The main task of the kidneys is to filter the blood repeatedly and remove harmful wastes, excess water and salt from the body. After the blood in the body is pumped from the left ventricle of the heart, it enters the kidneys through the large arteries called the aorta and the arteries of the kidneys, and is processed to be converted into urine in the filtering units called “nephrons”. The nephron unit consists of a special filter structure called “glomeruli”, which is specialized for the filtration process where the blood is filtered, and a specialized, tubular tubular structure that the filtered blood follows to turn into urine. Each kidney contains about 800000-1000000 nephron units.
While the harmful wastes that need to be removed from the blood are removed through the kidneys, substances necessary for life such as proteins and blood cells in the blood are preserved. There is approximately 7 g of protein in a 100 ml serum portion of blood. In the kidneys, approximately 1200 ml of blood per minute (about 650 ml of which is plasma, which is the liquid part) is filtered and 125 ml of filtrate is obtained per minute. Today too; 180 liters (125 ml/min x 60 minutes x 24 hours) of filtrate means that approximately 99.5% (178.5 liters) of filtrate is reabsorbed as the filtrate passes through the tubular system of the nephrons, considering that the daily urine amount is approximately 1.5 liters. understandable. As can be seen, the kidneys control the amount of fluid excreted in the urine very seriously. Similarly, if it is calculated with a simple calculation from the values given above, it is seen that approximately 65 kg of protein passes through the kidneys daily. Normally, the amount of protein excreted in the daily (24-hour) urine is about 150 mg in adults. This indicates the existence of a very serious protection against protein excretion from the kidneys.
What is proteinuria, how is it defined according to its level? Proteinuria is defined as more than 150 mg of protein excreted in the urine per day. The presence of proteinuria is an important laboratory finding to show that both kidneys are sick. Proteinuria is “significant” when it is between 150-500 mg/day, “significant” when it is between 500-1000 mg/day, “severe” when it is between 1000-3000 mg/day, and “nephrotic” when it is over 3000 mg/day. is mentioned.
Does proteinuria cause signs and symptoms? The presence of proteinuria alone does not cause any signs and symptoms that can be easily noticed by the patient and the physician. However, when proteinuric urine is collected in a container, a careful eye notices that a white foam develops on the surface of the collected urine. On the other hand, in cases that develop swelling in the form of edema in the legs and around the eyes, it is absolutely necessary to look for protein in the urine. Diseases that cause severe or nephrotic proteinuria are usually accompanied by swelling in the form of edema that can be easily noticed by both the patient and the physician. It is difficult to say that this edema is always directly caused by protein lost in the urine. Therefore, it would be more accurate to consider the association of proteinuria and edema as two common findings, rather than as a cause and effect relationship.
Which urine sample shows the presence of proteinuria? Suspicion of proteinuria in daily practice is put forward by visual evaluation of the turbidity that develops by comparing a one-time urine sample (spot urine) at any time of the day with a urine stick for protein or by comparing the centrifuged urine with heating or some chemical substances. This condition, which is defined as spot urine proteinuria, is usually reflected in the urine examination result report as traces, (+), (++), (+++) and (++++) or numerically as mg/dl to reflect the degree of proteinuria. . In order to understand whether this is significant in the name of the disease, the presence and amount of protein in the urine collected for 24 hours is determined from the cases with spot proteinuria and this amount is reported in mg/day. It has been stated that a protein level above 150 mg in the urine collected for 24 hours is abnormal. An important point to be considered here is how to collect 24-hour urine. Patients should learn this seriously and carefully collect even a drop of their urine without losing it, and quickly transport it to a safe laboratory unit where examination will be made. In cases where proteinuria is detected, diagnosed by research, followed up with or without treatment, some physicians monitor the daily proteinuria level by looking at the protein-creatinine ratio in the urine, instead of performing a proteinuria test by collecting 24-hour urine each time.
What are the types of proteinuria? Proteinuria is evaluated in 3 categories as transient, orthostatic and permanent. The most common type of proteinuria is transient proteinuria. The chance of seeing this type of proteinuria is higher in women than in men. It is not a type of proteinuria that requires treatment. The main causes of transient proteinuria are fever and exercise. The characteristic of orthostatic proteinuria is that proteinuria is detected in the urine collected during daily activity, but proteinuria is not found in the urine collected during resting. Although this situation can be seen at a rate of 2-5% in young and young adults, it is not very likely after the age of 30. Its mechanism has not been clearly explained. Orthostatic proteinuria is not a form of proteinuria that requires treatment and disappears with age. Contrary to transient and orthostatic proteinuria, the presence of persistent proteinuria is an important and significant laboratory finding. Kidney diseases, cardiovascular disease, some diseases characterized by abnormal protein production cause a continuous development of proteinuria.
Which physicians should evaluate a case with proteinuria? Cases with proteinuria determined by urine analysis should be evaluated by Nephrology specialists immediately. These physicians listen to the patient’s history, perform a physical examination, and request some other laboratory tests. In cases with daily urinary proteinuria above 1000 mg, even if there is no accompanying finding, kidney needle biopsy is often performed and the condition of the kidney parenchyma is examined histopathologically. Treatment is also arranged according to the determined disease type. In cases presenting with proteinuria values below 1000 mg per day, kidney biopsy can be performed if necessary, taking into account other accompanying findings. If proteinuria cases are not evaluated and treated in a timely manner, they carry serious risks such as kidney failure and dialysis patients, meanwhile, there is a risk of death from intervening complications (such as infection, embolism).
SUMMARY
Normally, no protein is detected in urine analysis. Its presence is defined as proteinuria.
Proteinuria is an important and significant laboratory finding, often without symptoms or signs.
Cases with proteinuria should be evaluated immediately by a Nephrology specialist.
