Protein in Urine
Protein in The Urine
What does protein in urine mean?
"Protein in urine" means high levels of protein in urine. It is a common type of abnormal urine; The other two main types are cloudy urine and blood in urine. The "protein in urine" is not necessarily a sign of illness, as well as happens occasionally in healthy people sometimes. Too much protein in urine is certainly sick, and usually considered to be as an indication of a serious kidney disease. Trace amount of protein in urine is often harmless, but still does not rule out the possibility of a disease if you have a known kidney disease or others (e.g. diabetes) that may affect kidneys.
The protein in urine quantitative test:
- Normal protein levels in urine: ① Total protein in urine <40 mg /24h (fluctuating from 20 to 130mg), upper limit <150 mg /24h; ② Albumin in urine >5mg <30mg /24h.
- High protein in urine: ① Total protein in urine 150mg~1g /24h (mild); ② 1g~3.5g /24h (moderate); ③ >3.5g /24h (Too much protein in urine).
In adults, 24 hours urine output is about 1000-2000 ml (100 ml = 1 dl). The protein in urine qualitative test:
- Negative (urine protein concentration of less than 10 mg /dl);
- Trace (10~20 mg /dl);
- + (30 mg /dl, total protein in urine 300-400 mg /24h, mild);
- + + (100 mg /dl, moderate);
- + + + (300 mg /dl, moderate ~ too much);
- + + + + (urine protein >1000 mg /dl, too much).
Urine color: the "protein in urine" looks like normal urine - light yellow or yellow; Sometime, it is turbid, due to the urine protein precipitation or the formation of protein casts. If the urine contains a lot of protein, the surface of the urine is full of a thick layer of small white foam, which does not go away for a long time. In most cases, urine contains protein, also with red blood cells in urine together. A few red blood cells are not enough to stain urine; However, by a large number, the urine will turn pink or bloody red. If there is a urinary tract infection, urine is cloudy.
Why protein in urine?
The kidneys filter waste products from the blood while retaining useful substances (e.g. proteins, red blood cells, white blood cells, glucose) in the body. In normal condition:
- Only trace amounts of small molecule proteins can be discharged into the urine (These proteins are filtered out from blood, but 95% of them are reabsorbed back into the blood within the kidneys);
- Trace amounts of albumin (medium-molecular protein, the largest proportion of protein in blood) can be present in the urine (5~30mg /24h);
- The macromolecular immune proteins will never be present in the urine.
However, a number of diseases can destroy the kidney's filtration system and re-absorption system. Thus, a high amount of protein and macromolecular proteins can pass through the filters of your kidneys into the urine: For example, the filters of the kidneys being inflamed (e.g. glomerulonephritis) or being destroyed (e.g. in diabetic patients); Or simultaneously, accompanied by the elevated concentration of protein in the blood. As a result, proteins are expelled, and there is an abnormally high protein in urine.
What causes protein in urine?
Protein in urine is a result of kidney disease that damages the renal glomeruli (filtration system, tiny cluster of capillaries, responsible for filtering) and the renal tubules (re-absorption system, reabsorbing urine into the blood, also collecting and conducting the remaining urine into renal calyx and pelvis, and then into the ureter, bladder).
These kidney diseases can be divided into three types: glomerular disease, tubular disease, renal vascular disease. Among them, glomerulonephritis is the leading cause of protein in urine. There are also many other diseases that can cause cloudy urine. For example, kidney infection (pyelonephritis), diabetes, high blood pressure, allergic purpura, systemic lupus erythematosus, HBV, myeloma and lymphoma, all of them can cause kidney disease when in advanced stage. Thus, proteins are filtered out from blood, then present in urine. Sometimes, a slightly elevated protein in urine can be harmless; The trigger factors include:
- Great physical exertion, sport activities;
- Intake of protein-rich food;
- Exposure to excessively low temperature or too high temperature;
- Having a fever;
- Emotional stress;
- During pregnancy.
Protein in urine symptoms
"Protein in urine" reveals a kidney disease problem. When you have an abnormally elevated protein in urine, you may have symptoms due to protein loss, also suffer from symptoms of kidney disease.
- Blood in urine: red blood cells in urine (microscopic, can not be found by the naked eye), or blood-red urine (macroscopic, can be seen by the naked eye).
- Patients may have anemia.
- Protein in the urine.
- Diminished urine production and excretion.
- Edema: mild edema affecting eyes in the morning (puffy eyelids), further swelling of the legs, severe edema throughout the body and weight gain.
- Hypertension: Renal glomerular disease is often accompanied by high blood pressure.
- Too much protein in urine and thus blood-protein loss: leading to hypoproteinemia (low levels of total protein in blood), edema and hyperlipidemia (an excess of lipids in the blood).
- Fatigue and body weight gain.
- Impaired renal function or even renal failure in the end stage.
When to see a doctor
If you have discomfort or persistent edema, blood in urine, or a large number of foamy urine, you should consult your doctor. If the urine test strips have revealed the "protein in urine", you should ask your doctor whether you need a further urine test. Protein in urine can be temporary, harmless, or diseased, so your doctor may recommend that you test your urine again as first thing in the next morning or a few days later. Your doctor will further test your urine protein (quantitative test: 24-hour protein in urine or specific urine protein test).
About the treatment, you should consult your doctor. Treatments of protein in urine depend on the underlying cause, for example:
- Control of the inflammatory diseases, infections, blood pressure;
- Application of glucocorticoid;
- Diuretic therapy against edema;
- Low-salt diet and control of protein intake;
- Having a lot of rest; and so on.
Last update: 2012-10-16