Usg doppler bilateral lower limb interpretation in very detail
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USG Doppler bilateral lower limb arterial venous waveform interpretation
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peripheral arterial disease PAD ankle brachial index ABI Doppler waveform triphasic biphasic monophasic
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DVT deep vein thrombosis compression ultrasound non-compressible vein thrombus
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Here is a comprehensive guide to USG Doppler Bilateral Lower Limb Interpretation, covering both arterial and venous systems in detail.
USG Doppler Bilateral Lower Limb — Detailed Interpretation Guide
PART 1: TECHNICAL BASICS
Modes Used
| Mode | Purpose |
|---|---|
| B-mode (Greyscale) | Vessel wall, lumen, compressibility, thrombus echogenicity |
| Color Doppler | Flow direction, patency, turbulence |
| Power Doppler | Sensitive low-flow detection (no directional info) |
| Spectral (Pulsed Wave) Doppler | Waveform analysis, velocity measurements |
| Continuous Wave Doppler | High-velocity stenosis (less commonly used) |
Patient Positioning
- Arterial study: Supine; leg slightly externally rotated. Popliteal artery: prone or lateral decubitus
- Venous study: Supine with legs slightly dependent (Trendelenburg reversed) to distend veins; or sitting upright for calf veins
Transducer Selection
- Linear high-frequency (7–15 MHz): Superficial femoral, popliteal, tibial vessels, veins
- Curvilinear (3–5 MHz): Aortoiliac segment, obese patients
PART 2: ARTERIAL DOPPLER — BILATERAL LOWER LIMB
2.1 Vessels Examined (Proximal → Distal)
| Segment | Vessels |
|---|---|
| Aortoiliac | Distal aorta, common iliac artery |
| Thigh | Common femoral artery (CFA), profunda femoris, superficial femoral artery (SFA) |
| Knee | Popliteal artery |
| Leg | Anterior tibial artery (ATA), posterior tibial artery (PTA), peroneal artery |
| Foot | Dorsalis pedis artery (DPA) |
2.2 Normal Arterial Waveform — Triphasic Pattern
A normal peripheral artery at rest has a triphasic (high-resistance) waveform with three distinct components:
- Phase 1 — Forward systolic peak: Rapid high-amplitude upstroke during ventricular systole
- Phase 2 — Brief reverse diastolic flow: Due to peripheral arterial elasticity and vasoconstriction (a small below-baseline deflection)
- Phase 3 — Forward low-velocity late diastolic flow: Elastic recoil of arterial wall propels a small second forward wave
Biphasic waveform: Loss of phase 3 — still normal in elderly or during exercise/warmth (vasodilation)
Monophasic waveform: Loss of phases 2 and 3 — indicates proximal stenosis or obstruction (parvus-tardus pattern)
2.3 Arterial Waveform Changes with Disease
Left: Normal triphasic waveforms with equal bilateral pressures (ABI ~1.0) vs stenotic side with progressively dropping segmental pressures and flattened monophasic waveforms (ABI 0.32). Right: ABI measurement technique using Doppler probe and cuff.
Clinical ischemic ulcer (left) with corresponding Doppler showing loss of triphasic pattern — delayed systolic upstroke and monophasic flow indicating suprapopliteal stenosis.
| Waveform | Appearance | Significance |
|---|---|---|
| Triphasic | 3 peaks; reverse diastolic component present | Normal high-resistance peripheral artery |
| Biphasic | 2 peaks; reverse component absent | Elderly, vasodilated, or mild disease |
| Monophasic | Single broad peak; no reverse flow | Significant proximal stenosis/occlusion |
| Parvus-tardus | Low amplitude + slow systolic rise time | Classic for proximal stenosis (e.g., iliac occlusion) |
| Spectral broadening | Waveform fills below baseline curve | Turbulent flow at or distal to stenosis |
2.4 Velocity Criteria for Stenosis
| Finding | Significance |
|---|---|
| Peak systolic velocity (PSV) ratio >2:1 (stenotic:prestenotic) | ≥50% diameter stenosis |
| PSV ratio >4:1 | ≥75% stenosis |
| PSV at stenosis >200 cm/s with ratio >2 | Hemodynamically significant stenosis |
| No detectable flow on Color + Spectral Doppler | Occlusion |
| Collateral waveforms (low-velocity, monophasic) | Chronic occlusion with collateral formation |
2.5 Ankle-Brachial Index (ABI)
Measured with a continuous-wave Doppler probe and blood pressure cuff:
ABI = Ankle systolic pressure ÷ Brachial systolic pressure
Use the higher of posterior tibial and dorsalis pedis pressures at each ankle; use higher arm pressure for denominator.
| ABI | Interpretation |
|---|---|
| >1.3 | Non-compressible vessels (medial calcification — diabetes, CKD); unreliable |
| 1.0–1.3 | Normal |
| 0.9–1.0 | Borderline |
| 0.7–0.9 | Mild PAD |
| 0.4–0.7 | Moderate PAD (claudication) |
| <0.4 | Severe PAD / critical limb ischemia |
2.6 Specific Arterial Pathologies
Peripheral Arterial Disease (PAD)
- Plaque: hyperechoic/heterechoic wall thickening on B-mode
- Post-stenotic turbulence: color aliasing, spectral broadening
- Occlusion: absent color fill + no Doppler signal; collaterals visible
- Bilateral comparison is key — asymmetric PSV ratio or waveform change indicates disease
Popliteal Artery Aneurysm
- Focal dilatation >8 mm (or 1.5× diameter of adjacent segment)
- May contain mural thrombus; risk of distal embolization
Aortoiliac Occlusion (Leriche Syndrome)
- Bilateral monophasic/absent CFA signals
- Bilateral thigh claudication + impotence
PART 3: VENOUS DOPPLER — BILATERAL LOWER LIMB
3.1 Vessels Examined
| Segment | Veins |
|---|---|
| Groin | Common femoral vein (CFV), great saphenous vein (GSV) junction |
| Thigh | Femoral vein (FV), profunda femoris vein |
| Popliteal fossa | Popliteal vein (PopV), small saphenous vein (SSV) junction |
| Leg | Posterior tibial veins (PTVs), peroneal veins, anterior tibial veins, gastrocnemius/soleal veins |
3.2 Normal Venous Criteria — "SCAPR" Mnemonic
| Feature | Normal Finding |
|---|---|
| S — Spontaneous flow | Flow present without augmentation in proximal veins (femoral, popliteal) |
| C — Compressibility | Vein collapses completely with gentle transducer pressure |
| A — Augmentation | Flow increases with distal limb compression or Valsalva release |
| P — Phasicity | Flow varies with respiration (increases with expiration in legs) |
| R — Reflux absent | No retrograde flow >0.5 s on augmentation/Valsalva |
3.3 Normal Venous Spectral Waveform
- Spontaneous, phasic (respiratory phasicity): Flow decreases/stops with inspiration (when intra-abdominal pressure rises) and increases with expiration
- Low-velocity, continuous or gently undulating
- Augments briskly with distal compression (calf squeeze)
Panel A: Normal superficial femoral artery (orange/red color flow). Panel B: Normal common femoral vein (CFV) with color Doppler blue signal + spectral waveform showing phasic respiratory variation — classic normal venous flow pattern.
3.4 Deep Vein Thrombosis (DVT) — Key Findings
Primary Sign
Non-compressibility — the most specific and sensitive criterion:
- Normal vein completely collapses when compressed
- Thrombosed vein fails to collapse
Left (NON COMP): Common femoral vein (CFV) with arrow pointing to echogenic intraluminal thrombus, adjacent to common femoral artery (CFA). Right (COMP): Vein remains non-compressible — confirming acute/chronic DVT. CFA, as expected, is non-compressible regardless.
Secondary Signs
| Sign | Finding |
|---|---|
| Intraluminal echoes | Echogenic material within vein lumen |
| Vein distension | Thrombus expands lumen compared to artery |
| Absent color flow | No color fill within thrombosed segment |
| Absent/reduced phasicity | Loss of respiratory variation |
| Absent augmentation | No flow increase with distal compression |
| Continuous (non-phasic) flow | Proximal obstruction (iliac occlusion) |
Acute vs Chronic Thrombus
| Feature | Acute DVT | Chronic DVT |
|---|---|---|
| Echogenicity | Hypoechoic/anechoic (soft) | Hyperechoic (bright, calcified) |
| Vein lumen | Distended | Contracted/irregular |
| Wall | Smooth | Thickened, irregular |
| Compressibility | Partially compressible | Rigid, non-compressible |
| Flow | Absent or marginal | Recanalized channels may appear |
| Collaterals | Uncommon | Common |
3.5 Chronic Venous Insufficiency (CVI) / Reflux
Venous reflux = retrograde (reverse) flow after augmentation or Valsalva
Normal: Reverse flow cessation within 0.5 s in superficial veins; 1.0 s in deep veins
Abnormal (reflux): Retrograde flow >0.5 s (superficial/perforators) or >1.0 s (deep veins)
| Vein | Threshold for Reflux |
|---|---|
| Great saphenous vein (GSV) | >0.5 s |
| Small saphenous vein (SSV) | >0.5 s |
| Perforator veins | >0.5 s + >3.5 mm diameter |
| Femoral vein | >1.0 s |
| Popliteal vein | >1.0 s |
Clinical Correlation (CEAP Classification):
- C0–C1: No visible disease / telangiectasias
- C2: Varicose veins
- C3: Edema
- C4a/b: Skin changes (lipodermatosclerosis, eczema)
- C5: Healed venous ulcer
- C6: Active venous ulcer
PART 4: BILATERAL COMPARISON — REPORTING STRUCTURE
A standard bilateral lower limb Doppler report addresses:
Arterial Section
- Waveform morphology at each level (triphasic / biphasic / monophasic)
- PSV values at CFA, SFA proximal/mid/distal, popliteal, ATA, PTA bilaterally
- PSV ratios at any stenotic segment
- B-mode: plaque, calcification, aneurysmal dilatation
- ABI (right and left, with individual vessel pressures)
- Impression: Normal / PAD grade / Level of disease (inflow vs. outflow vs. infrainguinal)
Venous Section
- Compressibility at every level (CFV → FV → PopV → calf veins)
- Spontaneous flow and phasicity
- Augmentation response
- Reflux testing (if varicosities or CVI suspected)
- B-mode thrombus characteristics (if DVT identified)
- Impression: No DVT / Acute DVT (site/extent) / Chronic DVT / Reflux (site/grade)
PART 5: BILATERAL LOWER LIMB STUDY — BILATERAL POSTERIOR TIBIAL ARTERIES
Bilateral duplex at ankle level: Left PTAI (top) — normal biphasic waveform, sharp systolic peak, ~60 cm/s PSV. Right PTAI (bottom) — diminished waveform amplitude suggesting asymmetric flow. Such side-to-side PSV comparison guides localization of disease.
PART 6: PITFALLS AND LIMITATIONS
| Pitfall | Solution |
|---|---|
| Calcified vessels (diabetics, elderly) — ABI >1.3 | Use toe-brachial index (TBI <0.7 = abnormal) |
| Non-visualized tibial veins (edema/obesity) | Increase compression force; use lower frequency |
| Isolated calf DVT missed on 2-point compression | Whole-leg ultrasound protocol |
| Hyperechoic acute thrombus mistaken for normal | Always confirm with compression; use color + spectral |
| Absent phasicity in normal patient (obese) | Repeat with Valsalva or positional changes |
| Overlying bowel gas for iliac vessels | CT angiography when ultrasound inconclusive |
SUMMARY TABLE
| Parameter | Arterial (Normal) | Venous (Normal) | Abnormal Finding |
|---|---|---|---|
| Waveform | Triphasic | Phasic, low-velocity | Monophasic / Non-phasic |
| Compressibility | N/A (arteries do not compress) | Complete collapse | Partial/no collapse → DVT |
| Color fill | Complete | Complete | Absent → occlusion |
| PSV | Segment-specific normal ranges | Low (<30 cm/s) | >2× step-up → stenosis |
| Reflux | None | None | >0.5–1.0 s → CVI |
| ABI | 0.9–1.3 | N/A | <0.9 → PAD |
This covers the complete systematic approach to bilateral lower limb Doppler interpretation — from normal physiology and waveform patterns to pathological findings in PAD, DVT, and chronic venous insufficiency.
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