Diagnostics
A careful examination of the horse including taking a detailed history should be carried out, i.e. some horses show respiratory disease at the same time each year e.g. COPD. The trachea and lung fields should be listened to with a stethoscope and a temperature taken. A swab can be taken of a nasal discharge, although, this can often be misleading as other bacteria may contaminate the sample or a sample taken from the back of the throat, naso-pharyngeal swab, these can then be analysed in a lab. If a sinus problem is suspected then the animal’s head should be palpated for any signs of swelling or pain and the teeth checked.
Endoscopy
This procedure involves passing a tube with a camera down the nasal passages of a horse with the image coming up instantly on a screen. This technique can be used to look at the nasal passages, larynx, areas where the sinuses drain, the guttural pouches, the trachea and bronchioles. This technique can be very useful to find masses, cysts, swellings, inflammation, assess where bleeding or discharge is coming from, visualize fluid pooling and assess how the larynx is functioning. A sample of fluid can also be taken with this technique (tracheal wash/bronchio-alveolar lavage) and then analysed in a lab to find evidence of infection, inflammation or the presence of abnormal cells. Horses may need to twitched or sedated for this procedure. In some cases, those of respiratory noise, this technique may need to carried out on a treadmill to find any abnormalities.
Radiographs (X-rays)
X-rays are produced from the x-ray machine and pass through the area you wish to image and onto a plate behind. The plate contains an x-ray film that is developed. Bone shows up white on the finished image as fewer x-rays were able to pass through it due it being thicker that the surrounding tissue. Because of this, x-rays are used mainly to assess the bones and joints and are, therefore, of limited value in assessing lung tissue in horses due to their size. X-rays are very for assessing problems of the head such as the nasal passages and sinuses and can also be used to fin areas of bleeding or tumours in the lungs. Protective clothing is worn by the people present taking the x-rays to reduce exposure and anyone under the age of 18 or pregnant must not take part in the procedure. A recent advance in x-ray technology is digital x-ray which allows the images to come straight up onto a computer screen where they can be easily manipulated.
Ultrasound scanning
Ultrasound scanning is used to look at soft tissues. The area requiring scanning must be clipped, cleansed and ultrasound gel applied. High energy sound waves are produced which hit the tissues are then rebounded back.
The way these waves return gives us the image on the screen. Unlike with most radiographic machines this image is instant.
The main problem with ultrasound scanning the lungs is that the waves don’t travel through gas, what the lungs are full of, and can, therefore, only be used to see the surface of normal lung. Ultrasound can be useful in finding abnormal lung tissue and fluid accumulations around the lungs (pleural effusion).
Bone scanning
Bone scanning detects areas of active bone remodeling ‘hot spots’ and can find problems that could not been find on radiographs or are in areas that cannot be x-rayed easily e.g. pelvis. Radioactive material is injected into the horse which binds to active bone. These areas can then be seen by a camera that picks up the gamma rays that are now being produced from the bone. After the scan horses must be quarantined for one to two days after injection due to the radioactive material. Bone scanning can be very useful in horses with sinus problems or when trauma is suspected in the head region. In sinus cases there is often the need to look into the sinus surgically using a hole in the side of the face. This can be made small to fit an endoscope through or can be made larger to improve access and allow the surgeon to easily visualize the problem.