Testing urine gives a clear indication of the health of the kidneys and the urinary tract. Spun down, concentrated urine can be viewed under a microscope, and certain types of cells isolated. Some types of cells found in urine are perfectly normal, while others are normally present only in small quantities; still others are never found in normal urine.
Bacteria
Small amounts of bacteria may be seen in normal sediment. While urine is normally sterile, the urethra and vagina may contain bacterial contamination. If a urine sample sits for some time before being examined, it's likely to contain a large amount of bacteria, which may have no significance.
Blood Cells
Red and white blood cells, called leukocytes, may be found in small numbers in a normal urine sample. Most are contaminates from the vaginal tract or from menstruation in women. Fever or violent exercise can also account for the presence of red blood cells, in some cases.
Casts
Casts form in the kidney tubules and generally indicate kidney disease. Seven different types of casts exist; hyaline casts are the most common. A few hyaline casts in a urine sample generally don't indicate a problem with the kidneys. Exercise, dehydration or diuretic use may cause the presence of a few hyaline casts, Medline Plus reports. Fever and emotional stress may also cause a temporary increase in hyaline casts. Other types of casts, such as waxy, granular, and red and white blood cell casts, don't normally occur in urine.
Crystals
Crystals frequently occur in normal urine specimens. Different types of crystals include calcium oxalate, crystalline uric acid, calcium carbonate and amorphous urates and phosphates.
Epithelial Cells
Epithelial cells, or skin cells, often appear in small amounts in urine, either from the bladder or from the urethra. Epithelial cells from the kidney typically do not appear in a normal urine specimen.
