Definition
Exercise-induced haematuria refers to the presence of blood in the urine after intense physical activity. It can occur after a running session, a marathon or prolonged exercise, particularly in distance runners. The term haematuria literally means the presence of red blood cells in the urine; there are two forms: macroscopic haematuria, where the urine turns red or dark, and microscopic haematuria, where the blood is only detectable on urine testing. In runners, this usually appears in the hours following intense or prolonged exercise.
Finding red or brownish urine can be alarming for an athlete. In most cases, exercise-induced haematuria is benign and transient, but it sometimes requires medical advice to rule out a urological or kidney cause.
Anatomy
Several mechanisms can explain exercise-induced haematuria. During running, repeated impacts can cause microtrauma to the bladder wall: when the bladder is almost empty, its walls can come into contact and cause small lesions responsible for transient bleeding. The repeated jolts caused by the foot striking the ground can also irritate the urinary system, a phenomenon seen particularly in long-distance runners.
During intense exercise, part of the blood flow is also redirected to the working muscles: this reduction in renal blood flow can temporarily disrupt kidney filtration and promote the passage of red blood cells into the urine.
Epidemiology
Exercise-induced haematuria is seen particularly in distance runners. Marathon runners are more affected than other runners, because the prolonged effort and repeated impacts of long-distance running promote this phenomenon; sports involving many impacts (running, combat sports, team sports) are overall the most affected.
Causes & risk factors
Certain factors increase the likelihood of exercise-induced haematuria: long-distance running (marathon, trail), repeated impacts on hard surfaces, dehydration, an empty bladder during exercise, or high training intensity.
Symptoms
Exercise-induced haematuria can show up as pink, red or brownish urine, with the discolouration appearing after training and gradually disappearing within 24 to 72 hours. In most cases, there is no associated pain. If the discolouration persists for several days, a medical check-up is recommended.
Further tests
Urine test
The first test carried out by the doctor if episodes persist or recur, in order to confirm the haematuria and guide further investigations.
Kidney or bladder ultrasound
Helps to rule out a urinary tract infection, a stone or kidney disease as the cause of the bleeding.
Further tests
May be requested if necessary, depending on the clinical picture and initial results.
Differential diagnoses
Urinary tract infection
Usually accompanied by fever or burning on urination, unlike benign exercise-induced haematuria, which is most often painless and transient.
Urinary stone
Suspected when there is associated lower back or abdominal pain; to be looked for with ultrasound if in doubt.
Kidney disease
To be ruled out if the haematuria persists for several days or if episodes recur after training.
Treatment
Monitoring an isolated episode
In most cases, no specific treatment is needed: exercise-induced haematuria clears up spontaneously within 24 to 72 hours. If the episode is isolated and clears up quickly, returning to sport is generally possible.
When to see a doctor
Even though exercise-induced haematuria is often benign, certain situations should prompt a consultation: blood in the urine for several days, lower back or abdominal pain, fever or burning on urination, or repeated episodes after training. The doctor may then carry out a urine test, a kidney or bladder ultrasound, and further tests if necessary, in order to rule out a urinary tract infection, a stone or kidney disease.
Prevention
Stay well hydrated
Adequate hydration helps to limit bladder irritation and to promote urinary elimination.
Adapt your training
Long distances or very intense training increase mechanical stress; increasing training volume gradually reduces this risk.
Frequently asked questions
Is it serious to pass blood in the urine after a run?
Can I keep running?
Are marathon runners more affected?
Key points — Institut Basque du Coureur
Exercise-induced haematuria is the temporary presence of blood in the urine after intense physical activity. In runners, it is most often benign and clears up on its own within 24 to 72 hours. Good hydration and a sensible progression in training help limit it; persistence beyond a few days, associated pain, fever or repeated episodes should prompt a medical consultation.
Similar injuries
Exertional heat stroke in runners
A medical emergency in which body temperature exceeds 40°C, with failure of thermoregulation during exercise in hot conditions.
Hyponatraemia in marathon runners
Excessive dilution of blood sodium caused by overhydration during long races, which can lead to serious neurological problems.
Overtraining in runners
An imbalance between training load and recovery, causing persistent fatigue, reduced performance and an increased risk of injury in runners.