What is blood in urine (hematuria)?
Hematuria, or blood in the urine, can be either gross (visible) or microscopic (blood cells only visible through a microscope). Gross hematuria can vary widely in appearance, from light pink to deep red with clots. Although the amount of blood in the urine may be different, the types of conditions that can cause the problem are the same, and require the same kind of workup or evaluation.
People with gross hematuria will visit their doctor with this as a primary complaint. People who have microscopic hematuria, on the other hand, will be unaware of a problem and their condition will most commonly be detected as part of a periodic checkup by a primary-care physician.
What are the causes of blood in urine?
The causes of gross and microscopic hematuria are similar and may result from bleeding anywhere along the urinary tract. One cannot readily distinguish between blood originating in the kidneys, ureters (the tubes that transport urine from the kidneys to the bladder), bladder, or urethra. Any degree of blood in the urine should be fully evaluated by a physician, even if it resolves spontaneously.
Infection of the urine, (often called a urinary tract infection or UTI) stemming either from the kidneys or bladder, is a common cause of microscopic hematuria. Urine is naturally sterile and should not contain bacteria. Kidney and bladder stones can cause irritation and abrasion of the urinary tract, leading to microscopic or gross hematuria. Trauma affecting any of the components of the urinary tract or the prostate can lead to bloody urine. Hematuria can also be associated with renal (kidney) disease, as well as hematologic disorders involving the body's clotting system. Medications that increase the risk of bleeding, such as aspirin, warfarin (Coumadin), or clopidogrel (Plavix), may also lead to bloody urine. Lastly, cancer anywhere along the urinary tract can present with hematuria.