Hematuria (Blood in the Urine)
Blood in the urine can be visible or microscopic and may have many possible causes, ranging from no serious underlying issue to infection, stones, kidney disease, or urinary tract cancer.
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Understanding Blood in Your Urine
Blood visible in the urine or detected on a urine test
Possible urinary tract infection, stone disease, kidney disease, or urinary tract irritation
Need for evaluation when gross hematuria or significant microscopic hematuria is present
What Is Hematuria?
Hematuria is the presence of red blood cells in the urine. It can be characterized as either gross hematuria, which is visible to the naked eye, or microscopic hematuria, which is only visible under a microscope.
Microscopic hematuria is often found incidentally on urine tests during a routine medical evaluation. Gross hematuria may prompt someone to visit the doctor because the blood is visible. Hematuria can originate from any site along the urinary tract, including the kidneys, ureters, bladder, prostate, and urethra.
Hematuria is estimated to occur in 2.5% to 21% of the population. In many patients, no specific cause is found. However, hematuria may be a marker for infection, stone disease, or urinary tract cancer. Risk factors for significant underlying disease include smoking, radiation, overuse of some pain medicines, and exposure to certain chemicals.
Causes, Testing, and Follow-Up
Blood in the urine is often not a sign of significant disease. Studies have shown that between 9% and 18% of normal individuals can have some degree of hematuria. However, hematuria can also be a sign of an important medical condition that requires treatment.
Common causes of hematuria include cancer of the bladder, kidney, urethra, or ureter; urinary stone disease; urinary tract infection; kidney disease; radiation- or chemical-induced cystitis, which is bladder irritation; injury to the urinary tract; and exercise-induced hematuria.
Visible hematuria is often worrisome and may prompt someone to seek medical attention. Microscopic hematuria can be just as severe, even though it often has no symptoms and is detected on a urine dipstick test. If the dipstick test is positive for blood, the amount of blood is often determined by looking at the urine under a microscope. If three or more red blood cells are seen per high-power field on two of three specimens, further evaluation to determine a cause is recommended.
Any patient with gross hematuria or significant microscopic hematuria should have further evaluation of the urinary tract. This typically begins with a careful history and physical examination. Laboratory analysis may include urinalysis, examination of urinary sediment under a microscope, evaluation for protein, evidence of urinary tract infection, urine culture when white blood cells are present, urinary cytology to look for abnormal cells, and a blood test to measure serum creatinine, which is a measure of kidney function.
A complete urologic evaluation may also include imaging of the kidneys and ureters to detect kidney masses, tumors of the ureters, or urinary stones. Imaging options may include intravenous pyelogram, renal ultrasound, computerized tomography scan, CT urography, magnetic resonance imaging, or retrograde pyelography. Because imaging studies cannot fully evaluate the bladder, cystoscopic evaluation is also required. During cystoscopy, the doctor examines the inner lining of the bladder and urethra using a cystoscope.
If no cause is found, some form of follow-up is recommended because urologic malignancy is later discovered in 1% to 3% of patients with negative work-ups. Follow-up may include repeat urinalysis and urine cytology at six, 12, 24, and 36 months. Immediate re-evaluation with possible cystoscopy and repeat imaging should be performed if gross hematuria, abnormal urinary cytology, or irritating urinary symptoms such as pain with urination or increased frequency occur.
Frequently Asked Questions
What is hematuria?
Hematuria is the presence of red blood cells in the urine. It may be gross, meaning visible to the naked eye, or microscopic, meaning it is only visible under a microscope.
What can cause blood in the urine?
Common causes include urinary tract infection, urinary stone disease, kidney disease, injury to the urinary tract, radiation- or chemical-induced bladder irritation, exercise-induced hematuria, or cancer of the bladder, kidney, urethra, or ureter.
Is blood in the urine always serious?
Blood in the urine is often not a sign of significant disease, and some people have no specific cause found. However, hematuria can also be a marker for infection, stone disease, or urinary tract cancer, so further evaluation may be recommended.
How is hematuria diagnosed?
Hematuria may be detected through a urine dipstick test and confirmed by examining urine under a microscope. A doctor may also perform a history and physical exam, urinalysis, urine culture, urinary cytology, blood testing, imaging, and cystoscopy depending on the findings.
What happens if no cause is found?
In at least 8% to 10% of cases, no cause is found. Because a small percentage of patients with negative work-ups are later found to have urologic malignancy, follow-up may be recommended.
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