Proteinuria means elevated levels of protein in the urine. It is not a disease, but a sign of some kidney conditions.
Several proteins may leak into urine, but albumin is the most likely. High levels of albumin, specifically, is called albuminuria.
If a person has too much protein in their urine, it usually indicates that their kidneys are not filtering blood correctly.
In this article, we explore the causes and symptoms of proteinuria and look into how doctors detect and treat the issue and its cause.
The kidneys are a pair of organs on either side of the spine below the rib cage.
Inside the kidneys are tiny blood vessels called glomeruli. Their job is to cleanse the blood of toxins and metabolites, which they excrete in the urine.
In healthy kidneys, the glomeruli reabsorb protein and keep it in the blood. The kidneys only filter a trace amount of the protein into the urine.
Protein is one of the body’s main building blocks. Getting the right amount of dietary protein, for example, is vital for growth and repair.
If the kidneys are not working as they should, protein can leak into the urine. Health issues that can cause this include:
Dehydration may cause temporary proteinuria. If the body loses and does not replace liquids, it cannot deliver the necessary nutrients to the kidneys. This causes problems with the way the kidneys reabsorb protein. As a result, they may excrete it in the urine.
Dehydration can cause:
High blood pressure
People with high blood pressure may have weak blood vessels in their kidneys. This can keep the kidneys from reabsorbing protein correctly.
Someone may not know that they have high blood pressure until a routine physical exam flags it.
High blood pressure can develop over several years. It may not cause any symptoms until it becomes more severe. In this case, it may cause headaches, nosebleeds, and shortness of breath.
Diabetes is a disease that affects insulin, a hormone, and results in high levels of blood sugar.
In someone with type 1 diabetes, the pancreas does not produce enough insulin. In a person with type 2, the pancreas makes enough insulin but the body cannot use it efficiently.
Having high blood sugar can force the kidneys to work too hard as they filter the blood, leading to kidney damage. This damage may allow protein to leak into the urine.
People may experience various symptoms of diabetes, including:
- frequent urination
- increased thirst and hunger
- blurry vision
- inflammation of the tiny blood vessels in the kidneys, an issue called glomerulonephritis
Glomerulonephritis refers to inflammation of the glomeruli, tiny blood vessels in the kidneys. It can cause protein to enter the urine, and it can also result in nephrotic syndrome.
Nephrotic syndrome is a set of symptoms that can include:
- swelling of the legs and feet
- high blood pressure
- elevated cholesterol
Changes in the immune system cause some forms of glomerulonephritis. It may also run in families, but the cause is often unclear. A person may have one isolated incidence of this, then develop a chronic form years later.
Chronic kidney disease
Chronic kidney disease (CKD) is also known as chronic renal disease. It is a gradual loss of kidney function. This prevents the kidneys from filtering the blood properly, and it can cause protein to seep into the urine.
Often there are no symptoms in the early stages of CKD, but a person may experience:
- difficulty concentrating
- a reduction in appetite
- trouble sleeping
- swollen feet and ankles
- dry, itchy skin with puffiness around the eyes
- an increase in urination, especially at night
CKD progresses gradually and may eventually lead to kidney failure.
The two primary causes of CKD are diabetes and high blood pressure. Other kidney problems, such as glomerulonephritis, recurring kidney infections, and polycystic kidney disease, can also lead to CKD.
These diseases involve the immune system attacking tissues. This happens as a reaction to “autoantibodies,” which are antibodies, a type of protein, and immunoglobulins, a family of chemicals.
Sometimes, these diseases
Autoimmune diseases that may lead to proteinuria include:
- Systemic lupus erythematosus: Also called SLE, this mainly affects the skin and joints, but it can cause kidney damage.
- IgA nephropathy: This causes immunoglobulin A to build up in the glomeruli, leading to proteinuria.
- Goodpasture’s syndrome: This rare disease can cause life threatening bleeding in the lungs and damage the kidneys, leading to kidney failure.
Preeclampsia is a pregnancy complication that usually begins after 20 weeks. The main sign is high blood pressure that may cause acute kidney injury.
Symptoms of preeclampsia include:
- swelling of the hands and face
- a headache and vision problems
- abdominal pain
- weight gain
People with preeclampsia need careful medical supervision, as it can cause preterm birth.
People with diabetes or high blood pressure have a higher risk of developing proteinuria, the peer-reviewed journal Kidney International confirms.
The journal also reports that people who are African American, Native American, Hispanic, or Pacific Islander are more likely than people of European ancestry to develop proteinuria.
Additional risk factors include:
- being over the age of 65
- being overweight or having obesity
- having preeclampsia
- having a family history of kidney disease
A person with early stage kidney damage may have no symptoms. As the condition progresses, the person may have:
- a swollen face
- swollen hands or feet
- foamy urine
- more frequent urination
- high blood pressure
- high cholesterol
- breathing difficulties
Healthcare professionals test for proteinuria by analyzing a urine sample. This often involves using a plastic tool called a dipstick. It has a coating of chemicals that changes color according to the protein levels in the urine sample.
Dipstick tests are not highly accurate, however, so the doctor may send the urine sample to a laboratory for more precise testing.
Another test involves collecting urine over 24 hours to compare levels of the protein albumin with those of the waste product creatinine.
A healthcare professional may also use a glomeruli filtration rate, or GFR, blood test to determine how well the kidneys filter blood.
The best approach depends on the issue causing proteinuria, its severity, and whether it is temporary or chronic.
A nephrologist, a doctor who specializes in kidney health, may recommend:
- Lifestyle changes: These may include losing weight, exercising more, and stopping smoking.
- Medications: If a person has high blood pressure or diabetes, the doctor may prescribe medications that help control these conditions.
- A special diet: The American Kidney Fund says that a kidney-friendly diet low in minerals and protein may help manage kidney problems.
Proteinuria is high levels of protein in the urine. It shows that the kidneys are not filtering blood as they should.
Causes of proteinuria can be temporary, such as dehydration, or chronic, such as an autoimmune disease. People with diabetes or high blood pressure have the highest risk of proteinuria.
Healthcare professionals treat proteinuria by addressing the underlying cause. They may also suggest a special diet to help improve kidney function.