White Blood Cell -WBC
Normal urine may contain up to 4-5 WBC on microscopic examination. Increased numbers of WBC in the urine indicates an acute infection at some point in the urinary tract. Infection can be diagnosed by doing a urine culture test.
Red Blood Cell – RBC
Normal urine may contain up to 2-3 RBC on microscopic examination. Presence of a large amount of RBCs indicates urinary tract and renal disease or trauma. Strenuous exercise can also result in a high count.
Epithelial Cells (EC)
The few epithelial cells routinely found in normal urine represent the sloughing off of aging tissue. Most frequently, these are squamous cells originating from the superficial layers of the urinary tract or vagina and have no pathologic significance. The presence of renal cells from the lining of the kidney, ureters or bladder indicates pathologic or inflammatory conditions in the upper urinary tract. Large numbers of renal EC’s strongly suggest active degeneration of the kidney tubules. High counts in urine from females may be due to contamination from vaginal discharge.
Casts are formed when protein accumulates and precipitates in the kidney tubules and is washed into the urine. The presence of increased numbers of any type of cast in the urine usually accompanies an increase in protein and indicates the existence of renal disease. Presence of a few casts may be seen in the urine of a normal person after exercise.
Crystals in the urine are not present at time of voiding but form as the specimen stands and cools. The formation of crystals is influenced by the pH and temperature of the urine. Although most crystals have no health significance, there are some rare crystals which appear because of certain amino acid metabolic disorders, and in patients taking sulfa drugs or other medications that are not very soluble. Presence of crystals in large amounts and for prolonged periods may lead to formation of kidney stone.
Bacteria in a urine specimen may or may not be significant depending on how the urine was collected and how soon after collection it was examined. The presence of large numbers of bacteria in fresh urine is definitely abnormal. Significant numbers of bacteria reported upon microscopic examination suggest the presence of infection.
Mucus threads are usually present in small numbers. Increased numbers are indicative of chronic inflammation of the urethra and bladder.
Yeast can occur as a common contaminant from skin and air. Candida albicans is a common urinary finding in patients with diabetes mellitus.