Blood in the urine is also called hematuria. Normally, urine does not contain any blood.

There are two kinds of hematuria:

• Microscopic hematuria—Urine contains a very small amount of blood, which is not visible to the naked eye.
• Gross hematuria—Urine is visibly discolored by blood, appearing red or tea-colored.

In some cases, the cause of hematuria is never found. The list of known causes is lengthy. Some more common causes include:

• Injury to the abdomen, pelvis, or internal organs of the urinary tract
• Vigorous exercise (resolves with rest)
• Urinary tract infection or kidney infections
• Cancer of the prostate, kidney, or bladder
• Kidney disease
• Kidney stones
• Bleeding disorders (eg, hemophilia)
• Certain congenital diseases (eg, polycystic kidneys)
• Radiation of the pelvis (for cancer treatment)
• Certain medications

Risk factors include:

• Smoking
• Medicines (eg, certain antibiotics and pain medicines)
• Recent upper respiratory tract infection
• Family history of kidney problems

Kidney Stones Can Cause Microscopic Hematuria

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In some cases, there may not be additional symptoms.

But, if you have an underlying condition, you may have other symptoms. For example, kidney stones can cause blood in the urine, along with pain in the side, abdomen, or groin.

Your doctor will ask about your symptoms and medical history, and perform a physical exam. You may be referred to a doctor who specializes in kidney disease (nephrologist) or the urinary system (urologist).

Tests may include:

• Urine tests—tests to confirm the presence of blood and look for protein, bacteria, or cancer cells in the urine
• Blood tests—tests to check how well the kidneys are functioning and to look for medical conditions that cause hematuria
• X-ray—performed with contrast material injected into a vein to look at the function and structure of the kidneys, ureters, and bladder
• Ultrasound—a test that uses sound waves to create images of the kidneys and urinary tract
• CT scan—a type of x-ray that uses a computer to create images of the kidneys and urinary tract
• MRI scan—a test that uses powerful magnets and radio waves to create images of the kidneys and urinary tract
• Cystoscopy—a thin tube inserted through the urethra and into the bladder to look at its lining

Treatment will depend on the underlying cause of hematuria. Some causes of hematuria require no treatment (eg, exercise-induced) or will resolve on their own (eg, passage of a kidney stone). Other causes will respond to medicine. For example, treating a urinary tract infection with antibiotics will stop the hematuria. Still other causes may require surgery, such as the removal of a bladder or treatment for prostate cancer.

Treating the underlying condition that causes hematuria may help prevent it from occurring.