CPT® Code 93970

Quick Reference: CPT 93970 (Complete Bilateral Venous Duplex)

• Code definition: CPT 93970 describes a duplex scan of extremity veins including responses to compression and other maneuvers; complete bilateral study. It requires full gray-scale (B-mode), color Doppler, and spectral Doppler evaluation of both extremities (arms or legs).
• Complete means complete: All required deep venous segments must be evaluated bilaterally with compression and Doppler analysis. If the study is unilateral or incomplete, report 93971 instead.
• Mutually exclusive coding: 93970 (complete bilateral) and 93971 (limited/unilateral) should not be reported together for the same extremity study in one encounter. Use the code that reflects the most comprehensive service performed.
• Medical necessity is diagnosis-driven: Medicare coverage under LCD L35451 requires documentation of appropriate clinical indications such as suspected DVT, chronic venous insufficiency, post-thrombotic syndrome, or unexplained limb swelling.
• Professional vs technical components: 93970 may be billed globally or split using modifiers 26 (professional) and TC (technical) according to Medicare radiology billing rules.
• Arterial + venous same-day restrictions: Medicare policy limits billing of extremity venous duplex studies with certain arterial duplex codes on the same date of service unless separately justified and supported by distinct diagnoses.

1. Code Definition & Clinical Scope

CPT 93970 is defined as: “Duplex scan of extremity veins including responses to compression and other maneuvers; complete bilateral study.” The official Medicare billing and coding article for Peripheral Venous Ultrasound (A52993), linked to LCD L35451, reiterates that 93970 represents a complete duplex evaluation of veins in both extremities of the same anatomic region (both upper or both lower).

A duplex study requires integration of:

• Gray-scale (B-mode) imaging,
• Color Doppler flow mapping, and
• Spectral Doppler waveform analysis.

CMS LCD materials and reconsideration documentation for L35451 emphasize that omission of required elements or venous segments downgrades the exam to a limited study.

Clinical Indications

93970 is most commonly performed for:

• Suspected acute deep venous thrombosis (DVT),
• Chronic venous insufficiency and reflux evaluation,
• Post-thrombotic syndrome assessment,
• Unexplained bilateral extremity swelling,
• Pre-procedural vein mapping (when bilateral complete evaluation is medically required).

For lower extremity studies, typical venous segments include:

• Common femoral vein
• Femoral (superficial femoral) vein
• Popliteal vein
• Great saphenous vein (when clinically relevant)

For upper extremities:

• Subclavian vein
• Axillary vein
• Brachial veins
• Basilic and cephalic veins

The study must document compressibility and Doppler flow characteristics in each required segment. ACR vascular ultrasound exam requirements reinforce the need for comprehensive documentation of flow direction and Doppler analysis in venous examinations.

If the documentation does not support a complete bilateral evaluation, 93970 is not appropriate.

2. 93970 vs 93971: Bilateral vs Limited/Unilateral

Medicare policy clearly distinguishes:

• 93970 – Complete bilateral duplex study
• 93971 – Limited bilateral or complete unilateral study

CMS Article A52993 explicitly states that 93971 is used when the study is unilateral or otherwise limited, and 93970 should not be used when criteria for complete bilateral evaluation are not met.

MedLearn Radiology guidance clarifies that if all four extremities are studied (upper and lower), separate codes may be appropriate, often requiring modifier 59 on the second study to indicate a distinct anatomic region.

However, 93970 and 93971 should not be reported together for the same lower or upper extremity encounter.

3. Medical Necessity & ICD-10 Support

Medicare coverage is governed by LCD L35451 and its associated billing article A52993. Coverage is contingent upon documentation of medical necessity.

Common ICD-10 categories that support 93970 include:

• I80.x – Phlebitis and thrombophlebitis
• I82.x – Acute embolism and thrombosis of deep veins
• I87.2 – Chronic venous insufficiency
• I87.0x – Post-thrombotic syndrome
• R22.4x – Localized swelling of limb

The CMS billing article provides specific ICD-10 codes recognized for coverage determination. Use of nonspecific diagnosis codes without clinical justification may result in denial.

Medical necessity must show:

• Symptoms (pain, swelling, erythema),
• Risk factors (recent surgery, malignancy, immobility),
• Abnormal prior imaging, or
• Follow-up of documented venous pathology.

Routine screening without signs or symptoms is generally not covered.

4. Medicare Coverage & Billing Rules

LCD Enforcement

LCD L35451 and Article A52993 establish that:

• Only one venous duplex per extremity region per encounter is typically payable.
• Extremity venous duplex studies are subject to frequency and diagnosis scrutiny.
• Venous and arterial duplex studies of extremities are restricted when billed on the same day without distinct indications.

Arterial Study Conflicts

Commercial payer edit rules (e.g., EmblemHealth) specify that venous duplex codes 93970–93971 are not payable with arterial duplex codes (93922–93931) unless separate medical necessity exists.

In practice:

• If both arterial and venous studies are done, each must be supported by distinct clinical diagnoses.
• Improper dual billing is a common denial trigger.

Professional vs Technical Billing

According to the Medicare Claims Processing Manual, Chapter 13 (Radiology Services), diagnostic ultrasound services may be billed globally or split using modifiers 26 and TC.

• 93970-26 – Physician interpretation only
• 93970-TC – Technical component only

Both components must be fully supported by documentation.

5. Modifier Use (26, TC, 59)

Modifier 26

Used when only professional interpretation is billed. Requires:

• Signed final report
• Findings and impression
• Evidence of physician review

Modifier TC

Used by facilities or IDTFs billing only the technical portion.

Modifier 59

Applied when:

• Separate venous studies are performed on distinct anatomic regions (e.g., upper and lower extremities), and
• Documentation supports non-overlapping services.

MedLearn Radiology guidance illustrates appropriate use of modifier 59 when multiple extremity duplex exams are performed on different regions the same day.

Modifier misuse—particularly applying 59 to bypass bundling edits without clear anatomic distinction—is a known audit trigger.

6. Documentation Standards (ACR & CMS Expectations)

ACR Vascular Ultrasound exam requirements emphasize:

• Documentation of compression in transverse plane,
• Color Doppler confirmation of flow,
• Spectral Doppler waveform analysis,
• Identification of venous segments examined.

CMS policy requires retention of images and documentation of both normal and abnormal findings.

Minimum report elements:

• Side (right/left/bilateral)
• Venous segments evaluated
• Compressibility findings
• Presence or absence of thrombus
• Flow direction and waveform characteristics
• Final signed impression

Failure to document compression or Doppler waveforms may result in downcoding to 93971 or claim denial.

7. Real-World Clinical Scenarios

Scenario 1: Bilateral DVT Evaluation

Patient presents with bilateral lower extremity swelling. Complete duplex exam of both legs performed. All required venous segments documented. Acute thrombus found in left popliteal vein.

Coding: 93970 Diagnosis: I82.x (acute DVT) Modifiers: None (unless split billing)

Scenario 2: Unilateral Leg Pain

Right leg evaluated only. Left leg not imaged.

Coding: 93971 Diagnosis: R22.41 (right lower limb swelling)

Scenario 3: Separate Upper and Lower Extremity Studies

Patient evaluated for suspected upper extremity thrombosis and lower extremity swelling same day.

Coding: 93970 (lower extremities) + 93970-59 (upper extremities), if both complete and medically justified.

8. Common Denial & Audit Risk Patterns

• Billing 93970 when only one limb examined
• Missing Doppler waveform documentation
• Arterial and venous duplex billed without distinct diagnoses
• Failure to document compression maneuvers
• Using modifier 59 without anatomic separation

Auditors frequently compare:

• Report narrative
• Stored images
• Diagnosis codes submitted

Mismatch between documentation and code selection is the most common reason for recoupment.