Peripheral Vascular Imaging

Modalities - Pixel Power

• Doppler Ultrasound (DUS):
  • First-line, non-invasive, real-time haemodynamics.
  • B-mode (morphology), Color & Spectral Doppler (flow).
  • Limitations: operator skill, obesity, vessel calcification.
• CT Angiography (CTA):
  • Rapid, high-resolution 3D anatomy. Iodinated contrast.
  • Radiation. Bolus tracking.
  • For stenosis, aneurysms, dissection, trauma.
• MR Angiography (MRA):
  • No ionizing radiation. Techniques: Time-of-Flight (TOF), Contrast-Enhanced (CE-MRA).
  • Gadolinium (CE-MRA) - Nephrogenic Systemic Fibrosis (NSF) risk.
  • For stenosis, occlusion, run-off.
• Digital Subtraction Angiography (DSA):
  • Invasive gold standard; diagnostic & therapeutic.
  • Catheter-based, iodinated contrast, radiation.
  • Enables angioplasty, stenting. Risks: access site.

⭐ DSA remains the gold standard for peripheral vascular imaging, especially when intervention is planned.

Arterial Disease - Clog Combat

• Patho: Atherosclerosis is the main cause. Endothelial injury → lipid deposition → plaque → stenosis/occlusion.
• Risks: Key risks: Smoking, DM, HTN, HLD, Age, Male.
• Clinical:
  • Claudication: Exercise-induced pain, relieved by rest.
  • CLI: Chronic rest pain, ulcers, or gangrene. ABI < 0.4.
  • ALI: 📌 6 P's: Pain, Pallor, Pulselessness, Paresthesia, Paralysis, Poikilothermia.
• Imaging:
  • Doppler USG: First-line. ABI (Normal > 0.9; Claudication 0.5-0.9; CLI < 0.4). Waveform analysis: Triphasic (normal) → Biphasic → Monophasic (severe).
  • CTA: Shows anatomy, calcification, stenosis. Requires IV contrast.
  • MRA: No radiation. Gadolinium contrast (NSF risk if eGFR < 30). Non-contrast TOF MRA.
  • DSA: Gold standard, invasive. Allows therapeutic intervention.
• Findings: Common findings: Stenosis, occlusion, aneurysm (>50% normal diameter), dissection.

⭐ Leriche Syndrome: Aortoiliac occlusion. Triad: buttock/thigh claudication, absent femoral pulses, impotence.

Venous Disease - Deep Dive

• Deep Vein Thrombosis (DVT)
  • Pathophysiology: Virchow's triad (stasis, hypercoagulability, endothelial injury).
  • Imaging:
    • Doppler US (1st line): Non-compressible vein, echogenic thrombus, absent/reduced flow, loss of phasicity/augmentation.
    • CTV/MRV: For suspected iliac vein DVT or equivocal US; shows filling defects.
  • Complications: Pulmonary Embolism (PE), Post-Thrombotic Syndrome (PTS).
• Chronic Venous Insufficiency (CVI)
  • Pathophysiology: Valvular incompetence → venous hypertension.
  • Doppler US: Reflux > 0.5s (superficial veins), > 1s (deep veins).
  • Clinical: Edema, skin changes (lipodermatosclerosis, pigmentation), medial malleolar ulceration.
• Varicose Veins
  • Dilated, tortuous superficial veins.
  • Doppler US: Identifies reflux source (e.g., sapheno-femoral junction incompetence).
• May-Thurner Syndrome
  • Compression of left common iliac vein by right common iliac artery.
  • Imaging: CTV/MRV, venography.
• Superior Vena Cava (SVC) Obstruction
  • Causes: Malignancy (e.g., lung cancer, lymphoma), thrombosis.
  • Imaging: CECT shows obstruction & development of collaterals.

⭐ Phlegmasia Cerulea Dolens is a severe form of DVT characterized by sudden massive swelling, cyanosis, and pain in an extremity, potentially leading to gangrene. It involves iliofemoral DVT with near-total venous occlusion.

Other Syndromes - Pattern Pursuit

• Klippel-Trenaunay Syndrome (KTS)
  • Triad: Capillary malformation (port-wine stain), venous varicosities, limb hypertrophy.
  • Imaging: MRI, Venography. No significant AV shunting.
• Parkes Weber Syndrome (PWS)
  • KTS-like with high-flow arteriovenous (AV) fistulas; risk of cardiac failure.
  • Imaging: Doppler US, MRA, Angiography (shows AV shunts).
• May-Thurner Syndrome (MTS)
  • Left common iliac vein (LCIV) compressed by right common iliac artery (RCIA) against vertebrae.
  • Imaging: CTV, MRV, IVUS (gold standard).

  ⭐ MTS: LCIV compression by RCIA; ↑ left leg DVT risk, esp. young women.

• Nutcracker Syndrome
  • Left renal vein (LRV) compression:
    • Anterior: Between SMA & Aorta (most common).
    • Posterior: Between Aorta & Vertebral column.
  • Hematuria, flank pain. Imaging: Doppler US (↑ LRV velocity, beak sign), CTA, MRA.
• Popliteal Artery Entrapment (PAES)
  • Popliteal artery compression by gastrocnemius/band; claudication in young.
  • Imaging: Doppler US (with provocative maneuvers), MRA, CTA.

High‑Yield Points - ⚡ Biggest Takeaways

• Doppler USG is the first-line investigation for most PVDs, including DVT and PAD.
• CTA is gold standard for PAD assessment and pre-operative planning.
• MRA is valuable in contrast allergy or renal impairment as an alternative to CTA.
• DSA is the gold standard for intervention and complex diagnostic dilemmas.
• ABI <0.9 is diagnostic for PAD; a key non-imaging test.
• Non-compressibility of veins on USG confirms DVT.
• Doppler USG maps reflux in varicose veins.