Doctors call this microscopic hematuria. Hematuria means blood in the urine. Microscopic refers to the fact that the urine looks normal in color but the urine tests positive for blood.

There are two ways to test for microscopic hematuria:

• Put a test strip in the urine
  The strip turns a certain color if hemoglobin (a component of red blood cells) is present in the urine.
• Put some urine in a test tube and spin it in a centrifuge
  This forces any cells and sediment to the bottom of the tube. A doctor or lab technician looks at the sediment under a microscope.

If the test strip is positive, but no red blood cells are seen under the microscope, this might indicate a blood condition or muscle disorder. Red blood cells that are breaking apart release hemoglobin. Some muscle diseases release myoglobin, a cousin of hemoglobin, into the blood. Both get into the urine.

Most likely, your mother's urine did show red blood cells under the microscope. Causes of red blood cells in the urine include:

• Urinary tract infections, such as a bladder infection
• Kidney stones
• Kidney diseases, such as glomerulonephritis
• Bladder tumors
• Kidney tumors

The first step will be to repeat the urine test to see if her urine still tests positive for blood. The doctor will look for white blood cells and bacteria because that would indicate a urinary tract infection.

If your mother continues to have blood in her urine, other tests might include a CT scan or ultrasound of her kidneys and bladder. Another test is called cystoscopy. A doctor inserts a thin, flexible scope into the bladder to look for any growths or other abnormalities.