The urine examination is one of the most common examinations in internal medicine and a simple, non-invasive method to gain information about pathological processes in the kidneys and efferent urinary tracts such as the bladder or urethra. It can also possibly provide information about systemic diseases. The simplest urine test is the urine test strip, which is held in the middle stream urine and indicates the presence of certain substances such as ketones, nitrite, proteins, inflammatory cells, sugar, pH, blood and bilirubin by discoloring test fields. In addition, urine cultures for the detection of bacteria and the so-called urine sediment, a urinalysis for solid and cellular components in urine, can be performed.
For whom is a urine examination necessary?
A urine examination is needed to detect pathologies in the urinary tract and kidneys. Patients who have pain while urinating or in the flank should have a urine examination done by a doctor. This is especially important in cases of bacterial infection.
If there is blood in the urine or foaming urine, a urinalysis should also be performed. The causes of blood in the urine include a urinary tract infection and inflammation of various structures of the kidney, such as the renal calices or renal pelvis. Also, if water deposits (edema) form on the body, a urinalysis is useful to detect proteins lost with the urine. Patients with diabetes mellitus can show increased sugar levels in the urine, and pregnant women are often given a urine test.
How old may the urine be?
Like any other examination, the urine examination is prone to errors. Values and results can be falsified by errors in the performance or measurement. In general, the fresher the better.
However, the shelf life of the sample depends on the type of urine analysis. If the physician wants to create a urine sediment, it is recommended that the urine should not be older than 2 hours before centrifugation. Urine for test strip testing is best used fresh, within 1-3 hours at most.
Many of the values will be falsified if the test strip is left standing for a longer period of time, as metabolic and degradation processes in the urine continue and render the sample unusable. The urine should also be as fresh as possible for cultural cultivation of bacteria. So if you are invited to a urine analysis, it is advisable to hand in your urine fresh at the practice or to collect it shortly before you arrive at the doctor’s, otherwise you may be asked to go to the toilet again. This topic might also be of interest to you: Why is urine yellow?