Proteinuria is the presence of too much protein in the urine. It is typically a sign of kidney disease but can occur with other medical conditions.

One of the main signs of proteinuria is foamy urine. However, healthy people can experience foamy urine, and it can develop with conditions besides kidney disease.

In many people, proteinuria will have no symptoms. If researched further, most cases will not be linked to an underlying cause. Therefore, it may be an incidental finding or a more definitive cause may be identified if other symptoms are present.

This article looks at the symptoms of underlying conditions associated with protein in the urine, causes of protein in the urine, and how proteinuria is diagnosed and treated. It also explains when to see a healthcare provider if you suspect you have proteinuria or any conditions that cause it.

Symptoms of Proteinuria

Under normal circumstances, there is very little protein in your urine. The kidneys have a very good filtration barrier that prevents most proteins from leaving the blood, and those that do make it through are simply reabsorbed back into circulation.

Different mechanisms can permit protein to escape into the urine, including even transient proteinuria due to posture changes called postural proteinuria.

Foamy urine is not diagnostic of proteinuria. In fact, some people may have bilirubinuria (excess bilirubin in the urine) or retrograde ejaculation (the backflow of semen into the bladder).

If the kidneys have sustained only mild damage, proteinuria may be minimal to moderate, depending upon where in the kidney the damage has occurred. On the other hand, if the loss of kidney function is severe, proteinuria may be a contributor to nephrotic syndrome in which fluids and dyslipidemia (unhealthy levels of cholesterol or fats) present a more serious condition.

Symptoms of nephrotic syndrome include:

• Foamy urine
• Swelling of the hands and feet
• Puffiness around the eyes, particularly in the morning
• The buildup of fluids in the abdomen
• Shortness of breath
• Fatigue or tiredness

Causes of Proteinuria

Kidney disease is usually the first condition a healthcare provider will explore when there is excess protein in the urine. But other conditions can cause proteinuria, some of which occur independently of kidney disease.

Kidney Disease

Proteinuria is a common feature of kidney disease. It is typically caused by damage to the tiny clusters of blood vessels that act as filters in the kidneys, called glomeruli. When these filters are damaged, more protein can escape into the urine.

The causes of this are many and are collectively referred to as glomerular disease.

Proteinuria can also be caused by damage to tiny structures called proximal tubules that return protein to the bloodstream. When these units are damaged, there is nowhere for the excess protein to go but out of the body in urine.

Proteinuria is common with the two main types of kidney disease:

• Acute kidney injury (AKI): This is the sudden decline in kidney infection due to dehydration, low blood pressure, shock, congestive heart failure (the heart cannot pump enough blood for the body's needs), blood or fluid loss, and other causes.
• Chronic kidney disease (CKD): This is progressive loss of kidney function, mainly due to high blood pressure, diabetes, glomerular disease, and polycystic kidney disease (a genetic disease that causes clusters of cysts in the kidneys).

Other conditions that affect the kidney can lead to proteinuria and include:

• Fanconi's syndrome: A genetic disorder that can damage proximal tubules
• Goodpasture syndrome: An autoimmune disease affecting the lungs and kidneys
• Granulomatosis with polyangiitis: An autoimmune disease that causes the inflammation of blood vessels throughout the body
• Lupus: An autoimmune disease that affects multiple organs
  
• Preeclampsia: A pregnancy complication characterized by high blood pressure
• Renal cell carcinoma: The most common type of kidney cancer
  

Overflow Proteinuria

Overflow proteinuria is when the amount of low molecular weight proteins in the blood exceeds the amount the kidneys can filter. When this happens, the excess protein exits the body in urine.

Certain conditions can cause overproduction of proteins that, in turn, leads to overflow proteinuria:

• Multiple myeloma: A rare type of blood cancer that can lead to an excessive accumulation of proteins called light chains
• Rhabdomyolysis: The abnormal breakdown of muscle tissues that can lead to the buildup of proteins called myoglobulins

Medications

There are certain medications that can cause proteinuria. These drugs are classified as nephrotoxic because they are toxic to the kidneys.

Some nephrotoxic drugs can damage the tubules and glomeruli of the kidneys as well as the tissues in between. Others cause the formation of crystals that block tubules, while others still cause the breakdown of muscle fibers (rhabdomyolysis) that triggers the overproduction of protein.

The class of drugs commonly associated with nephrotoxicity are:

• Antibiotics: Used to treat bacterial infections
• Angiotensin-receptor blockers (ARBs): Used to treat high blood pressure
• Chemotherapy drugs: Used to treat cancer
• Illicit drugs: Including heroin, methadone, methamphetamine
• Nonsteroidal anti-inflammatory drugs (NSAIDs): Used to reduce inflammation and pain
• Rifampin: Used to treat tuberculosis

How to Treat Proteinuria

Proteinuria is not a disease but rather a condition caused by another illness. As such, the treatment is mainly focused on resolving or managing the underlying cause.

For instance, the symptoms of acute kidney injury—formerly known as acute kidney failure—will usually clear once the underlying condition is treated. In most cases, the kidney function will return to normal with no permanent damage to the kidneys.

With chronic kidney disease (CKD), the focus is placed on improving the function of the kidneys to slow the progression of the disease. With respect to proteinuria, lifestyle measures (such as diet, exercise, and weight loss) will help control diabetes and high blood pressure as ways to slow progression of the disease.

In addition, medications like ACE inhibitors and angiotensin II receptor blockers help reduce urine protein levels. Statin drugs, used to reduce cholesterol, appear to have similar benefits in people with CKD.

Are There Tests to Diagnose the Cause of Proteinuria?

Proteinuria itself can be diagnosed with a simple dipstick test. This involves dipping a specially treated paper strip into a sample of urine. Results are returned within one to two minutes.

To measure the exact amount of protein excreted in the urine, your healthcare provider may recommend a 24-hour urine collection test. By evaluating the composition of urine collected over 24 hours (including different types of proteins and waste products), the lab can calculate how much protein is passed each day.

While these tests can tell you whether or not you have proteinuria, they cannot tell you what caused it if you do. For this, you would need to see a healthcare provider.

To determine the cause of proteinuria, the healthcare provider may order one or several of the following tests:

• Blood tests: The comprehensive metabolic panel includes kidney function tests and glucose. This checks how well your kidneys are filtering blood a waste product called creatinine. Also, glucose is determined and followed up for uncontrolled diabetes, if appropriate. A hemoglobin A1c test also checks for glucose control.
• Urinalysis: This is a urine test that can measure levels of a type of protein called albumin, characteristically seen in people with proteinuria. It can also check for signs of infection (based on the presence of white blood cells) or evidence of bleeding.
• Blood pressure: Checks to see if you have low blood pressure.
• Toxicology test: Can check blood or urine for the presence of nephrotoxic substances, including illicit drugs.
• Special imaging tests: These could include ultrasound (uses sound waves), computed tomography (CT) (creates three-dimensional X-ray images), or magnetic resonance imaging (MRI) (uses magnetic and radio waves).
• Kidney biopsy: This involves the insertion of a long, hollow needle through the wall of the abdomen to obtain a sample of kidney tissue. The anatomic pathologist can then evaluate the sample to check for signs of infection, necrosis (tissue death), cancer, or other abnormalities.

When to See a Healthcare Provider

It can be difficult to know when it's time to see a healthcare provider about proteinuria because the symptoms are often so vague (and occasionally non-existent). Even if you have foamy urine, you might figure that it was "something you ate" if you are otherwise feeling healthy.

And, that can be a problem. Because not only is proteinuria an indication that you may have kidney disease, it is often a sign that kidney disease is advancing and becoming more serious.

To this end, you need to seek immediate medical care if you experience the following:

• Gradually diminishing urine output
• Swelling of the legs, ankles, or feet
• Extreme tiredness or weakness
• Shortness of breath
• Nausea or vomiting
• Chest pain or pressure
• Irregular heartbeat

These are common signs of kidney failure, a condition in which the kidney function has dropped so severely that you may require hospitalization to avoid illness or death.

This is especially true if the symptoms develop over the span of several hours or days. Without treatment, kidney failure is associated with a high risk of death.

Summary

Proteinuria is the presence of excess presence of protein in the urine. It commonly occurs in people with kidney disease when the filters of the kidneys, called the glomeruli, are damaged. But, there are other causes as well, including drugs that are toxic to the kidneys and medical conditions that cause the excess production of protein in the body.

Proteinuria can be diagnosed with a simple urine dipstick test. The underlying cause may require blood and urine tests, imaging tests like ultrasound, and a kidney biopsy to pinpoint the cause.

The treatment of proteinuria varies by the underlying cause. If chronic kidney disease (CKD) is involved, exercise, changes in diet, weight loss, and medications may help slow the progression of the disease and help alleviate proteinuria.

A Word From Verywell

The problem with kidney disease is you often don't know you have it until the damage is done. According to the Center for Disease Control and Prevention (CDC), two of every five adults living with severe kidney disease don't realize they have it.

If you suspect you have a kidney problem—or have a family history of kidney disease—don't ignore the signs and symptoms. Get checked out today.