"Microscopic" means something is so small that it can only be seen through a special tool called a microscope. "Hematuria" means blood in the urine. So, if you have microscopic hematuria, you have red blood cells in your urine, but you can't see the blood when you urinate.
Here are some common causes of blood in the urine:
Your doctor will usually start by asking you for a urine sample. He or she will test your urine (urinalysis) for the presence of red blood cells. Your doctor will also check for other things that might explain what is wrong. For example, white blood cells in your urine usually mean that you have an infection. If you have blood in your urine, your doctor will ask you some questions to find out what caused it.
If the cause isn't clear, you may have to have more tests. You might have an ultrasound or an intravenous pyelogram (this is like an X-ray). A special tool, such as a cytoscope or an endoscope, may be used to look inside of your bladder. These tests are usually done by a urologist.
A nurse will give you an antiseptic wipe (to clean yourself) and a sterile urine collection cup. In the bathroom, wash your hands with soap and warm water first.
If the cause of the blood in your urine is clear, your doctor will probably treat you. Then your doctor will check your urine again to see if the blood is gone. If it's not, your doctor may perform more tests or refer you to a urologist.
Remember that it is always important to find out the cause of blood in your urine.
Evaluation of Asymptomatic Microscopic Hematuria in Adults by TR Thaller, M.D. and LP Wang, M.D. (American Family Physician September 15, 1999, http://www.aafp.org/afp/990915ap/1143.html)
Written by familydoctor.org editorial staff