Blood in horse urine: what's behind it?

What does haematuria actually look like?

Normal horse urine ranges from pale yellow to dark yellow and can be slightly cloudy due to mucoproteins. When we talk about haematuria, you'll notice a clearly pink, red, or even dark brown discolouration. Pay attention to when the blood becomes visible: at the start of the urine stream it more likely indicates a problem in the urethra or the front part of the bladder, whereas blood throughout the entire stream points to a condition higher up in the urinary tract, such as the kidneys or bladder. Record the colour, time, and frequency in your horse's EquiSight horse profile — that information is invaluable for your vet.

The most common causes at a glance

Below are the causes vets in practice most frequently encounter in horses with blood in their urine:

• Bladder infection (cystitis): bacterial infection, more common in mares due to their shorter urethra.
• Urinary tract stones (urolithiasis): mineral deposits that damage the mucous membrane; occurs in both stallions and geldings.
• Kidney infection or kidney damage: can result from infection, toxins (e.g. oak leaf poisoning) or prolonged NSAID use.
• Muscle damage (myoglobinuria): after intense exertion or in cases of azoturia the urine turns dark brown — this is not actual blood but myoglobin.
• Tumours: rare, but bladder or kidney carcinoma can occur in older horses (>15 years).
• Trauma: a fall or blow to the abdominal wall can damage the bladder or urethra.

Myoglobinuria: not the same as blood

A common mistake is confusing myoglobinuria with haematuria. In azoturia — also known as 'tying-up' — muscle cells break down and the protein myoglobin leaks into the urine. The urine then appears dark brown or coffee-brown, but contains no red blood cells. The accompanying signs are recognisable: the horse is stiff, sweats excessively, and sometimes refuses to move after exertion. Myoglobinuria is an emergency because it can damage the kidneys rapidly. Call your vet immediately and ensure the horse has access to water and rest. With EquiCoach in EquiSight you can describe symptoms and quickly get an initial assessment of the urgency.

When to call the vet immediately?

• The urine is bright red and a large amount of blood is visible.
• Your horse is showing colic symptoms alongside the discolouration.
• The horse is barely urinating or appears to be in pain when urinating.
• There is a fever (>38.5 °C) or signs of depression.
• The urine is dark brown after exertion (suspected myoglobinuria).
• Symptoms last longer than 24 hours or are getting worse.

What does the vet do during diagnosis?

The vet starts with a urine test: a dipstick gives results within three minutes on blood, protein, and pH. Microscopy reveals whether there are actually red blood cells present (haematuria) or myoglobin (myoglobinuria). Blood values such as creatinine and urea map the kidney function. If stones or a tumour are suspected, an ultrasound of the bladder and kidneys follows. On average, reaching a diagnosis takes one to three days for routine investigations; longer for complex cases. Record all observations beforehand — colour, time, diet, medication — in the horse profile, so you don't forget anything during the consultation.

Diet and management as risk factors

Diet plays a bigger role than many owners realise. An excessively high calcium content in the ration — through feeding a lot of alfalfa, for example — increases the risk of crystal formation in the bladder. Insufficient water intake is a well-known trigger for urolithiasis; in cold weather horses sometimes drink only 20–25 litres per day instead of the recommended 30–50 litres. Prolonged use of NSAIDs such as phenylbutazone can damage both the gastric mucosa and the kidneys. Use the schedule in EquiSight to track medication regimens and stop or taper off in time in consultation with your vet.

• Limit alfalfa to a maximum of 20–25% of the roughage ration in sensitive horses.
• Ensure access to clean, lukewarm drinking water in winter to encourage intake.
• Always record NSAID use in the horse profile with start and end dates.
• Have blood values checked annually in ageing horses (>12 years).