What is a urine test and when | Medical tests

Analysis of urine 

The urine test is a diagnostic test that is used most often in medicine and consists of collecting a small amount of urine for later analysis in the laboratory. Thank you she can get information that helps in the diagnosis of pathologies regular or urgent.
Types of urine analysis according to the method of collection, although in essence they consist of the same type of study can be divided:
Basic urine test: collect urine at the urinated in a boat, avoiding the first jet of urine and last to avoid contamination from germs. It is the most frequent urine collection type.
24-hour urine test: is to collect all urine that is expelled in a day on a boat. It serves to calculate substances appearing sparingly in the urine.
Analysis of urine with probe: it's collecting urine through a tube that passes through the urethra and the bladder reaches. Many times it is made this way because the patient is already probed, but others choose to this technique because this results in urine without contamination from the bladder directly.
Multiple studies can be performed within urine test: Test Strip, sediment from urine, physico-chemical analysis or microbiological analysis. In the section on results we will see in what consist and what indicate data that we provide.

When a urine test is done

The urine test is a test that is very frequently used in medicine because it involves no great inconvenience to do so, is very inexpensive and can provide lots of useful information. Why it calls routine to detect many diseases in early stages or control their treatment.
Diseases that more calls for a urine test are those that affect the kidney (Glomerulonephritis, urinary calculi, etc.). But it also calls in systemic diseases such as diabetes mellitus or autoimmune diseases (rheumatoid arthritis, lupus...). It is useful, in addition, in the detection of urine infections, whether mild or severe infections (cystitis or pyelonephritis complicated).

Preparation for urinalysis

If you are performing a basic urinalysis these are issues you must keep in mind to go well prepared to test:
Duration: lasts a very short time. You can make the urine sample collection at home. Preferred urine first thing in the morning and avoid the first jet to the urination. Then you will only have to dispose of it at the doctor.
Admission: admission is never needed. It is a test that can be done on an outpatient basis.
Is it necessary to be accompanied?: no.
Drugs: don't need to take any medication prior to the urine test. Although we must say to the doctor all medications you are taking at that time. Some drugs can alter the normal characteristics of the urine. Many of them are easy to relate (diuretics, for example), but others may go unnoticed (e.g. antibiotics).
Food: usually calls for the urine sample is collected after an eight-hour fast. I.e. simply collect urine first thing in the morning having dined early and light the night before.
Clothes: you don't need special clothes or to collect the sample or to deliver it.
Documents: it is advisable to carry your health insurance card and the wheel of proof when you go to give the sample of urine.
Pregnancy and breast-feeding: the test can be taken without modifying any attitude. It is better that the doctor knows you are pregnant because the urine may be slightly different.
Contraindications: there are no contraindications for this test.

How a urine test

When you get to the consultation the doctor will make you some general questions about your state of health: important diseases, risk factors, lifestyle, work place and mostly insist on Voiding or urinary symptoms. After perform you a general physical examination, and assess the realization of a urine test. It will give you a flyer which asks the test and designated data wanting tested in the laboratory.
Days after this first visit, or at the same time, can collect the sample and take her to the clinic. You will need a sterile rubber boat that will give you at the doctor or have to buy at the pharmacy. When you go to collect the sample it is recommended to keep your private parts clean to avoid contamination, and is better do not touch the edges of the pot with nothing. It seeks to collect the urine in the first hour of the morning, it will be more concentrated and is most useful for analysis. The first jet of urine to the urination is better not pick it up because it is normal that it is contaminated with bacteria from the urinary tract.
When you are done collecting the specimen close the pot carefully. Recalls that you for enough analysis with low volume of urine, it does not need to fill it to the maximum. Leave the boat at room temperature, but take it to the clinic in the next hours. If you leave the boat for many hours outdoors can contaminate of microbes or lose substances useful for analysis.
When you reach the consultation only, you may deliver it and you can go. The results can take anywhere from hours to days and will give them to you in the doctor.
There are no complications when done a urine test.

Results of the analysis of urine

Multiple studies can be performed in the analysis of urine. So when the doctor gives us urine results there are many numerical data accompanied by names and acronyms which are difficult to understand. The tests most commonly used are:
• Test strip: is immersed a strip of paper with reagents and chemicals that react with certain substances that can be in the urine. It is the same method that is used to test for pregnancy.
• Urine sediment: there are solid components dissolved in the urine. To study them, centrifuged urine and solids remain in the background. They are then studied under a microscope.
• Physico-chemical analysis: consists in the study of certain physical properties of the urine (such as density) and the chemical constituents that therein (ions, glucose, etc).
• Microbiological analysis: If an infection is suspected can be searched directly bacteria in the urine. When the doctor any other diagnostic test called urine culture you may consider necessary.
Then we will see in more detail how to decrypt the results that provide us with each of these specific studies of the urine.

Reagent Strip

This method, the test strip, is the same that is used to confirm the existence of a pregnancy. It consists of a strip of paper impregnated with reagents and chemicals that enters the urine and throws us to the following possible data and results:


It is the measure that is used to measure the acidity of the urine. One pH less than 7 is considered low and therefore acid, one pH greater than 7 is considered high and indicates that the substance is Basic. Urine usually has a pH that ranges between 4.5 and 7.5, i.e., it is slightly acid.
clip_image001less than 4.5 pH: indicates that there is an excess of acidic substances in the body and that they are throwing out. This usually happens in severe infections or diabetes mellitus not controlled.
clip_image001[1]pH greater than 7.5: mainly happens when the kidneys are not able to eliminate acidic blood substances, so they accumulate and produce metabolic alterations. This happens in renal failure.

Ketone bodies

When the human body cannot produce energy through glucose and other sugars begins to burn fatty acids in an uncontrolled manner. This leads to the production of substances called ketones, which appear in lengthy fasts and diabetes Decompensated. Normal is that the urine does not exist, and when there is an altered sample. Its seriousness and importance according to the concentration of ketones is classified:
  • Minor: 20 mg/dL.
  • Moderate: 30 - 40 mg/dL.
  • Grave: 80 mg/dL.


There are waste substances whose main component is (e.g., urea) nitrogen in urine. When there are bacteria in the urine, by an infection, they can use those compounds to feed, so they transform nitrates into nitrites. Therefore the presence of nitrites in the urine geared towards an active infection.


The human chorionic gonadotropin (HCG) is a hormone whose presence in the urine is used to make the diagnosis of pregnancy. It appears in the blood in the first weeks of pregnancy since it is synthesized by the placenta. It has effects on various organs of the body and its function is to prepare the body of the woman for pregnancy.

Urinary sediment

In the laboratory it can centrifuge urine sample, leaving solid sediments at the bottom that after study under a microscope they provide us these data, whose presence or alterations may indicate various medical problems:


Usually proteins do not appear in urine because they are molecules too large to filter in the kidney. If they appear we can divide this finding:
Hyaline protein: can be considered normal the appearance of hyaline protein in moderate amount. This type of protein synthesizes them own kidney and does not indicate disease. When appear in excess may be due to a global damage of the kidney (a tubular necrosis acute, for example).
Microalbuminuria: the presence of albumin in the urine is always pathologic. When they are between 30 - 300 mg/dL is considered that there is a slight kidney damage. It is a very important fact in diabetes mellitus, and is a must start with medical treatment to correct this alteration. The presence of microalbuminuria is a vicious circle, because it damages the kidney itself.
Proteinuria: 300 mg/dL over talk about Frank proteinuria. Kidney damage is severe and sometimes treatment can only slow the disease. It sometimes occurs in the context of specific diseases that disappear in time, such as nephrotic syndrome.

Red blood cells

The presence of red blood cells or red blood cells in the urine indicates that something is not going well. Red blood cells are cells large enough to pass through the filter of the kidney in health conditions. They point to damage in the kidney (nephritic syndrome, for example) or in the urinary tract (spreadsheet that damaged the wall of ureters, or bladder tumors, for example). We can divide this finding:
  • Microhematuria: when the urine is to simple view is not tinged with blood, but to see it under a microscope red blood cells are observed floating indicating a slight bleeding.
  • Macrohematuria: in this case the urine is now tinged with blood and you can see even as is urine. When bleeding is not very abundant said that urine comes out in 'water washing meat', i.e. with dirty and reddish appearance.
  • Urinary tract hemorrhage: bleeding through the urinary tract is so that it does not seem to urine. Under the microscope are observed as many cells as in a direct blood sample.

White blood cells

The presence of leukocytes or white blood cells in the urine is always pathologic. The most frequent is to indicate that white blood cells of our immune system going into the urinary tract to resolve an infection. They can be also seen in renal, colic because impacted stone can cause local inflammation.


Inside white blood cells, there is a special group called eosinophils. These cells are activated to allergic pictures or parasites. Its presence in the urine geared towards a picture of these features (for example, interstitial nephritis by an allergy to drugs).


It is normal to find some bacteria in the urine in isolation, most by contamination of the collected urine sample. A Gram stain, which consists of stained bacteria for observing them under the microscope and try to determine its origin must be in the presence of bacteria in the urine. If it is believed that bacteria may be causing an infection, a urine culture should be done to see which species is in particular.


There are substances dissolved into particles in urine. Sometimes these particles precipitate and form larger crystals that can be observed in the microscope. Some of these crystals appear naturally in the urine, others point to alterations of the kidney or the composition of urine. PH plays a fundamental role for the prevention of the formation of this type of crystals. The most common crystals are:
  • Uric acid: hyperuricemia is cause frequent of crystals in the urine, often accompanied by drop.
  • Cystine: the presence of these crystals is called Cystinuria, and it may be the first symptom of alterations in the metabolism of amino acids.
  • Calcium oxalate: along with calcium phosphate with the two types of crystals in which calcium has a major role. Artichokes favour the emergence of these crystals, which in principle do not indicate abnormalities of the urinary system.

Physico-chemical analysis of urine

The detailed analysis of some physical properties of (volume, density, colour, appearance, smell) urine and chemical components containing allows you to diagnose some illnesses:

Color and appearance

Although it may seem too simple, direct urine sample display can give valuable information for diagnosis and also to guide the laboratory analysis. The color indicates which type of substances may also be dissolved in the urine, the most characteristic are:
· Color wine, cognac or cocacola: indicates the presence of bilirubin in excess in the urine.
· Pink flashing: indicates the presence of moderate bleeding, "water washing meat".
· Orange: appears when certain drugs are taken as rifampicin.
· Whitish: indicates presence of pus in the urine, pyuria is called.


The normal range of glucose in urine is 0-0, 8 mmol/L (0 - 15 mg/dL). That is, typically don't have glucose in the urine or have very little. Glucose is very small and Yes seeps into the kidney, but then reabsorbs nearly everything because it is a basic element for obtaining energy by our body. The presence of glucose in urine means that the amount of blood sugar is so high that kidney can not absorb everything and eliminates it. This occurs mainly in diabetes mellitus.

Bilirubin and urobilinogeno

Bilirubin and urobilinogen are synthesized in the liver and hence most passed to the digestive tract, although a small percentage of conjugated bilirubin passes into the blood and is removed by the kidneys. It is responsible for the yellowish color of the urine. When, for some reason, bilirubin cannot be deleted into the digestive tract (for example, a gallstone) the amount that passes into the blood is greater and urine stains from a more intense, even brown color.


The urine density is mass per unit volume that. Their normal values are between 1000-1030. It is an indirect way of measuring the concentration of particles that are dissolved.
  • Less than 1000: means that the urine is very dilute and concentration of particles is very low. It happens when the kidney removes more water than normal, as when we take diuretics, we are suffering from diabetes mellitus or diabetes insipidus.
  • More than 1030: urine has many concentrated substances. It often occurs in situations of dehydration, when the kidney reabsorbs water and urine appears more concentrated.


It is a more accurate way of measuring the concentration of solutes in the urine. Normal values vary from 50-1200 mOsm/kg. It is really useful when we carry out comparative analyses in time after changes in water intake. I.e., if we are for a few hours without drinking water, the kidney should absorb it, urine would be more concentrated and its higher osmolality. On the contrary, if we drink a lot of water in a short space of time, kidney does not absorb water, the urine would be more diluted and its lower osmolality.


Sodium is found naturally in the urine, it is indeed the most important element in all organic secretions. Normal values are 40-220 mEq/L/day. Retention by the kidney, and therefore water regulation of body hydration, uses it sodium is a mineral that captures water.
  • Less than 40: kidney is re-absorbing sodium (and thus water) and therefore appears diminished in the urine. It happens in situations of dehydration, but also diseases like heart failure where the mechanism of water retention is altered.
  • More than 220: the kidney removes sodium and there is too much in the urine. The most frequent cause is the treatment with diuretics.
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