Haematuria is the medical term for passing blood in the urine. Several different conditions and diseases can cause haematuria. Although most causes are benign, it can be a sign of a significant health problem, even if it happens only once, so you should talk to your GP as soon as possible.
If the cause for the blood in the urine is not apparent, then your doctor may want to refer you for further tests. This usually involves a CT scan of the urinary tract and an endoscopic examination of the bladder (cystoscopy).