Gross hematuria (visible blood in the urine) can be caused by several things other than cancer. A urinary tract infection, a kidney stone, a bladder stone, chronic irritation in the bladder, many kidney diseases, and other less common conditions all can cause hematuria. Men with large prostates who strain to void may get bleeding because of rupture of small veins in the prostate. Occasionally, long-distance runners can develop hematuria, presumably because of bladder irritation from the repetitive bouncing.
Also, patients who have had pelvic radiation to treat other cancers may develop radiation cystitis. Radiation cystitis is a benign but troublesome condition because it may cause persistent bleeding in the bladder that can be difficult to fully stop. Although many of these processes are benign and do not require treatment, a urologist needs to evaluate any blood in the urine to rule out the presence of a tumor.
Microscopic hematuria can only be seen in the laboratory on a urine sample. It is defined as three or more red blood cells seen per high-power field under the microscope. In the office, many physicians use a urine dipstick to test the urine for blood, but the test is overly sensitive. The test may be falsely positive because of menstruation, some antiseptics, recent exercise, dehydration, or the use of a large amount of vitamin C.
The dipstick is a strip of paper that is treated with chemicals. Microscopic amounts of blood in the urine react with the chemicals to change their color. Any urine that shows blood on the dipstick test needs to be looked at under the microscope to determine whether blood is really present. All of the processes mentioned previously here for gross hematuria can also cause microscopic hematuria. In both gross and microscopic hematuria, the first task is to determine where the blood is coming from—that is, one kidney, both kidneys, the ureter, the bladder, the prostate, or the urethra . Women may notice blood on the toilet paper and assume that they have hematuria. This can be the case; however, we must first be sure it is not vaginal or uterine bleeding.
In addition to these medical causes of hematuria, several nonmedical things can often be mistaken for hematuria. Eating an inordinately large number of beets can color the urine red. Dehydration can cause the urine to become quite concentrated and dark, giving the impression of hematuria. Pyridium, which numbs the urinary tract and is often prescribed during a urinary tract infection, will turn the urine a bright orange.