Inferior Vena Cava and Iliac Veins

Objectives

  • Anatomy and physiology of inferior vena cava (IVC) and iliac veins.
  • Patient and sonographer positions for ultrasound exams.
  • Maneuvers to improve ergonomics and imaging quality.
  • Required images for ultrasound of IVC and iliac veins.
  • Common pathologic conditions and anatomic variants of IVC and iliac veins.
  • Complementary roles of color, spectral, and power Doppler evaluations.
  • Characteristics of grayscale, color, and spectral Doppler in pathologic conditions.

Anatomy

  • External Iliac Veins: Drain lower extremities, start at inguinal ligament.
  • Internal Iliac Veins: Drain pelvic viscera, join external iliac veins.
  • Common Iliac Veins: Formed by external and internal iliac veins; terminate to form IVC.
  • Inferior Vena Cava (IVC): Begins at 5th lumbar vertebra, lies retroperitoneal on right of abdominal aorta, ends at right atrium. Diameter: (17−20extmm)(17-20 ext{ mm}) in well-hydrated patients.

Anatomic Variants

  • Paired vena cava, left-sided IVC, absence of intrahepatic portion, and membranous obstruction.

Patient Preparation

  • Fast for 8 hours to reduce bowel gas.
  • Positioning: Begin supine, adjust bed height, apply gentle pressure with probe for better vessel visualization.

Scanning Technique

  • Use low-frequency transducer (2-5 MHz).
  • Capture longitudinal and transverse images of IVC from xiphoid process to distal IVC.
  • Coronal plane imaging useful for distal IVC and iliac confluence; reverse Trendelenburg may assist imaging iliac veins.
  • Follow iliac veins systematically from confluence through pelvis.

Diagnosis

  • Normal IVC/Iliac Veins: Echogenic walls, anechoic lumen; diameter changes with respiration.
  • Thrombosis: Distended vein with echogenic material; free-floating material may also be present.
  • Neoplastic Obstruction: Echogenic intraluminal tumor, dilated collateral veins likely.
  • IVC Interruption: Device to trap thromboemboli; visualize with ultrasound.

Doppler Characteristics

  • Color and Power Doppler: Assess for thrombus, IVC filter placement, and vascular connections.
  • Spectral Doppler: Normal flow should be respiratory phasic; loss of phasicity indicates obstruction; valuable for iliac vein evaluation.

Duplex Ultrasound Guidance for IVC Filter Placement

  • Procedure traditionally through angiography; ultrasound allows bedside placement without radiation.
  • Identify right renal artery as landmark.
  • Confirm filter expansion and placement during procedure with real-time imaging.

Intravascular Ultrasound (IVUS)

  • Provides real-time imaging during endovascular procedures; detects wall thickening, webs, and nonocclusive thrombus.