Urinalysis
Sample Requirement | Turnaround Time |
Urine | Same working day (with culture 2-3 working days) |
Urine analysis is useful to help detect renal or bladder pathology and to investigate cases of septic nephritis, cystitis or urethritis. Mid-stream samples should be collected without the use of diuretics (which alter urine composition) into a sterile universal container. Beware of owners collecting samples into other containers before pouring the urine into the provided universal container, resulting in spurious results.
Urine samples should be examined grossly for colour and consistency, the presence of blood (either fresh or changed), pus or excessive crystalline material. Horse urine is highly variable in colour from near colourless to golden or brownish and in its density, turbidity and mucinous content. Specific gravity (1.008-1.040 in adult horses, 1.001-1.025 in foals) should be measured with a refractometer. Dipsticks are commonly used to measure pH (normally 7.5-8.5 in adult horses, 5.5-8.0 in foals) and to detect other abnormalities. Urine pH reflects diet and horses grazing pasture will normally have alkaline urine whereas those on a cereal- based performance-type diet will normally have slightly acidic urine. Proteinuria may occur with inflammation or renal tubular pathology.
Glucosuria may be seen in classical Cushingoid horses and ponies.
Haematuria and sometimes haemoglobinuria may occur following traumatic injury, or with renal or cystic calculus formation. Haemoglobinuria may occur with haemolytic conditions. Myoglobinuria is seen with myopathies. Bilirubinuria may occur with choleliths or other causes of bile duct obstruction. Ketonuria is rarely seen in horses.
Microscopic examinations should be used to detect casts (protein and cellular masses), which suggest renal tubular pathology. Leucocytes indicate inflammation/infection. Bacteria which if seen following Gram stain in association with leucocytes may also indicate infection. Erythrocytes can indicate haemorrhage.
Horse urine is fundamentally a supersaturated solution of calcium carbonate and will normally contain variable amounts of predominantly calcium carbonate crystals. Urolithiasis cases usually have a degree of proteinuria and haematuria and may exhibit dysuria. Large amounts of sabulous material are not necessarily an indication of abnormality. Further investigations include bladder and kidney palpation, ultrasound scan and cystoscopic examinations, looking for sabulous (bladder) or discrete calculus formation.
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