Hematuria is the presence of red blood cells in the urine. If there are enough red cells, the urine can become bright red, pink or cola colored. Often, however, the urine appears completely normal because there is not enough blood to cause a color change. In this case, the condition is called "microscopic" hematuria.
There are many possible causes of hematuria, including:
Urinary tract infection — Hematuria can be caused by an infection in any part of the urinary tract, most commonly the bladder (cystitis) or the kidney (pyelonephritis).
Tumors in the kidney or bladder
Exercise — Exercise hematuria is a harmless condition that produces blood in the urine after strenuous exercise. It is more common in males than females.
Trauma — Traumatic injury to any part of the urinary tract — from the kidneys to the urethral opening (the connection between the bladder and the outside world) — can cause hematuria.
Drugs — Hematuria can be caused by medications, such as blood thinners, including heparin, warfarin (Coumadin) or aspirin-type medications, penicillins, sulfa-containing drugs and cyclophosphamide (Cytoxan).
Glomerulonephritis — Glomerulonephritis is a family of illnesses that are characterized by inflammation of the glomeruli, the filtering units of the kidneys. Glomerulonephritis is a rare complication of certain viral and bacterial infections (including strep throat). It can also occur in people with certain auto-immune diseases, systemic lupus erythematosus (lupus or SLE) and vasculitis. Sometimes there is no identifiable cause.
Bleeding disorders — These include the family of hemophilias.