Urinalysis is a valuable diagnostic method that can relatively easily and quickly detect a large number of disorders and diseases. Urine does not only informs us about the status and function of the urinary tract, but also about the function of kidneys. The urinalysis has more levels depending on the complexity and requirements of the laboratory equipment. The simplest examination using the dipstick is inexpensive and can be easily done even by a family doctor.
The examined person usually urinates into a special tube or a container. Especially for the microbiological examination, it is necessary to obtain a sample of midstream urine, i.e. first portion of urine should go into the toilet and the following into the sampling tube. Urine sample may be also taken by urinary catheterization.
For complex chemical examination, detection of daily loss of ions, proteins and various other compounds, it is often necessary to collect the urine for 24 hours and measure it volume. After that, we take a sample from the collected urine and find out concentration of any desired substance. This concentration and the total volume of the collected urine allows us to calculate the total daily urinary loss of any substance we desire, for example the daily loss of proteins.
Possible ways of urinalysis
1st Chemical analysis by test strips
This is the most basic method of chemical analysis of the urine. It is very easy, low-cost and wide-available, but on the other hand, it is very basic and inaccurate. The principle is that the urine sample is put to direct contact with a stripe of testing paper, whose color changes thanks to chemical reaction.
We can check following attributes:
Sugar presence - Sugar in urine is usually a warning sign that should be followed by checking the blood level of sugar (glycemia) to exclude diabetes. In normal level of blood sugar, no sugar should be present in the urine.
Proteins - Protein presence in the urine is typical for many pathological conditions including kidney diseases, urinary tract infections, or excessive occurrence of certain proteins in the blood (see the text about proteins in urine).
Bilirubin - Bilirubin is a pigment that arises from the breakup of hemoglobin located in red blood cells. The finding of bilirubin in urine indicates the impaired ability of the body to excrete bilirubin by bile, which is usually related to obstructions of biliary tract. Details can be found in a more general text about jaundice.
Ketone bodies - Ketone bodies are formed in the body when we starve or when we suffer from absence of insulin (for example in type 1 diabetes). Therefore, we find ketones in urine in malnourished people and in untreated (or inadequately treated) patients with type 1 diabetes.
Hemoglobin - The test stripes can find hemoglobin, which is a blood pigment located within erythrocytes. Presence of hemoglobin in the urine may be associated with bleeding into the urinary tract.
pH of urine - The papers can determine whether the urine is acidic or alkaline. Normal urine pH is between 5.0-6.0. Deviations from this value may be associated with urinary tract infections and increased formation of urinary stones.
Urine density - The density of the urine may be stated by the testing papers only approximately. The density means the amount of dissolved substances in the fluid.
2nd Biochemical examination of urine
Basic chemical urinalysis will allow us to better and more accurately determine the presence and quantity of the above-mentioned compounds. In addition, the chemical examination allows to detect other substances and their concentrations including all important ions, urea and creatinine.
3rd Laboratory examination of urine sediment
Urine sediment is obtained when the urine sample is inserted into the centrifuge, and the solid parts are investigated under the microscope. The result is fairly quickly available and helps us to find a number of substances.
Red blood cells - The presence of red blood cells visible by the microscope clearly confirms blood in urine. The examiner can detect their numbers in the field of view and their shape. Deformed red blood cells have been probably filtrated through renal glomeruli, undeformed erythrocytes probably come from the lower parts of the urinary tract.
Bacteria - It is possible to find bacteria in the sediment, but the examination does not say anything about the type of bacteria or their sensitivity to antibiotics. This must be done by microbiological examination of the urine (see below).
Crystals - Small number of crystals occur in the urine normally. The higher incidence may be linked to fluctuations in pH of urine and the formation of urinary stones.
Cylinders - Renal cylinders are protein outflow of renal tubules and they may accompany a wide range of renal diseases.
4th Microbiological examination of urine
This test needs the urine sample to be sent to the microbiological laboratory. When sampling, it is necessary to catch the midstream urine to prevent bacterial contamination. The results are ready in two to three days. The laboratory confirms the presence of bacteria, their number, type and their sensitivity to antibiotics. The mere presence of bacteria in urine does not need to be important, the significant number is more than 100,000 bacteria in 1 ml of urine.
5th Cytological examination of urine
Urine cytology is not performed commonly, but it may be used to diagnose malignant tumors of the urinary tract, especially the bladder cancer. A sample of urine is centrifuged in the laboratory, the present cells are stained and observed under the microscope. It is just an orientational method and its negativity does not rule out the cancer presence.