Protein in the urine (proteinuria): when to worry?

Proteinuria is the presence or urine protein level. Research and determination of protein in urine informs about the proper functioning of the kidneys. If the increase in proteinuria lasts over time, it may reveal a disease. What is proteinuria? What are the normal values? What are the causes ? when to worry proteinuria during pregnancy? What to do ?

Definition: what is proteinuria?

“Proteinuria corresponds to the presence of proteins in the urine. Most often it is a protein called albumin“, explains Dr. Aurélien Lorthioir, nephrologist at the European Georges Pompidou Hospital. Research and protein dosage in the urine provides information on the proper functioning of the kidneys. However, the increase in protein levels in the urine is not necessarily dangerous. Indeed, it can be temporary, for example after an intense effort. It is when it is permanent that you really have to pay attention to it, because it can reveal kidney damage.

What are the normal values ​​for proteinuria?

Normally, urine should contain little protein since the kidneys are responsible for filtering it. “Physiological proteinuria [soit la quantité normale de protéine dans les urines] is very low: 100 to 150 mg per day. Under physiological conditions, albuminuria can be observed [présence d’albumine] around 15 to 30 mg/day“, he specifies.

What causes proteinuria?

“The causes of proteinuria are multiple. Depending on whether it is transient or permanent, on the abundance and type of proteinuria, on the existence of other abnormalities (hypertension, edema, presence of white blood cells or red blood cells in the urine, etc.), proteinuria can be part of a mild or serious health problem.“, confirms Dr. Lorthioir. For example, the presence of Bence Jones protein in the urine contributes to the diagnosis of multiple myeloma. In children, it is also worth mentioning orthostatic proteinuria which is characterized by proteinuria present only when urinating standing up (and not in a sitting position). This phenomenon, whose origin is still unknown today, disappears around the age of 20. Orthostatic proteinuria is therefore not a symptom of a particular disease.

When to worry about proteinuria during pregnancy?

During pregnancy, proteinuria is usually checked monthly via a urine test. When the levels are normal, they provide information on the good progress of the pregnancy. “Most often, the appearance of proteinuria during pregnancy, combined with the appearance of arterial hypertension, fears the diagnosis of pre-eclampsia which is a serious complication of pregnancy and requires urgent and specialized care“, specifies Dr. Aurélien Lorthioir. When it is not taken care of in time, pre-eclampsia (formerly called toxemia of pregnancy) can evolve towardseclampsiawhich is manifested by the appearance of convulsions and constitutes a life-threatening emergency for the unborn child and for the mother.

What test to do for proteinuria?

There are no symptoms in isolated proteinuria. “To detect proteinuria, you need to do a urinary test“, assures the specialist. The easiest way is to use a urine dipstick then, if the result is positive, to measure proteinuria on a urine sample in a laboratory. “If the proteinuria is weak, one can ask the microalbuminuria assay to search for very small amounts of albumin“, recalls the expert. To quantify proteinuria, the classic method consists in doing a urine collection for 24 hours and gives a proteinuria result in grams or milligrams per 24 hours. The 24-hour urine collection is restrictive and for several years, it has been replaced by a sample collection with measurement of proteinuria, creatinineuria and calculation of the proteinuria to creatinine ratio which allows a good estimate of proteinuria.

► Cytobacteriological examination of urine (ECBU) is prescribed by the doctor to diagnose a urinary tract infection (cystitis, pyelonephritis, prostatitis…). In women, UTIs are usually manifested by pain during urination, burning, blood in the urine, frequent urination, chills, and fever. Similar symptoms characterize a urinary tract infection in men, with occasional pain in the testicles as well as a discharge of fluid from the urethra.

What to do in case of protein in the urine?

In case of protein in the urine, even if it is low, it is better to consult your doctor who will complete the assessment and refer the patient to a nephrologist if necessary. Then, “must be systematically carried out a cytobacteriological examination of urine (ECBU)looking for a urinary tract infection and/or looking for an increase in white blood cells or red blood cells in the urine, which may point to kidney disease“. The ECBU makes it possible to carry out a cytological and bacteriological analysis from a urine sample of the first urination in the morning. It determines the count of red blood cells and leukocytes, the presence of crystals and germs. In accordance with the indications given on your analysis sheet, the results must be the following on average: less than 10,000 leucocytes/mL, less than 10,000 red blood cells/mL and an absence of germs.

► One increased white blood cell count may be seen in patients with urinary tract infection or in certain cases of kidney disease (for example in the case of sarcoidosis or in the event of an allergy to certain drugs). The number red blood cells may increase with urinary tract infection but may also be a sign of kidney disease.

What does proteinuria mean in diabetes?

“In case of diabetes, the urine is regularly checked for the appearance of proteins, even in very small quantities. This is called the microalbuminuria“, continues the specialist in nephrology. In a diabetic patient, the appearance of micro albuminuria most often means that the kidneys have been damaged by diabetes. It is one of the first stages of the diabetic nephropathy. At this stage, there is no renal failure. To avoid kidney failure, “certain treatments (called renin-angiotensin system blockers) are given to diabetic patients with microalbuminuria as this can lower the amount of albumin in the urine and protect the kidneys in the long term“, concludes the expert.

Thanks to Dr Aurélien Lorthioir, nephrologist at the European Georges Pompidou Hospital.