-10-PCS.Q3 2018, p.5 — Excludes1 override guidance for concurrent vascular disease and cerebral infarction of different mechanisms. Q2 2023 — Causal relationship attribution in cerebrovascular disease; physician documentation requirements for I63.x combination code assignment vs. separate I65.x + I63.x coding.