What is a urine test and when is it done?

What is a urine test and when is it done?

General description

The urine test is a diagnostic exam that is very frequently used in medicine and which consists in pick up a small amount of urine for be after analyzed at the laboratory. With this test we can acquire information that helps to the diagnosis of usual or urgent pathologies.

The urine test can be divided in two types according to the method of pickup, though in essence they consist in the same type of study:

Basic urinalysis: the urine is picked up when urinating in a bottle, avoiding the first and last jet of urine for avoid the contamination with germs. This type of urine pickup is the most frequent.

24 hours urinalysis: it consists in collect all the urine which is expel during all a day in a bottle. It serves for calculate substances that appear in small amount in the urine.

Urine test with a probe: it consists in collect the urine through a probe which passes through the urethra and arrives to the urinary bladder. It is often done because the patient is already probed, but other times this technique is chosen because just like that the urine is picked up without contaminate directly from the urinary bladder.

Several studies can be done with a urine test: test strip, urine sediment examination, physicochemical analysis and microbiological analysis.

When is a urine test done?

The urinalysis is an exam which is frequently used in medicine because it does not involve great discomfort, is very cheap and can provides a lot of useful information. Because of that it is requested as routine for detect many disease in early stages or cheek their treatment.

The diseases in which a urine test is most requested are: 

The ones that affect the kidney (glomerulonephritis, kidney stones, infections).

It is also requested in systemic diseases cases as mellitus diabetes or autoimmune illnesses: rheumatoid arthritis, systemic lupus erythematous, among other.

It is  also  useful  in  the  detection  of urine´s infections, whether light or severe infections (complicated cystitis or pyelonephritis).

If you are going to have a basic urinalysis, these are the issues that you have to consider for go good prepared to the test:

Duration: it takes a very short time. You can do the pickup of the urine sample at home. It is prefer the first urine of the day and avoid the first jet when urinating. After that you just have to deliver it at doctor´s consultation. 


Hospital admission: it never requests hospital admission. It is a test that can be done on an outpatient basis.


Is company needed? : No


Medicines: take any medications previous the urine test is not necessary. However you must say to the doctor all the medicines that are being taking at that moment. Some drugs can change the normal characteristics of the urine. Many of them are easily related (diuretics, as example), but others can go unnoticed (such as, antibiotics).


Food: usually it is asked that the urine test will be collected after an eight hours fast. That is, just pick up the first urine in the morning having a light and early dinner the night before. 


Clothes: you do not need special clothes for collect or deliver the sample.


Documentation: it is recommended to bring your health card and the test´s indication when you will go to deliver the urine sample.


Pregnancy and lactation: the test can be realized without modify any attitude. It is better if the doctor knows that you are pregnant because the urine can be slightly different.


Contraindications: contraindications do not exist for this test.


How is a urine test done?

You will need a sterile bottle that they will give to you at doctor´s consultation or you will have to buy it at the drug store.

For consider the realization of a urine test, when you arrive at consultation, the doctor will ask you some general questions about your health condition: important diseases, risk factors, life style, work place and above all he will insist on the voiding or urinary symptoms. After, he will realize to you a general physical exploration, and if he decides that is necessary, he will give to you a sheet in the one he solicits the test and where he will point the data that he wants for be analyzed at the laboratory.

Days after this first visit, or at the same moment, you will be able to pick up the sample and take it to the clinic. When you will go to collect the sample it is recommended have your private parts clean for avoid contamination, and it is better that the edges of the bottle do not touch anything. Try to collect the first urine in the morning, because it will be more concentrated and it is more useful for the test. The first jet when urinating is better not collect it because its contamination with germs from the urinary tract is very usual.

What to do once the urine sample is collected?

When you finish collecting the sample close the bottle carefully. Remember that for the analysis a small amount of urine is enough, it is not necessary that you fill it to the top. Leave the bottle at room temperature, but take it to the clinic in the next few hours. If you leave the bottle during many hours in the open air, it can be contaminated with microbes or lose useful substances for the test.

When you arrive to the consultation you will only have to deliver it and you can leave. The results may take from hours to days and they will give them to you at doctor´s consultation. 

Remember that there are not any complications when you realize the urine test. 

Several studies can be done with a urinalysis. Because of that when the doctor delivers to us the results there are many numerical data accompanied with names and acronym which are difficult to understand. The most used exams are:

Test strip: a paper strip is immersed in chemical reactants that react with some substances of the urine. It is the same method that is used for the pregnancy test. Several infections are diagnosed with this test in the primary attention centers because the presence of white blood cells which change the strip´s color. It is a fast method, but less reliable than a laboratory analysis.

Urine sediment examination: there are dissolved solid components in the urine. To study them, the urine is centrifuged and the solids remain at the bottom. They are after studied with the microscope. There can be got data as pH (important in situations of kidney stones that are formed with situations of urine´s acidity), protein presence (in kidney or systemic diseases that affect to the kidney), blood (present in urinary system´s diseases, or in autoimmune diseases), ketone bodies (useful in the diagnosis of complications of diabetes or in prolonged fast), and so on. Also the finding of bacteria or the high count of white blood cells will indicate the presence of infection, especially when the presence of nitrites in the urine will be detectable, which implies that bacterial activity exists.

In pregnancy cases, the presence of beta hCG hormone (beta human chorionic gonadotropin hormone) in urine is determined, though this is usually later than its positivity in blood.

Physicochemical analysis: it consists in the studied of some physical properties of the urine (such as the density) and the chemical components that it has (ions, glucose, and so on). The determination of sodium and potassium provides information about the hydration condition, some adverse effects of diuretic medicines

Microbiological analysis: if an infection is suspected, urine´s bacteria can be searched directly. When there are, the doctor can consider necessary the realization of other diagnostic test, called urine culture. It is also used for the detection of antigens of some microorganisms, such as pneumococcus, that cause pneumonia. 

Determination of toxic substances: this is used for determine if exist urinary elimination of drugs like cocaine, cannabis, or narcotic substances like opiates, benzodiazepines, amphetamines, among other.