What is it about ?
Urinalysis is used to detect a urinary tract infection (urethra, bladder, kidneys) or kidney disease or to aid in the diagnosis of diseases that affect the whole body (systemic) such as diabetes.
A urinalysis can be done in different ways:
- by dipping a test strip or test strip in the urine. The color of the strip is then compared to a standard strip. The coloring provides information on the degree of acidity (pH), on chemical modifications (presence of sugar, nitrites, proteins, etc.) and on the presence of red blood cells and white blood cells.
- by examining, under a microscope, urine that has been centrifuged for 5 minutes in a test tube. Centrifugation precipitates all cells and other urine components at the bottom of the tube. This precipitate is then examined under a microscope.
- culture of bacteria present in urine is only useful if there is suspicion of infection. The bacteria are grown in a special culture medium and identified in the laboratory. The effectiveness of the antibiotics against the germs detected is then tested.
- cytological analysis examines the malignant nature of cells found in urine.
Your doctor will decide which test is best for you based on your symptoms. In principle, it always starts with a test strip and a microscopic examination.
Which urinalysis does the doctor use for which condition?
Urinary tract infections
If you are a healthy woman, are not pregnant, have had cystitis in the past and clearly recognize the symptoms, microscopic analysis is not necessary. In all other cases, if kidney or bladder infection is suspected, the doctor will perform a urine test by dipstick and microscopic examination. He will carry out a bacterial culture in addition:
- in case of fever,
- in the event of persistent complaints,
- if you develop a bladder infection when you are already taking medicine to prevent it,
- if there are signs of an ascending infection (an infection that goes up to the kidneys)
- in certain risk groups: children under 12, men, pregnant women, people with diabetes, immunodeficiency, urinary tract or kidney abnormalities or bladder problems (due to an innervation problem or a catheter). This is because risk groups are more vulnerable to urinary tract infections.
Detection of renal abnormalities
The most common way to detect kidney abnormalities is to examine the urine with a test strip and under a microscope. If we only find red blood cells in urine, without signs of infection, this may suggest a disease affecting the whole body (a systemic disease) (eg increased tendency to bleed), kidney disease or lower urinary tract disease (eg . from kidney stones or cancer), but it could just as well be a sign that you are exerting intense physical effort (e.g. if you play endurance sport) or that you are having your period.
Detection of other diseases
To detect other diseases, the doctor will target the urinalysis on the following:
- presence of protein in urine : Small amounts of albumin (a protein) may indicate diabetes or kidney damage from high blood pressure.
- the presence of sugar in the urine can suggest diabetes. In this case, the level of sugar in the blood (blood sugar) is also controlled.
- the presence of ketone bodies in the urine: these are chemicals that the body produces when there is a sugar deficiency; this result may indicate poorly controlled diabetes.
- the degree of acidity (pH) of the urine, which can influence the formation of kidney stones and the elimination of drugs from the body.
How to properly collect a urine sample?
It is very important to take a urine sample correctly. A sample taken in poor conditions entails a high risk of contamination by other bacteria; the sample is therefore not reliable for drawing conclusions. Contamination is suspected as soon as 3 or more different types of bacteria are found in the sample. Therefore, be sure to only use the urine containers provided by the laboratory, doctor or pharmacist. Urine stored at room temperature should be analyzed within 2 hours. It is therefore best to keep your urine in the fridge if you cannot see a doctor within 2 hours.
Adults
It is best to take your urine sample in the morning on an empty stomach or 4 to 6 hours after your last urination. In the morning, drink 1 glass of water; if you drink more, the urine may be too diluted, in which case, even if you have a health problem, the results of the urinalysis may be normal (i.e. negative) (we say that the result is false negative, or that it is a false negative).
Start by washing your hands. Then part your lips or roll up the foreskin. Wash the genitals with clean water or with damp wipes. Dry them with toilet paper. First urinate in the toilet bowl, then in the urine container, then again in the toilet bowl. You thus take the middle of the stream (“mid-stream urine”) and thus minimize the risk of contamination. If the urinalysis is for a sexually transmitted infection, you can urinate first into the urine container and then into the toilet bowl. Close the urine container and store it in the fridge.
Children
Start by giving the child a drink. Wash the lips or penis with a sufficient amount of water (without soap), for example in a bath. In young children, the sample is preferably taken using a pediatric urine bag. Check every 10 minutes, as urine should not stay in the bag for more than an hour.
Transfer the urine to a urine container. The urine taken from the bag is mainly used to rule out bladder infection. For slightly older children, the urine container can be attached to the wall of the child’s container.