Haematuria is defined as the presence of blood, or red blood cells, in the urine.
It may be classified as:
- macroscopic, if it is visible to the naked age.
- microscopic, it is only visible in a urine analysis (reactive strips or under a microscope).
And alternatively, according to its origin in:
- glomerular, when it originates in the kidneys. The glomeruli are a network of blood vessels that filter blood, removing excess fluid and waste through to make urine.
- non-glomerular, when it originates in the urinary system.
There are many causes of haematuria. Among them we could highlight urinary tract infections, kidney stones, tumours (kidney or bladder), traumas and associated with exercise. In this post we will focus only in the sports-related haematuria.
Sports-related haematuria is a common phenomenon, usually microscopic and transient, that appears after the exercise and mostly related to the intensity of the exercise. Only a 2-3% of haematuria cases is macroscopic.
Although the origin is not always clear, sports haematuria is usually related to a direct trauma, release of haemolysing factors, non-steroidal anti-inflammatory drug use and dehydration, among others.
In contact sports (boxing, rugby, cycling, skiing, football, hockey) traumas are frequent. In rugby for example haematuria affected 24.4% of the players. Trauma to the kidneys is the most frequent one (75-80% of urological traumas), followed by urethral and bladder injuries.
In non-contact sports (swimming, rowing or running) haematuria is mainly caused by physiological changes during the effort. Catecholamines are secreted by exercise to divert blood from the kidneys to the muscles. This may cause hypoxic damage to the kidneys and increase the permeability of glomeruli, releasing red cells to the filtrated urine.
As mentioned previously, among the factors contributing to haematuria exercise intensity is key: significantly higher levels of haematuria were found in athletes sprinting at high intensity over others running at lower intensity or simply cycling.
If haematuria persists for longer than 48 h, especially if it is visible and despite sport effort, medical advice should be seeked. Usually a computed tomography scan is prescribed to discard any underlying condition, usually urinary tract abnormalities.
Keep healthy and look always for medical advice if you find any sign of blood in your urine.
Haematuria in Sport: A Review.
Akiboye RD, Sharma DM.
Eur Urol Focus. 2019;5(5):912‐916. doi:10.1016/j.euf.2018.02.008