What is it about ?
There are a multitude of kinds of proteins present in our blood. If protein is found in the urine, it is called proteinuria.
In a healthy adult, a maximum of 130 mg of protein per 24 hours is excreted in the urine. Albumin is the protein most commonly found in urine. If the amounts of protein found in the urine are greater than normal amounts, we look for the cause.
Proteinuria can be of a transient nature, for example following a fever, an inflammatory disease (a urinary infection for example) or a physical exertion.
If proteinuria persists or if there are also red blood cells in the urine, other causes should be considered: kidney damage due to diabetes, other kidney diseases, systemic diseases (for example amyloidosis), preeclampsia (high blood pressure in pregnant women), side effects of drugs (eg penicillamine, gold complexes), etc.
There is a form of proteinuria where protein is found in the urine only when a person is standing (orthostatic proteinuria).
In whom and how often does it occur?
Orthostatic proteinuria is seen in young people, but it is rare in people over 30 years old.
How to recognize it?
People with diabetes with damaged kidneys have more albumin (a type of protein) in their urine. We therefore regularly monitor proteinuria in them.
Protein is also tested in the urine of pregnant women, as the protein in the urine in them can be a sign that precedes preeclampsia.
In the absence of symptoms or a pattern, it makes no sense to frequently test the urine for protein. However, the absence of protein in the urine does not necessarily mean that you do not have kidney disease.
How is the diagnosis made?
A urine dipstick test allows the doctor to get an idea of the amount of protein in the urine. This strip only detects albumin.
If the test detects too much albumin in the urine, the doctor will look for a condition that may be associated with kidney problems (diabetes, high blood pressure, chronic inflammatory disease, or urinary tract infection). Further tests are only necessary if you have had proteinuria in the past or if there is a reason to suspect kidney disease.
A new strip test is performed, using a new sample of morning urine. If the next two samples are “negative”, ie. that no albumin is detected, it is not necessary to look any further. If albumin is found again in the urine, or even a small amount of red blood cells, additional tests are done:
- Your doctor will ask you the following questions: Has protein been found in the urine in the past? Do you have pain when you urinate? Do you have to urinate more often? Do you have pain in the lower abdomen or sometimes severe pain comparable to colic in the back area? Have you recently had a fever, sore throat, inflammation, or recently made heavy physical exertion? Have you ever suffered or do you suffer from heart or kidney disease, diabetes, rheumatism or do you have urinary tract abnormalities?
- Your doctor will also measure your blood pressure and check for signs of fluid retention (edema). He checks your heart and lungs and checks if your lower abdomen or kidney area is sensitive.
- A blood test
- A collection of your urine for 24 hours. Based on this, the lab will assess the amount of protein secreted in the urine, check how fast the kidneys are filtering blood (estimated glomerular filtration rate or eGFR) or check for signs indicating inflammation, infection or diabetes. .
What can your doctor do?
What your doctor does depends on the lab results.
With more than 0.3 grams of protein in the urine (over 24 hours), but normal creatinine in the blood (a parameter indicating how well the kidneys are filtering the blood):
- proteinuria can be caused by fever or physical exertion. Then, a few days after exercise or a few weeks after recovery from an infection, a new urine test will be carried out on the urine collected for 24 hours.
- in a young and healthy person with a maximum of 1 gram of protein in the urine per 24 hours, the presence of orthostatic proteinuria is tested using tests on the urine excreted at rest (at night). If the amount of protein in the urine is much lower at night, it is most likely benign orthostatic proteinuria.
- after exclusion of orthostatic proteinuria and in the presence of a maximum of 1 gram of protein per 24 hours in the urine, the laboratory performs a specific analysis (protein electrophoresis) to determine the type of protein.
If proteinuria is associated with blood in the urine, further testing is indicated. Other reasons for carrying out additional tests are: high blood pressure, heart problems (heart failure), presence of certain proteins in the urine, proteinuria that is persistent or increases over time.
With more than 1 gram of protein in the urine (over 24 hours), or if there are signs indicating kidney function, you have to find the origin anyway. This is done via an ultrasound of the kidneys and a kidney biopsy in which a piece of tissue is taken from the kidneys to be examined. These examinations are carried out by a kidney specialist (nephrologist).
Want to know more?
- Functional anatomy of the urinary system (images) – microbiologiemedicale.fr
- Location and symptomatology of urinary tract infections (images) – microbiologiemedicale.fr
- Urine test – 24 hour collection – CHU Montreal
- Ultrasound here Where to find on this page of Cliniques St Luc UCL
- The percutaneous biopsy, here, Where to find on this page of Cliniques St Luc UCL
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