Seeing blood in your urine can cause more than a little anxiety. Yet blood in urine — known medically as hematuria — isn’t always a matter for concern. Strenuous exercise can cause blood in urine, for instance. So can a number of common drugs, including aspirin. But urinary bleeding can also indicate a serious disorder. There are two types of blood in urine. Blood that you can see is called gross hematuria. Urinary blood that’s visible only under a microscope is known as microscopic hematuria and is found when your doctor tests your urine for another condition. Either way, it’s important to determine the reason for the bleeding.
The only visible sign of hematuria is pink, red or cola-colored urine — the result of the presence of red blood cells. It takes very little blood to produce red urine, and the bleeding usually isn’t painful. Bloody urine often occurs without other signs or symptoms. In many cases, you can have blood in your urine that’s only visible under a microscope (microscopic hematuria).
The urinary tract is made up of your bladder, your two kidneys and ureters, and the urethra. The kidneys remove waste and excess fluid from your blood and convert it to urine. The urine then flows through two hollow tubes (ureters) — one from each kidney — to your bladder, where urine is stored until it passes out of your body through the urethra. 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 are particularly common in women, though men also get them. They occur when bacteria enter your body through the urethra and begin to multiply in your bladder. The infections sometimes, though not always, develop after sexual activity. 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. About 30 percent of people with a urinary tract infection have visible bleeding.
Other urinary tract infections. Kidney infections (pyelonephritis) can occur when bacteria enter your kidneys from your bloodstream or move from 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 turn into 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 no mistaking the symptoms — kidney stones can cause excruciating pain. They can also cause both gross and microscopic bleeding.
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 is often the first 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 chronic shortage of red blood cells — can be the cause of blood in urine, both gross 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. Common drugs that can cause visible urinary blood include aspirin, penicillin, the blood thinners warfarin and heparin, and the anti-cancer drug cyclophosphamide (Cytoxan).
Strenuous exercise. It’s not quite clear why exercise causes gross hematuria. It may be 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.
A medical history and physical exam play a key role in finding the cause of urinary bleeding. So do urine tests. Even if your bleeding was first discovered through urinalysis, you’re likely to have another test to see if your urine still contains red blood cells. Hematuria that occurs just once usually doesn’t need further evaluation. Urinalysis can also help determine if you have a urinary tract infection or are excreting minerals that cause kidney stones.
Sometimes your doctor may recommend additional tests, including:
- Imaging tests. Most people with hematuria are likely to have an imaging test that provides detailed images of their internal organs. This might be a computerized tomography (CT) scan, which uses radiation and a powerful computer to create cross-sectional images of the inside of the body; magnetic resonance imaging (MRI), which uses a magnetic field and radio waves instead of X-rays to produce images; or an ultrasound exam. Ultrasound uses a combination of high-frequency sound waves and computer processing to view your kidneys and bladder.
- Cystoscopy. In this procedure, your doctor threads a narrow tube fitted with a miniature camera into your bladder to closely examine both the bladder and urethra.
In spite of testing, the cause of urinary bleeding may never be found. In that case, your doctor is likely to recommend regular follow-up tests, especially if you have risk factors for bladder cancer such as smoking, exposure to environmental toxins and a history of radiation therapy.
Hematuria has no specific treatment.
There are steps you can take to reduce your risk of some of the diseases that cause it. For instance, drinking plenty of water, urinating when you feel the urge and as soon as possible after intercourse, and avoiding irritating feminine hygiene products may reduce your risk of urinary tract infections. Other prevention strategies include:
Kidney stones. To help lower the likelihood of kidney stones, drink lots of water and limit salt, protein, and oxalate-containing foods such as spinach and rhubarb.
Bladder cancer. Stopping smoking, avoiding exposure to chemicals, drinking plenty of water, and eating more cabbage and broccoli can cut your risk of bladder cancer.
Kidney cancer. To help prevent kidney cancer stop smoking, maintain a healthy weight, up your intake of fruits and vegetables, stay active, and avoid exposure to toxic chemicals.