ULTRASOUND OF PLEURA (A MANUAL)

Indications –

Ultrasound can detect pleural fluid and may be helpful in localizing small pleural effusions when aspiration is indicated or skiagram is doubtful for pleural effusion.If X-ray is already available confirming the pleural fluid, the only reason to use ultrasound is to guide aspiration when the fluid is loculated or there is only a small amount.

(Message – it is not necessary to use ultrasound to aspirate every effusion)

Preparation – 1. Preparation of the patient – No preparation is required.2. Position of patient – Whenever possible, the patient should be

scanned while sitting comfortably. Apply coupling agent (Ultrasound Gelly) liberally over the lower part of the chest on the side to be scanned.

3. Choice of transducer – Use a 3.5MHz frequency transducer. Use a 5MHz transducer for children or thin adults. Choose the smallest transducer available in order to scan between the ribs. If only a large transducer is available, there will be shadowing from the ribs, but information can still be obtained.

4. Setting the correct gain – Adjust the gain to obtain the best image.

Scanning Technique – The transducer should be centered between the ribs and held perpendicular to the skin. Echo-free pleural fluid can be recognized above the diaphragm, lying in the pleural space. The lung will be highly echogenic because of the contained air.

First scan the suspected area and compare with X-ray if available; then scan at different levels because the effusion may be loculated and is not always in lower pleural space (the costophrenic angle). Alter the patient’s position to see how much the fluid moves.

Normal Lung-The air filled lung surface totally reflects the ultrasound beam and produces a bright, echogenic line of sound reflection. Although transmission of ultrasound beam deeper into chest is blocked, the ultrasound image displays a characteristic pattern of bright echoes produced by reverberation artifact. The Abnormal pleura & Pleural effusion- The parietal pleura is located about 1 cm deep to rib surface. Pleural fluid is visualized as the anechoic space (black) between the parietal pleura and highly reflective visceral pleura lung interface. Pleural effusions are

hypoechogenic or slightly echogenic, and sometimes contain thick septa. Liquid, blood and pus is also echo free, but septations may cause reflections. It is not always possible to differentiate between fluid and solid pleural or peripheral masses. Move the patient to different position and rescan. Fluid will usually move unless there is loculation or an excessive amount. Peripheral lung or pleural masses do not move. Aspiration may be the way to establish the diagnosis. Anechoic fluid may be either transudate or exudate. However, fluid that contains echogenic particulate matter or thin fibrin septations or that is associated with thickened pleura or pleural nodule is virtually always an exudate.

Sonographic signs of pleural effusion-1. Anechoic to homogenously hypoechoic space between visceral and

parietal pleura. 2. Floating echodensities.3. Moving septations.4. Shape corresponding to pleural space.5. Lung movement within fluid.6. Anechoic or hypoechoic fluid above diaphragm.

Sonographic signs of pneumonic consolidation –1. Homogenous hypoechoic lung.2. Wedge shape.3. Well defined peripherally by visceral pleura.4. Ill defined centrally.5. Sonographic air bronchogram.6. Sonographic fluid bronchogram.7. Appropriate motion with respiration.

Sonographic signs of pulmonary atelectasis – 1. Wedge shaped echogenic lung tissue.2. Volume loss.3. Crowding of fluid filled bronchi/vessels.4. Sonographic fluid bronchogram.5. No Sonographic air bronchogram.6. Appropriate motion with respiration.