In hematuria, your kidneys — or other parts of your urinary tract — allow blood cells to leak into urine. A number of problems can cause this leakage, including:

  • Urinary tract infections. Urinary tract infections often occur when bacteria enter your body through the urethra and begin to multiply in your bladder. Symptoms can include a persistent urge to urinate, pain and burning with urination, and extremely strong-smelling urine.

    For some people, especially older adults, the only sign of illness may be microscopic blood.

  • Kidney infections. Kidney infections (pyelonephritis) can occur when bacteria enter your kidneys from your bloodstream or move up from your ureters to your kidney(s). Signs and symptoms are often similar to bladder infections, though kidney infections are more likely to cause fever and flank pain.
  • A bladder or kidney stone. The minerals in concentrated urine sometimes precipitate out, forming crystals on the walls of your kidneys or bladder. Over time, the crystals can become small, hard stones. The stones are generally painless, and you probably won't know you have them unless they cause a blockage or are being passed. Then there's usually no mistaking the symptoms — kidney stones, especially, can cause excruciating pain. Bladder or kidney stones can also cause both gross and microscopic bleeding.
  • Enlarged prostate. The prostate gland — located just below the bladder and surrounding the top part of the urethra — often begins growing as men approach middle age. When the gland enlarges, it compresses the urethra, partially blocking urine flow.

    Signs and symptoms of an enlarged prostate (benign prostatic hyperplasia, or BPH) include difficulty urinating, an urgent or persistent need to urinate, and either visible or microscopic blood in the urine. Infection of the prostate (prostatitis) can cause the same signs and symptoms.

  • Kidney disease. Microscopic urinary bleeding is a common symptom of glomerulonephritis, which causes inflammation of the kidneys' filtering system.

    Glomerulonephritis may be part of a systemic disease, such as diabetes, or it can occur on its own. It can be triggered by viral or strep infections, blood vessel diseases (vasculitis), and immune problems such as IgA nephropathy, which affects the small capillaries that filter blood in the kidneys (glomeruli).

  • Cancer. Visible urinary bleeding may be a sign of advanced kidney, bladder or prostate cancer. Unfortunately, you may not have signs or symptoms in the early stages, when these cancers are more treatable.
  • Inherited disorders. Sickle cell anemia — a hereditary defect of hemoglobin in red blood cells — can be the cause of blood in urine, both visible and microscopic hematuria. So can Alport syndrome, which affects the filtering membranes in the glomeruli of the kidneys.
  • Kidney injury. A blow or other injury to your kidneys from an accident or contact sports can cause blood in your urine that you can see.
  • Medications. The anti-cancer drug cyclophosphamide (Cytoxan) and penicillin can cause urinary bleeding. Visible urinary blood sometimes occurs if you take an anticoagulant, such as aspirin and the blood thinner heparin, and you also have a condition that causes your bladder to bleed.
  • Strenuous exercise. Although it happens rarely, it's not quite clear why strenuous exercise may lead to gross hematuria. It may be linked to trauma to the bladder, dehydration or the breakdown of red blood cells that occurs with sustained aerobic exercise. Runners are most often affected, although almost any athlete can develop visible urinary bleeding after an intense workout.

Whatever the cause, contact your doctor right away if you see blood in your urine.

Aug. 29, 2014

You Are ... The Campaign for Mayo Clinic

Mayo Clinic is a not-for-profit organization. Make a difference today.