What's the matter with weak positive urine protein found in physical examination

People's normal urine contains trace amounts of protein, and a small amount of protein is within the normal range. If during a physical examination, the doctor tells you that your urine protein is weakly positive, this is an abnormal result. Based on the weakly positive protein content, it is determined whether there is a physical illness. It also does not rule out the possibility that the person has taken medicine before the examination, has had an illness recently, or has had a urine test on a pregnant woman.

Overview

Normal urine contains trace amounts of protein (24-hour urine protein quantity <150 mg), which cannot be detected by ordinary detection methods and the test result is negative. If the amount exceeds this range, it can be detected and is called proteinuria. Many people also test weakly positive for urine protein during physical examinations.

A weak positive urine protein result is considered normal. Generally, a normal person filters up to 180 liters of original urine every day, but only about 1.5 liters are reabsorbed, secreted, and finally concentrated and excreted by the renal tubules. It contains about 40 to 100 mg of protein, which cannot be measured using the urine protein qualitative method.

The urine protein commonly referred to is not always pathological. It can be divided into functional urine protein and weakly positive pathological urine protein. Functional urine protein, also known as physiological urine protein, refers to temporary urine protein that appears in healthy people. It is more common in young people. Under the influence of factors such as strenuous exercise, fever, high temperature, cold, and mental stress, the renal blood vessels spasm or congestion, resulting in increased permeability of the glomerular filtration membrane and a large amount of protein "leaking through".

Some normal pregnant women may also have a slight increase in protein in their urine, which is related to increased body position, renal flow, and glomerular filtration rate. Functional urine protein will disappear on its own once the cause is eliminated. Therefore, it is also called reversible urine protein or transient weak positive urine protein.

If you want to know whether there is protein in the urine and how much protein there is, there is a simple and rough test method, namely: boil the urine for a while, white turbidity may appear in the urine, add 5 to 10 drops of 5% acetic acid and boil it again. If the turbidity disappears, it means that there is no protein in the urine and the urine protein qualitative test is negative; but if the turbidity does not disappear but increases, and appears as flocculent precipitation or clots, then the urine protein is weakly positive.

Common Situations

The pathological urine protein that people are most concerned about is that it refers to the continuous presence of protein in the urine caused by a lesion in a certain system or organ of the human body. Generally, the amount of urine protein in 24 hours exceeds 150 mg. [1] Weak positive urine protein is commonly seen in the following three situations:

1. Weakly positive glomerular urine protein: Damage to the glomerular capillary wall due to various reasons (such as immune damage) reduces or loses the load, leading to increased glomerular permeability. After more plasma proteins are filtered, they exceed the reabsorption capacity of the renal tubules, resulting in urine protein. Such as acute and chronic nephritis, lupus nephropathy, diabetic nephropathy, etc.

2. Weakly positive tubular urine protein: When the renal tubules are diseased or the tubular function is defective, protein reabsorption is reduced or protein secretion is increased, resulting in increased urine protein. Such as renal tubular acidosis, nephropathy caused by analgesics, and nephrotoxic manifestations of antibiotics.

3. Weakly positive overflow urine protein (also known as coagulated urine protein): The patient's urine becomes turbid when heated to 40°C, coagulates at 60°C, and dissolves at 100°C. It is seen in multiple myeloma, primary amyloidosis, macroglobulinemia, etc.