Hematuria (Blood in the Urine)

What hematuria means

Healthy urine contains almost no red blood cells. Hematuria means there are more than normal, at least 3 red blood cells per high-power microscope field on two or more samples for microscopic hematuria, according to the American Urological Association.

Blood can enter the urine anywhere along the urinary tract: the kidneys, ureters, bladder, prostate or urethra.

Gross vs microscopic hematuria

For an everyday explanation of red urine, its look-alikes and first steps, see blood in urine.

Things that look like blood but are not

• Foods: beets, blackberries and rhubarb.
• Medicines: phenazopyridine (orange), rifampin, nitrofurantoin and some laxatives.
• Muscle breakdown (myoglobin) after extreme exercise or crush injury, which causes dark urine without red cells.
• Menstrual blood contaminating the sample.

A dipstick may be positive for blood when no red cells are seen on microscopy. That points to myoglobin or hemoglobin rather than bleeding.

Causes of hematuria

Infections and inflammation

• Urinary tract infection: burning, frequency and urgency with cloudy urine.
• Kidney infection: fever, side pain and vomiting.
• Urethritis from sexually transmitted infections.
• Radiation cystitis after pelvic radiotherapy.

Stones and blockage

• Kidney stones: severe, colicky pain from the side to the groin, with nausea. Small stones can cause microscopic blood alone.
• Enlarged prostate: fragile surface vessels can bleed, with a weak stream and frequent urination.

Cancers

• Bladder cancer: the classic cause of painless visible hematuria. Smoking is the biggest risk factor, plus exposure to dyes, rubber and some industrial chemicals.
• Kidney cancer: sometimes with a side mass or pain.
• Prostate and upper urinary tract cancers.

Kidney diseases (glomerular causes)

Inflammation of the kidney filters (glomerulonephritis) causes cola-colored urine, protein in the urine, swelling and high blood pressure. Causes include IgA nephropathy (often with visible blood 1 to 2 days after a sore throat), post-streptococcal glomerulonephritis (1 to 3 weeks after a strep infection), lupus, thin basement membrane disease and Alport syndrome. See nephritic syndrome. Polycystic kidney disease can also cause bleeding.

Other causes

• Vigorous exercise, especially long-distance running, which usually clears within 24 to 72 hours.
• Injury to the kidney or bladder.
• Recent catheter, cystoscopy or prostate biopsy.
• Blood thinners: they may reveal bleeding from an underlying lesion, so they are not accepted as the sole explanation.
• Sickle cell trait or disease.
• Endometriosis of the bladder, with cyclical bleeding.
• In children: infections, post-infectious glomerulonephritis, kidney abnormalities and high calcium in the urine.

Risk factors for a serious cause

The AUA groups adults by risk. Factors that increase the chance of cancer include:

• age over 40 to 60
• male sex
• smoking, current or past (the strongest risk factor)
• visible blood, or many red cells on testing
• occupational exposure to dyes, rubber, leather or petrochemicals
• previous pelvic radiation or cyclophosphamide treatment

How hematuria is evaluated

1. History and examination: pain, urinary symptoms, recent infections, exercise, medicines, smoking and family kidney disease. Blood pressure and swelling are checked.
2. Urinalysis with microscopy: confirms red cells. Misshapen (dysmorphic) red cells and red cell casts suggest kidney inflammation.
3. Urine culture: for infection. If an infection is treated, the test is repeated afterward to confirm the blood has cleared.
4. Blood tests: kidney function (creatinine and eGFR) and a blood count.
5. Imaging: a CT urogram for most adults with visible blood or high-risk microscopic blood. Ultrasound is used for lower risk, in pregnancy, or when kidney function is poor.
6. Cystoscopy: a thin camera through the urethra to examine the bladder lining. It is the best test for bladder cancer.
7. Kidney referral: to a nephrologist if there is protein in the urine, abnormal kidney function or signs of glomerular disease, sometimes with a kidney biopsy.

Treatment

Hematuria is treated by treating its cause:

• antibiotics for infection
• pain relief, fluids and sometimes procedures for stones
• medicines or surgery for an enlarged prostate
• surgery, intravesical therapy, chemotherapy or immunotherapy for cancers
• blood pressure control and immune treatments for glomerular disease

Occasionally no cause is found. Low-risk people may then simply have repeat urine tests. Anyone with new visible blood later should be re-evaluated.

Frequently asked questions

What is hematuria?

Hematuria is the presence of red blood cells in the urine. Gross hematuria is visible as pink, red or brown urine. Microscopic hematuria is detected only by a urine test. It is a sign, not a diagnosis, and has many possible causes from infection to cancer.

What is the difference between gross and microscopic hematuria?

Gross hematuria is blood you can see in the urine. Microscopic hematuria is blood seen only under the microscope or on a dipstick. Visible blood carries a higher risk of a serious cause such as bladder cancer, so it nearly always needs imaging and cystoscopy in adults.

Is painless hematuria serious?

It can be. Painless visible blood in the urine is the most common first sign of bladder cancer, especially in smokers and people over 40. It should always be evaluated by a doctor, even if it happens only once and goes away by itself.

Can exercise cause blood in urine?

Yes. Intense or long-distance exercise can cause temporary hematuria, often clearing within 72 hours. If blood persists after a few days of rest, or appears without heavy exercise, further testing is needed to exclude other causes.

What tests are done for hematuria?

Doctors usually start with urinalysis, urine microscopy and a urine culture, plus blood tests for kidney function. Adults with visible or higher-risk blood usually have a CT urogram or ultrasound of the kidneys and a cystoscopy to look inside the bladder.