Urinary blood (haematuria) refers to the presence of red blood cells or haemoglobin in the urine. Normally, the kidneys' filtration membranes prevent red blood cells from entering the urine. When blood is detected, it indicates disruption of this filtration barrier or bleeding somewhere in the urinary tract.
Common causes include urinary tract infections, kidney stones, glomerulonephritis, bladder polyps or cancer, trauma, vigorous exercise, and — in women — menstrual contamination. Microscopic haematuria (detected only on testing) is more common than macroscopic haematuria (visible blood in urine). Any persistent haematuria requires further investigation to identify the source.
FAQs
Is dipstick blood the same as haematuria?
Not always. Dipstick reacts with haemoglobin from haemolysis or myoglobinuria, causing false positives. Microscopy confirming red blood cells is needed for true haematuria.
What are dysmorphic red cells?
Red cells deformed by passage through the glomerular filter, indicating glomerulonephritis rather than lower urinary tract bleeding.
Does all haematuria need investigation?
Yes. Persistent haematuria in adults over 40 warrants investigation to exclude bladder cancer. Single episodes in young women are more often from UTI or menstrual contamination.
Can exercise cause blood in urine?
Yes. Vigorous running can cause transient runner's haematuria from bladder trauma. It resolves within 24-48 hours.
