Blood in the urine (hematuria) can make urine appear pink, red, or brown, depending on the amount of blood, how long it has been in the urine, and how acidic the urine is. An amount of blood too small to change color of the urine (microscopic hematuria) may be found by chemical tests or microscopic examination. Microscopic hematuria may be found when a urine test is done for another reason.
People with hematuria may have other symptoms of urinary tract disorders, such as pain in the side or back (flank), lower abdominal pain, an urgent need to urinate, or difficulty urinating, depending on the cause of blood in the urine. If sufficient blood is present in the urine, the blood may form a clot. The clot can completely block the flow of urine, causing sudden extreme pain and the inability to urinate. Bleeding severe enough to cause such a clot is usually caused by an injury to the urinary tract.
Red urine is not always caused by red blood cells. Red or reddish brown discoloration may also result from the following:
Hemoglobin (which carries oxygen in red blood cells) in the urine due to the breakdown of red blood cells
Muscle protein (myoglobin) in urine due to the breakdown of muscle cells
Porphyria (a disorder caused by deficiencies of enzymes involved in the production of heme, a chemical compound that contains iron and gives blood its red color)
Foods (for example, beets, rhubarb, and sometimes food coloring)
Causes of Blood in Urine
Blood in the urine may be caused by problems anywhere along the urinary tract from the kidneys to the ureters, bladder, or urethra. Some women at first mistake vaginal bleeding for blood in the urine.
Common causes
The most common causes differ somewhat by the person's age but overall are
Bladder infection (cystitis)
Prostate infection (prostatitis)
Urinary tract stones (in adults)
Less common causes
Less common causes include
Noncancerous enlargement of the prostate (benign prostatic hyperplasia)
Disorders of the small blood vessels of the kidneys (called kidney filtering disorders or glomerular disorders)
Cysts in the kidneys (polycystic kidney disease)
Narrowing scars (called strictures) or other abnormalities of the ureters
Cancer and benign prostatic hyperplasia may cause blood in the urine. These disorders are a concern mainly in people over 50, although younger people with risk factors (smoking, family history, or chemical exposures) may develop cancer.
Disorders of the microscopic blood vessels of the kidneys (glomeruli) can be a cause at any age.
Kidney filtering disorders (glomerular disorders) may be part of a kidney disorder or may occur as a result of a disorder elsewhere in the body. These disorders are more likely if the urine has protein, clumps of red blood cells (called red blood cell casts), or malformed red blood cells. Such disorders include infections (such as a heart valve infection), connective tissue disorders (such as systemic lupus erythematosus) and vasculitis, blood disorders (such as serum sickness), or certain chronic disorders (such as diabetes). Also, almost any kind of kidney damage may cause small amounts of blood in the urine.
Severe injuries, such as from a fall or a motor vehicle crash, can injure the kidneys or bladder and cause bleeding. Various procedures and surgeries (for example, inserting a catheter or doing a prostate or kidney biopsy) can also cause bleeding.
Schistosoma haematobium is a parasitic worm that causes a disease called schistosomiasis in Africa and, to a lesser extent, in India and parts of the Middle East. This worm can invade the urinary tract, causing blood in the urine. Doctors consider schistosomiasis only if people have spent time in areas where the worm is found. Tuberculosis may cause blood in the urine.
Other causes of blood in the urine include bladder inflammation from radiation therapy of the pelvic region, certain drugs, and blood vessel disorders of the kidney.
Because blood in the urine of a person taking an anticoagulant (a "blood-thinner" that prevents blood clots) is not necessarily caused by that medication, the doctor's evaluation will take all other potential causes into consideration.
Evaluation of Blood in Urine
Doctors first try to establish that bleeding is the cause of red urine. Then they look for the cause of the bleeding, including where in the urinary tract (or occasionally elsewhere) the bleeding is originating. The following information can help people know when to see a doctor and what to expect during the evaluation.
Warning signs
In people with blood in the urine, certain symptoms and characteristics are cause for concern. They include
Large amount of blood in the urine
Age over 50
Swelling of the feet or legs, plus high blood pressure
When to see a doctor
People who notice blood in their urine should see their doctor within 1 or 2 days. However, people who are passing a large amount of blood, who are unable to urinate, or who have severe pain should see a doctor right away.
What the doctor does
Doctors first ask questions about the person's symptoms and medical history and then do a physical examination. What they find during the history and physical examination often suggests a cause of the blood in the urine and the tests that may need to be done (see table Some Causes and Features of Blood in the Urine).
Doctors ask how long blood has been present and whether there have been any previous bleeding episodes. They ask about fever, weight loss, or symptoms of urinary blockage, such as difficulty starting urination or inability to completely empty the bladder. Pain or discomfort is an important finding. Burning during urination or dull pain in the lower abdomen just above the pubic bone suggests a bladder infection. In men, mild to moderate pain in the lower back or pelvis is often the result of a prostate infection. Extremely severe pain is usually due to a stone or a blood clot blocking the flow of urine.
Doctors then do a physical examination. Usually, a pelvic examination is necessary in women. If women have blood in the vagina, a catheter may need to be inserted into the bladder to see whether the source of blood is the bladder or the vagina. In men, doctors usually do a digital rectal examination to check the prostate.
Some Causes and Features of Blood in the Urine
Cause | Common Features* | Tests† |
|---|---|---|
Benign prostatic hyperplasia (noncancerous enlargement of the prostate gland) | Mainly in men over 50 Often difficulty starting urination, a weak urine stream, a sensation of incomplete urination, or dribbling at the end of urination An enlarged prostate detected during a digital rectal examination | Blood tests to measure the PSA level Often ultrasonography of the bladder to measure how much urine remains in the bladder after voiding (postvoid residual urine volume) |
Mainly in people over 50 or with risk factors for these cancers (smoking, family members who have had cancer, or exposure to chemicals that may cause cancer) Sometimes burning or pain during urination or an urgent need to urinate Often symptoms that affect the whole body (such as fever, chills, weight loss or sweating) | Examination of the interior of the bladder using a flexible viewing tube inserted through the urethra (cystoscopy) Possible bladder biopsy Sometimes CT or MRI If prostate cancer is suspected, prostate biopsy | |
Cystitis (bladder infection) | Usually in women and girls A frequent and urgent need to urinate Burning or pain during urination Getting up at night to urinate Sometimes blood in the urine or foul-smelling urine | A doctor's examination Usually urinalysis and urine culture |
Injury | Usually an obvious injury | Usually CT of the abdomen and pelvis |
Kidney filtering disorders (glomerular disorders, such as glomerulonephritis) | Sometimes high blood pressure and swelling in the feet or legs Sometimes protein in the urine, malformed red blood cells, clumps of red blood cells, and/or decreased kidney function Possibly red or dark (cola-colored) urine Sometimes occurring after an infection Sometimes in people who have family members with a kidney or a connective tissue disorder | Urinalysis Blood tests |
Long-lasting pain in the flank or abdomen High blood pressure Sometimes enlarged kidneys detected on an imaging test done for another reason or during a doctor's examination | Ultrasonography Often CT or MRI of the abdomen | |
Mainly in men over 50 Sometimes a lump in the prostate detected during a digital rectal examination Occasionally a weak urine stream, difficulty starting urination, and dribbling at the end of urination | Blood tests to measure the PSA level If the PSA level is elevated, biopsy of the prostate | |
Prostatitis (infection of the prostate gland) | Often fever, difficulty starting urination, frequent urination, the need to urinate during the night, and burning or pain during urination Often symptoms of a long-standing blockage in the urinary tract (including a weak urine stream, difficulty passing urine, or dribbling at the end of urination) In an acute infection, an enlarged, tender prostate detected during a digital rectal examination; in chronic prostatitis, there may not be any significant symptoms | A doctor's examination Urinalysis and urine culture Sometimes transrectal ultrasonography or cystoscopy |
Usually in people already known to have sickle cell disease Mainly in people of African or Mediterranean descent Often in children and young adults | Blood tests to check for abnormal hemoglobin in red blood cells | |
Severe pain in the lower back side (flank) that occurs suddenly or pain in the abdomen or groin that comes in waves Sometimes the urge to urinate but an inability to do so Sometimes vomiting | CT or ultrasonography of the kidneys, ureters, and bladder | |
* Features include symptoms and the results of a doctor's examination. Features mentioned are typical but not always present. | ||
† Tests include urinalysis in all people, blood tests to evaluate renal function in most people, and imaging of the kidneys and pelvis in most older adults. | ||
CT = computed tomography; MRI = magnetic resonance imaging; PSA = prostate-specific antigen. | ||
Testing
Sometimes doctors can make a diagnosis based on the person's symptoms and the results of the physical examination. More often, because symptoms of many disorders overlap, testing is needed to determine the cause (or sometimes the presence) of blood in the urine. Urinalysis is the first test done. Urinalysis can detect blood (confirming that the red color of the urine is caused by blood) and may show evidence of a kidney filtering disorder. If infection is suspected, urine culture is usually done.
In all people over 50 and in people who have risk factors for cancer, doctors typically use a flexible viewing tube to look inside the bladder (cystoscopy) to determine the cause of bleeding.
People of any age who do not have an infection or a kidney filtering disorder as the cause of visibly bloody urine typically have imaging studies, such as computed tomography (CT), ultrasonography, or magnetic resonance imaging (MRI) of the abdomen and pelvis. For people under 50 who have only microscopic hematuria and no other abnormalities detected during the physical examination, blood tests, or urinalysis, doctors may simply repeat the urinalysis in 6 or 12 months. If blood is still present, they will do further tests.
If doctors suspect a kidney filtering disorder (based of the results of urinalysis), they usually do blood tests to evaluate kidney function and sometimes a kidney biopsy. Blood tests for sickle cell disease may be needed in people of African or Mediterranean descent who are not known to have the disease.
In men who are 50 or older, doctors usually measure the level of prostate-specific antigen (PSA) in the blood.
Treatment of Blood in Urine
Treatment is directed at the cause of the bleeding. Whatever the cause, if urine flow is blocked by blood clots, doctors usually insert a flexible tube in the bladder (urinary catheter) and try to flush out the blood clot.
Key Points
Red urine is not always caused by blood.
Many causes of blood in the urine are not serious.
Risk of serious disease increases with age and the duration of the bloody urine.
Testing for cancer is usually needed only for people over 50 or for younger people with risk factors for cancer.
