Section: Diagnosis In-depth
Respiratory Disorders
Endoscopy of the upper airways reveals laryngeal paralysis and may show signs of bleeding due to EIPH or excessive mucous due to IAD. In order to determine if the laryngeal paralysis is actually impeding performance, it may be necessary to carry out endoscopy while the horse is working on a treadmill.
Lung function testing or bronchoalveolar lavage (lung wash) is imperative in the detection and treatment of IAD. Lung function testing reveals if there is small airway blockage and how severe it is. Bronchoalveolar lavage will demonstrate the composition of inflammatory cells in horses with IAD, and red blood cells or their break-down products in the horse with EIPH.
X-rays of the chest may show areas indicating inflammation and thickened lung tissue in horses with IAD and EIPH.
Musculoskeletal Disorders
Nerve and joint blocks to narrow down the exact site of lameness
X-rays of suspected sites of lameness to determine if there is evidence of DJD
Ultrasound of tendons, ligaments, and joints to determine if there are any structural abnormalities involving these joints
Nuclear scintigraphy to diagnose DJD and navicular disease when specific lesions do not show up on X-rays and to diagnose RER
Specific blood chemistry tests to diagnose RER. In particular, creatine phosphokinase (CPK), an enzyme that leaks from damaged muscle cells, is elevated in horses with RER.
Urinalysis to detect evidence of damaged muscle cells in horses with RER. The most common finding is a discolored, brown-red urine that contains byproducts of muscle breakdown such as myoglobin.
Muscle biopsy to determine the extent of damage that has been caused by recurrent bouts of RER – the only way to definitively diagnose PSSM
For Neurological Disorders
X-rays of the neck may show areas of narrowing or damage due to unstable vertebrae. Often, it is necessary to perform a contrast study, called a myelogram, in order to determine if there is any compression of the spinal cord.
Cerebrospinal fluid (CSF) tap is the best way to diagnose EPM. Horses who are positive to testing for S. neurona are more likely to actually have the disease. Blood testing alone will only tell you if your horse has been exposed to the disease (in many areas, over 50 percent of horses have been exposed to S. neurona without developing neurologic disease). However, even the CSF test is fraught with many interpretation dilemmas.
Cardiovascular Disorders
An ECG (electrocardiogram) shows the characteristic super irregular rhythm of atrial fibrillation.
An echocardiogram is often recommended to determine if there is any underlying cardiac disease in horses with atrial fibrillation.
A treadmill stress test with an ECG and echocardiogram may be useful to determine the extent to which the cardiovascular system is contributing to poor performance.
A stress test can be performed in some institutions to see if a heart problem is affecting performance.
Gastrointestinal Disorders
Gastroscopy (endoscopic examination of the stomach) reveals areas of reddening and erosion in the otherwise smooth, glistening surface of the stomach.
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