Quelles sont les causes du sang dans les urines ?

Blood in urine causes

Blood in urine (pee), also called hematuria, can be a symptom of several different health conditions. These can be harmless or very serious and are usually accompanied by other symptoms.

Dr Michael Green is a reproductive health specialist and chief medical officer at Winona: "Many things can cause hematuria, but any blood in your urine is a reason to speak to your doctor."

With the help of Dr Green, we look at the most likely causes of blood in urine and explore the other symptoms of each condition. Many of these symptoms overlap, but there are some key differences, and recognising these may help you prepare for your doctors' consultation.

Infections des voies urinaires (IVU)

Infections urinaires, or UTIs, are the most common reason for finding blood in urine. Around 5 out of 10 of all women will get a UTI at some point¹, and while much less common, 2 in every 10 UTIs affect men².

UTIs are infections caused by bacteria in the bladder or urethra, the tube that urine travels down. Not everyone who gets a UTI will find that their urine has a pink or reddish stain, but bleeding is a common symptom. Dr Green explains the other symptoms that often accompany UTIs.

"Needing to pee more than usual, having a strong urge to pee, and feeling pain or a burning sensation while peeing are common to UTIs. You might experience pain or discomfort in the lower region of your stomach or your back."

Calculs rénaux

Calculs rénaux, where small and hard deposits form on the walls of your kidneys or bladder, happen in around 1 in 10 people³. Although far less common than UTIs, most people with kidney stones will find visible blood in their urine, called gross hematuria, or will have blood that doctors find with a microscope, called microscopic hematuria.

Dr Green says: "Kidney stones can sometimes move into the urinary tract, causing bleeding and pain. Unlike other causes of blood in urine, this pain is typically intense and comes and goes in waves that radiate through the lower stomach and groin."

An enlarged prostate

Men have a prostate gland just below the bladder, and this often gets bigger toward middle age. Some men experience no symptoms with an enlarged prostate, while others do. However, finding blood in urine is a rare outcome⁴. Symptoms of an enlarged prostate occur when the gland grows big enough to put pressure on the urethra, which can cause problems with peeing.

"A weak stream of urine, difficulty starting or stopping peeing, frequent peeing especially at night, and a sense that you cannot fully empty your bladder are all common to benign prostate hyperplasia - the term for an enlarged prostate that isn't cancerous," says Dr Green.

Prostate, kidney, or bladder cancer

"It's vital to rule out cancer if you experience blood in your urine, and the only way to do this is to see your doctor," says Dr Green.

Cancer de la prostate is the most common cancer for men in the UK and is diagnosed in 52,300 each year⁵. However, blood in urine is usually only a symptom if the cancer has spread to the bladder.

In the case of prostate cancer, in addition to blood in urine, symptoms can include:

• Tiredness (fatigue).

• Perte de poids inexpliquée.

• Pain in the lower back or side,

• A mass in the stomach that you can feel.

Pain is more likely to be present in the advanced stages of cancer, usually in the lower back or side.

Cancer du rein is less common, with 13,300 new UK cases each year, but blood in urine is the most common symptom⁶.

Cancer de la vessie is diagnosed in 10,300 people in the UK each year and around 8 in 10 of those diagnosed will find some blood in their urine⁷.

The doctor says: "Bladder or kidney cancer may produce less specific pain, but this pain tends to be more generalised and associated with advanced disease."

Other causes for blood in urine

The above health conditions are the main causes of blood in urine, but there are several other possibilities, and not all of them are health conditions. For example:

• Beetroot - eating a lot of this vivid red-purple vegetable might change the colour of your urine.

• Kidney or bladder injury - blood can enter your pee if you've suffered a blow to your kidneys, located just below your ribcage on each side of your spine, or your bladder in your lower stomach.

• Radiothérapie - this treatment, used for various conditions including cancer, thyroid disease, and blood disorders, can cause your bladder to become inflamed, which in turn can cause blood in urine.

• Médication - certain medicines may cause blood in urine, including the anti-cancer drug cyclophosphamide (Cytoxan), the antibiotic penicillin, medicines that prevent blood clots, and blood-thinning medicines such as heparin.

• Vigorous exercise - blood in the urine can happen after playing contact sports, such as rugby, or after long-distance sports, such as marathon running. This may be linked to bladder or kidney damage, but it's not always clear why this happens.

Pour en savoir plus

1. National Institute for Health and Care Excellence: Lower urinary tract infection in women - how common is it?

2. National Institute for Health and Care Excellence: Lower urinary tract infection in men - how common is it?

3. Nagendra et al: Hematuria as a sign of kidney stone disease evaluated using computed tomography: a review.

4. Prostate Cancer UK: Enlarged prostate.

5. Cancer research UK: What is prostate cancer?

6. Cancer research UK: Kidney cancer statistics.

7. Cancer research UK: What is bladder cancer?