What is proteinuria?

Proteinuria is the presence of abnormal quantities of protein in the urine, which may indicate damage to the kidneys.

Proteinuria [Pro-teen-yur-ee-uh] is the loss of protein from the blood that can impact your overall health. If your body loses excessive protein when you urinate you are at higher risk for developing possible chronic kidney disease. When this happens, doctors and medical professionals label this condition as Proteinuria. As kidney function decreases, larger amounts of proteins can spill into the urine. Healthy kidneys will only allow fluid and small molecules into the urine. When there is excessive protein is in the urine, it may be a warning sign of kidney damage. However, a laboratory test is required to know what is causing the changes in your urine.

When healthy kidneys filter fluid, minerals and wastes from the blood, they usually do not allow large amounts of serum protein to escape into the urine. But when kidneys aren’t filtering properly, proteinuria can occur, meaning that an abnormal amount of protein is present in the urine.

The two major groups of serum proteins in the blood are albumin and globulins. Albumin is abundant in the blood, accounting for more than 50 percent of all serum proteins. Its important functions include pulling water into capillaries and maintaining the right amount of water in the circulatory system, as well as binding and carrying substances that are poorly soluble in water. Three examples of these substances are fat soluble vitamins, calcium and some medications.

Globulins are divided into alpha, beta and gamma globulins. Alpha and beta globulins also transport substances, while gamma globulins are known as immunoglobulins or antibodies. Testing for protein in the urine can include all the different proteins or albumin only.

Types of proteinuria

Transient proteinuria is the temporary excretion of protein and can be caused by strenuous exercise, a high fever, exposure to cold, stress and other conditions. Pregnant women may also excrete more protein in their urine. Transient proteinuria does not involve underlying kidney disease and requires no treatment. Those who have intermittent or periodic protein in the urine,this may occur during pregnancy or even after strenuous exercise. It is not usually suggestive of kidney disease. If you have a urine lab test that shows greater than 150mg of protein, you should have it tested again to see if it is transient and talk with your doctor.

Orthostatic proteinuria means an increased amount of protein is excreted when a person is in the upright position. It’s most often found in tall, thin adolescents and young adults less than 30 years of age. The kidneys are usually healthy. People who only have proteins in the urine when they are standing or sitting is also known as Postural Proteinuria. They do not have the problem when they are lying down. This is not a condition that is caused by kidney disease.

Proteinuria can be caused by diseases not involving the kidneys, such as multiple myeloma, a cancer of the plasma cells in the bone marrow. In this case, the blood is flooded with too many proteins that are then filtered into the urine. The condition is known as overflow proteinuria. This is the most serious type of proteinuria. If you have more than one test showing high levels of protein in your urine, you should talk with your doctor immediately.

The other type of proteinuria is due to kidney disease, such as glomerulonephritis, primary focal segmental glomerulosclerosis (FSGS) or kidney damage due to a systemic disease. Microalbuminuria means low levels of albumin are detected in the urine. Microalbuminuria can indicate that people with diabetes or hypertension are developing early stages of kidney disease.

Symptoms of proteinuria

In most cases, mild to moderate proteinuria does not precipitate symptoms and many patients may be diagnosed with proteinuria by way of a routine testing to evaluate general health or conditions such as hypertension or diabetes.

Some patients may notice that their urine is more frothy than usual and more severe cases may be associated with edema, ascites, hydroceles and pleural effusions.

In most cases, proteinuria has no symptoms and is detected during a routine screening in people with high blood pressure or diabetes. If protein loss is severe, swelling or edema can occur.

  • Face and around the eyes
  • Arms, hands, legs, ankles and feet
  • Abdomen

A UACR more than 30 mg/g can be a sign of kidney disease. When your kidney damage gets worse and large amounts of protein escape through your urine, you may notice the following symptoms: Foamy, frothy or bubbly-looking urine when you use the toilet. Swelling in your hands, feet, abdomen or face.

Other symptoms can include:

  • Foamy urine
  • Weight gain caused by fluid retention
  • Diminished appetite
  • Hypertension


Foamy urine

If you’re starting to lose a lot of protein from your body, you might start experiencing this symptom. You’ll notice that your urine has a frothy or foamy appearance. Usually, this symptom comes with edema or swelling. This is because there’s an excess of water in the tissues of your body.

There’s no immediate treatment for this symptom. If you notice that you’re peeing out foamy urine, it’s best to seek medical advice. Your doctor is the best person to give you the proper treatment for proteinuria.


Rapid weight gain

Another possible symptom of proteinuria is rapid weight gain. Usually, fluid retention causes this weight gain. Again, this results from the kidneys not functioning properly. If you notice this symptom and you don’t see any reason for it, you may have this condition.If you’re gaining weight because of fluid retention, you need to make some changes. First off, you should start reducing the amount of salt in your diet. Doctors may also recommend that you restrict your protein intake too. Another treatment would be to take water tablets. These are diuretic medications which aid in the elimination of water from the body.


Chronic fatigue

Chronic fatigue is different from just feeling tired. Here, you feel drained, and you may have some problems concentrating. This is a symptom of proteinuria as it may stem from the loss of your kidney’s functions. Toxins start to build-up in your body, and your blood becomes impure. Because of this, you start experiencing chronic fatigue.

If you’re feeling weak and tired, the best way to remedy that is to get some rest. If the fatigue comes suddenly and frequently, then you should visit your doctor. You won’t be able to treat chronic fatigue correctly unless you know what exactly causes it.

How is proteinuria diagnosed?

Proteinuria is common in the adult population and its clinical significance can vary widely. A clear diagnostic process is needed to identify the cause of the findings and guide the treatment decisions.

A dipstick test is often the first indicator of proteinuria and the extent of protein in the urine can be further investigated with a 24-hour urine collection test. If the results are positive, other diagnostic tests may be required to establish the cause of proteinuria and aid in the management of the condition. Referral to a nephrologist may also be needed in some cases.


Dipstick Test

The urine dipstick test can be used as an initial indicator of the presence of protein in the urine and renal disease as it is a simple and easy test to conduct. It involves a single urine sample, which is immediately analyzed for the presence of certain substances (including protein such as albumin) that may be indicative of renal disease.

As many as 17% of the adult population will have positive findings from the dipstick test, but less than 2% will have a condition that requires treatment.

Given the high rate of false positives, if mild to moderate proteinuria is detected with a dipstick test, the test may be repeated in 2-3 weeks to monitor the protein concentration. If severe proteinuria is detected, or a second test proves to be positive, further diagnostic testing is required.


24-Hour Urine Collection Test

Proteinuria is usually diagnosed by measuring the quantity of protein in urinary excretion in a 24-hour period. This test involves the collection of all urine excrete over a complete day, which is then analyzed for the quantity of protein.

Although the testing period can begin at any time, most patients start in the morning. The bladder should be emptied completed at the beginning of the time (with no sample taken) and from that point, the urine should be collected in containers every time the individual goes to the toilet. This continues until exactly 24-hours after the start time, when the final sample should be taken.

It is important that the urine samples are kept in a cool place such as the refrigerator until the conclusion of the collection period, when they should be sent to a laboratory for testing.

In otherwise healthy people, the excretion of more than 500-1000 mg of protein in a 24-hour period may be indicative an abnormality in the function of the kidneys. This may warrant further investigation, such as a blood analysis or kidney biopsy. If more than 2 g of protein is excreted within 24 hours, the patient is likely to have glomerular malfunction.

Urinalysis covers a number of tests performed on urine. Abnormal presence of cells and urinary casts, tiny tube-shaped particles, may reveal underlying kidney disease.The Urine Albumin to Creatinine Ratio (UACR) is a test that estimates how much albumin is excreted in a 24-hour period without requiring patients to collect urine for a whole day.

Common proteinuria blood tests check serum creatinine, albumin, cholesterol and blood glucose levels to help determine whether the condition is caused by kidney damage.

If kidney disease is suspected, any of three tests may be conducted:

  • Glomerular filtration rate (GFR): Estimates how much blood passes through these tiny filters. Normal results range from 90 to 120 mL/min,while levels below 60 mL/min for three or more months are a sign of chronic kidney disease.
  • Renal ultrasound scan: Produces an image of the kidneys. It can show obstructions, stones and tumors or cysts.
  • Kidney biopsy: Involves removal of a tiny piece of kidney tissue for examination under a microscope.

Healthy adults usually excrete between 80 and 150 mg of protein in their urine each day, including serum globulins and albumin. This is quite low because larger proteins are not able to pass through the glomerular membrane into the kidney and the majority of those that do are reabsorbed into the blood stream in the proximal tubule.

However, in some cases there may be an abnormality in the function of the glomerulus, proximal tubule or production of proteins, leading to the presence of excess protein in the urine.

Clinical proteinuria is classified as 0.5 g of protein or more excreted in a 24-hour period or with an albumin:creatinine ratio of 30 mg/mmol or more.


Protein:Creatinine Ratio

Proteinuria can also be diagnosed with a single urine sample by calculating the protein:creatinine ratio.

When the kidneys are functioning normally, they remove creatinine from the blood to keep the levels in the blood and urine in balance. The ratio of the protein to creatinine in the urine sample is a good indicator of the quantity of protein that is excreted in a 24-hour period and can, therefore, be used in the diagnostic process. An individual that excretes more than 30 mg of albumin for every g of creatinine is considered to have proteinuria

Treating proteinuria

Because proteinuria is a symptom and not a disease itself, medical care focuses on treating the underlying condition, such as normalizing blood pressure in people with hypertension or controlling blood sugar levels in those with diabetes.

People with nephrotic syndrome and fluid overload should restrict salt in their diet. The nephrologist may also recommend a mild restriction in protein intake.

ACE inhibitors are medications used primarily for the treatment of hypertension, but they’re also very effective in reducing proteinuria regardless of whether the patient has hypertension or not.

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