Diagnostic techniques for the equine

Diagnostic Techniques for the Equine

What is a diagnostic technique?

▪ A diagnostic technique is a procedure

followed in making a medical diagnosis

Recent advances

The new imaging techniques can replace the physical examination

But each technique may provide additional information

Improved diagnostic capabilities allow earlier surgical intervention

when necessary

This in turn improves survival rates and economic aspects

Non-invasive Diagnostic Procedures

Non-invasive equine diagnostic techniques

include: Thermography Ultrasound MRI – Magnetic Resonance Imaging X-ray CT Scan

Invasive Diagnostic Procedures

Endoscopy

Gastroscopy

Nerve Blocking (subcutaneous, intra-articular including

spine and sacroiliac joint)

Nuclear Scintigraphy

Arthroscopy

Thermography

Infra red rays are given off by body heat and can be recorded

and a picture produced (thermograph)

Inflamed areas are warmer than normal and will show up in

colour on the screen of thermogram

Can pinpoint sites of trauma that cannot be clinically diagnosed

or isolated by nerve blocks

Thermography

Ultrasound

Used for examining soft tissue, particularly tendons and ligaments, but also many

other structures including joints and even eyes.

Sound waves leave the transducer and enter the body, where they reflect off the

bone and soft tissue to produce an echo that is analysed by a computer in the

ultrasound machine and transformed into moving pictures of the organ or tissue

that is being examined.

Bone, which is dense, is identified on screen as a bright line, whereas

a tendon appears as a dotted pattern.

Ultrasound

Ultrasound images are real-time, so unlike X-rays, where you can

only see a static image, with ultrasound movement can be seen

Ultrasound cannot be used

to examine the deeper structures

in bone as bone matter is too dense

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Ultrasound

Ultrasound can also be used to view bone surfaces

Looking for the presence of fractures and infected bone

During assessments detailed measurements are taken

Then during the rehabilitation period the degree of healing can be

assessed

Comparing the initial measurements to the current scan at each recheck

MRI – Magnetic Resonance Imaging

Uses powerful magnetic field instead of radiation to create images

No lead aprons are required

Images are in black and white take only a couple of minutes to generate

Images can be viewed dorsally (top of horse)

Transversely (horizontal cross section)

Sagittally (Vertical cross section)


How it works-

The body is composed mainly of water, so there are loads of hydrogen protons

These protons behave like tiny magnets each with their own magnetic field

Body part being examined is placed in the centre of a strong magnetic field

This causes the hydrogen protons to align


Radio waves are fired into the area

The protons release energy in the form of radio waves which are detected by a receiver coil

Can expose all internal structures together

That is tendons, ligaments, bone etc

Get a whole picture

Best for foot lameness and evaluating fetlock, upper cannon region, knee, hock and the

horses head


MRI is expensive

Is only used when diagnosis cannot be reached using

standard imaging techniques – radiography and

ultrasound


X-Ray – Digital Radiography

There are two forms:

Computerised

Direct capture

Both result in the production of an image on a computer screen

X-rays are acquired using a conventional x-ray machine they use special imaging

plates

With computed radiography a machine called a reader extracts information from the

imaging plate


The image is displayed as a digital image on a

computer screen

Currently on large sized imaging plates are only

available

Therefore direct digital radiography is limited to use on

limbs


Possible for vets to send electronically images for a second opinion

A proper investigation will require a minimum of four images per joint

Direct digital radiography is quicker than computerised radiography

But capital costs of equipment are greater

Computer for direct digital radiography is linked by cable to the detection plate

– risk of equipment damage


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CT Scan – Computed Tomography

An imaging technique that uses a rotating x-ray machine and a

computer to create cross-sectional slices through the body

Generates multiple images of the body

Only available in a small number of veterinary hospitals in the UK

The CT scanner is particularly useful for investigating and diagnosing

dental diseases as well as conditions affecting the sinuses, brain and

skull also taking images of the lower leg.


Images are clearer than the traditional x-ray machine allowing more

accurate diagnosis

Only the head can be scanned whilst horse is standing

In order to scan a standing animal, the horse is sedated and stands on a

moving platform that moves the head through the doughnut-shaped

scanner

All other areas to be scanned require general anaesthetic


Bone is shown in great detail but MRI is better at

visualising soft tissue


Endoscopy

One of the most important special diagnostic tool

Been used by equine practitioners since 1970

It is a flexible telescope with an attached video camera

This is used to visualise internal organ systems while the horse

is sedated

Endoscopy

Widely employed to investigate the respiratory system of

the horse

This is where functional disorders frequently occur in the

upper airway

Gastroscopy involves passing the endoscope down the

esophagus to the stomach.

Reasons to use Endoscopy

Choking up or tongue swallowing or dorsal displacement of

the soft palate (DDSP) Most commonly in race horses

Thought to be related to a disruption in the anatomical relationship between

larynx and soft palate

Exercise induced pulmonary haemorrhage

(EIPH) Occurs in the lungs as a consequence of moderate to strenuous exercise

Related to mechanical stress in the lungs which occurs with forceful breathing

Dynamic Endoscopy

Dynamic endoscopy allows the clinician to examine the upper airway of the horse whilst it is

exercising

Dynamic obstructions of the equine upper respiratory tract may be undiagnosed when resting

endoscopic examination is performed

Two methods to examine upper airways during exercise

Treadmill

Overground endoscopy

Dynamic endoscopy on a high speed treadmill provides a far better assessment

Treadmill endoscopy is available in limited facilities

Dynamic Endoscopy

Overground endoscopy are able to carry out

assessments repeatedly from one day to another

without delay and transportation to treadmill centre

Its safer for both horse and personnel

Should be performed with an experienced rider

Dynamic endoscopy

Overground Endoscopy

Treadmill Endoscopy

Nerve Blocking Nerve and joint blocks involve the injection of a local anaesthetic either close to a nerve or directly into

a joint or into another synovial cavity.

These blocks are used as one part of an examination of the lame horse used to isolate a source of

pain

The local anaesthetic temporarily disrupts the function of any nerves or nerve endings it contacts. This

results in areas of desensitisation (numbing). The desensitised area depends on which nerves or

nerve endings are affected

Typically the blocks are started at the lowest points, working up the limb to isolate the area of pain

Nerve Blocking


Involves injecting a horse with radioactive dye

Usually a substance called technetium

It’s this that shows up on the scan

Maker can be linked to a number of different tissue

seeking molecules


Technetium – MDP is attracted to bone

Normal bone has a slow replacement rate

But areas of damage and disease will have an

increased rate of turnover

Will show up as hot spots and red areas on a scan


Can image areas such as back, pelvis and head areas

A sensitive method of demonstrating bone injuries in horses e.g. Stress

fractures

Does not give any information on cartilage, ligaments or tendons

Strict radiation protection must be followed

Equine patient must be isolated after having scintigraphy performed


Arthroscopy

Is routine procedure in human medicine – keyhole surgery

The keyhole technique by which surgery is performed on equine joints for

traumatic injury, fractures within joints, soft tissue injury, and abnormal joint

development in young horses, such as osteochondritis dissecans (OCD).

A small telescope can be inserted into the joint

Powerful source of light is transmitted down the arthroscope

Allows visualisation of joint interior

Arthroscopy

Small instruments are then inserted into the distended joint

There are a variety of attachments – usually between 2 – 4.5 mm in diameter

Capable of removing areas of damaged cartilage, membrane and bone

Arthroscopy

Education

Diagnostic techniques for the equine