This description aims to provide patients with some useful information on the tests which may be included as part of their health screening. The tests are explained briefly. Because reference ranges are typically defined as the range of values of the median 95% of the healthy population, it is unlikely that a given specimen, even from a healthy individual, will show “normal” values for all tests. All results should be correlated with patient’s history and clinical findings. Therefore, your physician is the best person to interpret your laboratory results. Always consult your physician.
Normal urine may contain up to three RBCs per high power field. It should be noted that in urine microscopy, only intact RBCs are detected. Excess RBCs in urine may indicate a variety of renal and systemic diseases, including trauma to the kidney and presence of kidney stones. Excess RBCs in urine may also be found after strenuous exercises. In females, menstrual blood can sometimes contaminate the urine sample.
Normal urine may contain up to five WBCs per high power field. The presence of a large number of WBCs usually indicates bacterial infection in the urinary tract.
Squamous epithelial cells appear frequently in normal urine. A large number of renal epithelial cells may indicate active degeneration of the renal tubules.
Casts are formed when protein accumulates and is deposited in the kidney tubules and is washed into the urine. Casts are named according to the cells contained in them. For example, RBC cast, WBC cast. The presence of a large number of any type of casts in the urine usually accompanies an increase in protein excretion and indicates existing renal disease. An occasional cast may be found in urine of normal people especially after exercise.
A variety of crystals may appear in the urine. These can be identified by their specific appearances and solubility characteristics. Most crystals are of little diagnostic significance while some, however, indicate pathology. Phosphate crystals are common in alkaline urine. Oxalate crystals are found in acid urine. Uric acid crystals usually occur in high uric acid excretors and in some normal people.