Ultrasound

Ultrasound is used in medicine as a diagnostic tool to evaluate organs under the skin. Ultrasound is sound of a higher frequency than that which is heard by the human ear. It consists simply of bursts of sound that are pulsed into the body by a probe. The probe listens for the returning echoes which are then converted by a computer or ultrasound machine into a picture which can be interpreted by the radiologist. Most people are familiar with its use in ladies for pregnancy where the doctor is looking at the fetus in the womb.

Diagnostic ultrasound or ultrasonography has been used roughly since the late 1940s and early 1950s when technology used to develop sonar during World War II was further refined for medical applications. Its use however did not become mainstream until the 1970s. Today, is a commonly used imaging technique in both human and veterinary medicine together with x-rays, computed tomography (CT) and magnetic resonance imaging (MRI).

Ultrasound was particularly good at looking at areas of soft tissue or fluid such as the abdomen, the heart, muscle and tendons for example. It is much less good at looking through areas of gas or bone and so, with some notable exceptions, it is of less use in investigations of the lung or skeleton for example.

As technology has improved and the cost of equipment decreased, ultrasound has become much more available in veterinary medicine. The interpretation of the images however is very dependent upon the experience of the operator. Ultrasound is a painless examination and has the advantage of being able to be used in awake dogs and cats without the necessity of sedation or anaesthesia. The hair on the area to be examined needs to be clipped so that a conducting jelly can be applied directly to the skin to produce the best image quality. Just as with babies in the womb, it can see into areas of soft tissue and fluid much more clearly than x-rays for example.

Ultrasound is used commonly to investigate abdominal pain or swelling or lumps and bumps. It is used commonly in the investigation of cancer for example and assessing where it may have spread. If necessary, the doctor or vet can visualise a needle on the ultrasound screen and guide it into an abnormal area under ultrasound guidance to take a biopsy.

Other common examples of its use in the abdomen would be in the investigation of vomiting, diarrhoea, pain or straining when urinating or defecating, blood in the urine or faeces, increased frequency of drinking or urinating, poor appetite, unexplained weight loss or incontinence.
Computed tomography (CT) and magnetic resonance imaging (MRI) are also very useful in investigation of abdominal disease. There use in this regard however is currently limited due mainly to reasons of cost and availability.

Ultrasound can also be used to evaluate muscle, ligaments and tendons as well as some joints including the shoulder and stifle. The periosteal surface of bone can be imaged clearly although the deeper bone will not be seen. Increasingly however, magnetic resonance imaging (MRI) is being used in the investigation of joints, their surrounding soft tissues and underlying bone.

Ultrasound of the heart or echocardiography is now a very commonly performed procedure in veterinary medicine. This has the advantage over x-rays of being able to visualise each of the individual chambers of the heart and in particular see the heart moving in real-time. The valves in the heart may also be visualised and their structure and function evaluated. The location of heart murmurs may be pinpointed and their potential clinical significance assessed. This is most commonly done with the dog or cat lying on their side on a especially constructed table with a cutout such that the examination can be performed from underneath.  Once again, the patient may be held gently but firmly by an assistant and sedation is usually not required.

Using echocardiography we are now more able to differentiate between different causes of heart disease such as acquired mitral valve thickening, dilated or hypertrophic cardiomyopathy and congenital lesions such as pulmonic or aortic stenosis, atrial (ASD) or ventricular (VSD) septal defects, patent ductus arteriosus (PDA), Tetralogy of Fallot and congenital mitral or tricuspid dysplasia.

All in all, ultrasound has been a tremendous boon to veterinary as well as human medicine and many disorders can now be diagnosed without the use of invasive or surgical procedures.