What is blood in urine?
Blood in the urine (known medically as haematuria) can be an indication that the kidneys aren’t working properly.
It can be caused by a variety of issues, some of them serious, so make an appointment to see your GP if you think you may have blood in your urine.
What does blood in urine look like?
Urine can appear pink, red or even dark brown, like the colour of weak black tea. Sometimes there may only be microscopic quantities of blood, so doctors often use a simple dipstick test (using a sample of urine) to confirm if blood is present.
Causes of blood in urine
There are many possible causes for blood in urine including:
Urinary infection (cystitis)
This is by far the most common cause of haematuria, particularly in young women. It can also be referred to as a urinary tract infection (or UTI). If blood in urine coincides with symptoms of cystitis and disappears a few days after the infection is treated by your GP, no further tests are usually carried out. The other symptoms of cystitis are:
- burning feeling on passing water
- feeling the need to pass urine more often
- feeling that the bladder has not been emptied
- sometimes a fever and feeling unwell.
Bleeding may occur when a kidney stone is being passed. This can often be accompanied by an attack of severe pain from the loins (the sides between your lower ribs and pelvis), across the abdomen and into the groin.
Large stones inside the kidney may also cause very slight bleeding. This can usually only be detected by the dipstick test.
Tumours in the bladder or kidney
Bladder and kidney tumours tend to become more common with increasing age, so haematuria in anyone over 40 requires further investigation.
Glomerulonephritis is a general term for several conditions involving damage to the kidney filters. It is the most common cause of blood in the urine of children and young adults, but it can occur at any age.
Polycystic kidney disease
Polycystic kidney disease (PKD) is an inherited disorder which is present from birth but seldom causes symptoms before adult life. Blood in the urine, sometimes accompanied by pain in the loin, is often the first symptom of the illness.
Blood clotting abnormalities (e.g. haemophilia, or Warfarin treatment) can cause haematuria, but the haematuria shouldn’t be put down to the blood clotting problem without a check for other causes.
Sickle cell disease
Haematuria can eventually become a feature of sickle cell disease, an inherited condition which mainly affects people from African and Afro Caribbean backgrounds and is usually diagnosed in childhood.
Alport’s disease and thin basement membrane nephropathy
These are diseases in which genetic mutations in genes for a particular type of collagen disrupt the structure of the kidney filters, making it easier for red blood cells to leak through the filters. Some forms are benign, but others can progress. At present, a kidney biopsy (a medical procedure in which a small sample of kidney tissue is taken with a needle and then examined under a microscope) is often necessary to make an accurate diagnosis,
Diseases of the prostate gland may also cause haematuria in men.
You may get blood in your urine if you injure your kidneys (e.g. if you are involved in an accident).
Some blood diseases can cause the blood pigment haemoglobin to leak into the urine and turn it red or reddish-brown. This is known as haemoglobinuria. It can also arise as a complication of having an artificial heart valve and can even be brought on by prolonged running on hard surfaces.
Harmless causes of red urine
Urine can also change colour due to:
- Menstruation – as menstrual blood is discharged at the same time as urine.
- Food colourings – foods (such as beetroot) and some food dyes can turn urine red.
Resources for you
Why we need more research
More accurate ways of telling whether blood in the urine is coming from the kidney filters, from tumours, or from kidney stones would be very helpful.
Meanwhile, we are funding numerous studies into many of the diseases which cause haemuturia, including Alport syndrome. Professor Rachel Lennon’s work in this area has gone from strength to strength. Her team are using cutting edge techniques to get to grips with the early stages of disease.
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