Ultrasound

It has been recommended that my dog have an ultrasound. What does this involve?

Ultrasound examinations (also known as ultrasonography or echosonography) are  imaging techniques in which deep structures of the body can be visualised by recording echoes of ultrasonic waves which are directed into the tissues. Unlike X-rays which are potentially dangerous, ultrasound waves are considered to be entirely safe.

The principal involves directing a narrow beam of high frequency sound waves that may be transmitted through, reflected by or absorbed by the tissue toward which they are pointed, depending on the nature of the surface they strike.

As the beam strikes the interface or boundary between two tissues, some are absorbed and others are reflected back to the transducer which originally generated them. These reflected sound waves are then converted into electrical impulses which are displayed on a screen. This is a 'picture' of the tissues under examination.

The technique is invaluable for the examination of internal organs and was first used in veterinary medicine for pregnancy diagnosis. However the technique is also extremely useful in evaluating heart conditions and also in identifying size and changes in organs in the abdomen. It is therefore very useful in the diagnosis of cysts and cancers.

Does the technique have any drawbacks?

Ultrasound examinations are of little value in the examination of organs that contain air. Ultrasound waves will not pass through air and therefore it cannot be used to examine the lungs.

Are there different forms of ultrasound?

Depending on the images produced, ultrasound can take various forms. In veterinary work B-mode ultrasound is the most usual. This gives a two dimensional picture of the organ scanned. M-mode is also used. This is a type of B-mode in which the tracing of the motion of the object scanned is displayed. This is used mainly for the evaluation of heart function.

Doppler ultrasound is a further advance in which measurement and a visual record are made of flow velocity in the vessels being scanned and again is useful in cardiology.

Are ultrasound scans available for evaluation of my dog’s heart problem?

Yes, many clinics are becoming equipped with sophisticated ultrasound equipment that can undertake b-mode, M-mode and Doppler scans. Images can be frozen and then printed from the computer to provide a positive record of the examination. In some cases however, it may be recommended that referral to a cardiologist or a specialist ultrasonographer is preferable.

Will my dog have to have an anaesthetic?

Anaesthesia is usually unnecessary. This is the great advantage of ultrasound. The technique is non-invasive but does involve clipping an area of hair and applying a water soluble jelly so that good contact can be made between the transducer and the skin. The technique is totally painless and most animals will lie quite comfortably while the scan is being carried out. Occasionally, if very frightened or fractious a sedative may be necessary.