Ultrasound

Introduction

• This page is meant to present summary notes on ultrasound that are meant for teaching purpuses.
• Actual images and demonstrations for learners can be found on impocus.ca made by Dr. Barry Chan

Lung Parenchyma

• General Principles
  • Use Linear / Curvilinear / Phased array
  • Probe must be PERPENDICULAR to pleura (otherwise, artifact will be incorrect)
• 5 Basic Signs:
  • A-Lines
    • What are they?
      • Curved arcs inferior to pleural line
      • Mirror images of pleural line = represent artifact (do not exist).
      • Distance between pleural and 1st A-line = distance between all A-lines
      • Continue to appear regardless of depth
    • A-lines mean: "Air in thorax"
      • Normal Lung
        OR
      • Pneumothorax
  • B-Lines ("aka Comet Tails)

    

    • "Laser-like vertical reverberation artifacts arising from the pleural   (not above or below)   line, extend to bottom of screen without fading + move synchronously with respiration"
      • Beam travels between probe and pleural line (reflects from interlobular septa) and travels back (forming a second line), each round-trip = next line.
    • Meaning:
      • ≥3 = "interstitial syndrome"

    • Focal B-lines	Bilateral B-line
      Pneumonia Contusion Infarction Pleural Disease Neoplasia Atelectasis	Pulmonary Edema Interstitial Pneumonia Interstitial Pneumonitis Pulmonary Fibrosis

    • Causes: CHF
    • More B-lines = more severe
      • "Search Light Sign" = multiple B-lines overlapping = severe interstitial syndrome (severe pulmonary edema, severe ILD)
  • Hepatization
    • Greyish-appearing lung that penetrates U/S beams with ease making the lung look like the liver. 
    • Meaning: Air devoid alveoli
      • Brighter (echoic) = less severe ("incomplete hepatization")
      • Grey (hypoechoic) = more severe ("complete hepatization") 
    • Causes:
      • Atelectasis, etc..
  • Air Bronchograms
    • Meaning: Air devoid lung (alveoli) that surrounds air-filled airways
    • Two types:
      • Dynamic = moves with respiration = air in bronchi that moves with breathing
        • Means: bronchus is patent
      • Adynamic = bronchus (often punctiform, echoic, dot lung parenchyma), do not move with patient breathes
        • Means: bronchus is NOT patent 
      • No air bronchograms = resorbtive atelectasis (i.e. 100% bronchus obstruction), no air in bronchus. (esp if hepatized lung)
  • Fractal (Shred) Sign
    • Coarse, irregular, discontinued line.  Separates more and less consolidated areas
      • B-lines can arise from the line (pleural line may not be seen)
    • Cause: Subsegmental Consolidation
    • Meaning: presents interface between consolidated and aerated lung
      • Represents part of the lung has alveolar consolidation

Renal Ultrasound

• Below is simply a review summary, please see video for details: http://medref.ca/impocus/renalultrasound/

• Introduction
  • Probe: Use curvilinear probe or phaser probe
  • Position: Supine or Slight Lateral Decubitus
  • Start: Posterior axillary line intersection with subcostal margin
    • Keep marker towards head (cranial)
    • Scan the kidney up/down left/right to see entire organ.
  • Views:
    • Longitudinal
    • Axial
  • Retroperitoneal organs, so hard to see
    • Left kidney: harder to see
    • Can use liver + spleen used to shoot through (as acoustic windows)

• Anatomy
  • (RIght) Normal Kidney Longitudinal View
    • Identify:
      • Renal Capsule
      • Renal Cortext (slightly hypoechoic)
      • Renal Sinus (Medulla, Calices, Pyramids)
    • Axial View is similar
• Pathology
  • Hydronephrosis
    • Main question: Does this person have hydronephrosis?
      • Can grade hydronephrosis by apperance (as mild/mod/severe)
      • 
      • There is a grading system, but it's not important for POCUS.

        Grade	Description
        Grade I	Slight blunting of calyceal fornices
        Grade II	Blunting and enlargement of calyceal fornices but easily seen shadows of papillae
        Grade III	Rounding of calices with obliteration of papillae
        Grade IV	Extreme calyceal ballooning

• Cautions:

  • DO NOT: Compare degree of hydronephrosis to previous (radiology skill - obtain official radiology U/S)