The kidneys filter the body of waste and toxins in the body and return amino acids, glucose, hormones, vitamins, and other essential substances into the bloodstream. Kidneys have small blood vessels called glomeruli that remove the waste where it leaves through the urine. Besides filtering waste materials and drugs from the body, the kidneys balance the body’s fluids, regulate blood pressure, control red blood cells production, and produce an active form of vitamin D.

Protein in the Urine

The production of urine involves a process of filtration, reabsorption, and secretion to maintain a stable balance of body chemicals. Each kidney has over 1 million tiny structures called nephrons which have a glomerulus, where blood filtration happens. As the blood flows through the glomerulus, blood pressure pushes water. It dissolves from the capillaries into the capsule through a filtration membrane, thus beginning the urine formation process.

Urine is composed of 95% water and 5% waste materials. The waste excreted in urine includes ammonia, creatinine, urea, and uric acid. Protein can leak into your urine when you have CKD. A high level of protein in the urine is called proteinuria. Proteinuria has different types which include:

  • Glomerular proteinuria 
  • Tubular proteinuria
  • Overflow proteinuria 
  • Post renal proteinuria

What causes high protein in the urine?

proteinuria meaning

Normally, glomeruli in the kidneys filter the waste products and excess water from the blood. However, if your kidneys aren’t working properly, proteins such as albumin may leak from the blood into the urine. If the glomeruli or tubules are damaged or if there is an excessive protein in the body, proteins will flow into the urine. Proteinuria can also happen when your body produces too much protein, such as albumin. 

Chronic Kidney Disease often doesn’t manifest early symptoms, but protein in the urine might be one of its early signs. Your medical provider may spot proteinuria on a urine test during a routine test.

Proteinuria can be an early indication of chronic kidney disease. Besides CKD, other kidney-harming medical conditions, that can trigger proteinuria, are:

1.) Autoimmune Diseases

The immune system makes antibodies and immunoglobulins that attack the body’s tissues if you have an autoimmune disease. When these antibodies (autoantibodies), attack the tissues, it can injure the glomeruli and cause inflammation. This condition can damage the kidneys, eventually causing, proteinuria. The most common autoimmune diseases that can cause proteinuria are Lupus and Goodpasture syndrome.

Lupus is a long-term autoimmune disease that can cause organ damage, joint pain, fever, and skin rashes. Meanwhile, Goodpasture syndrome is a group of acute illnesses that attacks the healthy lungs and kidneys. It  can quickly progress to an inflammation of the kidneys (glomerulonephritis) and kidney failure.

2.) Cancer

The presence of proteinuria was related to increased cancer mortality in early-stage of colorectal cancer. Consequently, proteinuria can also be due to certain types of cancer such as renal cell carcinoma, lung cancer, breast cancer, colorectal cancer, and multiple myeloma. It is said that the inflammatory effect of cancer affects kidney function. As the kidney function declines, more protein leaks in the urine.

3.) Dehydration

Dehydration is a common temporary cause of proteinuria. The body uses water to send out nutrients to the kidneys, but without enough hydration, the body may have difficulty to efficiently perform its role. As a result, the kidneys cannot recapture protein properly, causing protein to end up in the urine.

Dehydration symptoms can range from mild, moderate to severe depending on the body weight lost through fluids. The first early signs of dehydration include thirst and dark-colored urine, indicating that the body tries to increase water intake and minimize water loss. Additionally, you may also feel exhausted, dizzy, headaches, dry mouth or skin when you are dehydrated.

4.) High blood pressure

High blood pressure weakens the blood vessels in the kidneys, decreasing the blood vessels’ ability to reabsorb protein. Most cases of high blood pressure or hypertension don’t have underlying causes. Nevertheless, people with kidney disease, thyroid problems, adrenal gland tumors and taking birth control pills can trigger hypertension.

5.) Glomerulonephritis

Glomerulonephritis is the inflammation of the glomeruli. When the glomeruli filter blood, they reabsorb protein. Protein can pass through and enter the urine when the glomeruli are damaged. Glomerulonephritis may also cause high blood pressure and red blood cells in the urine called hematuria. This condition happens when the immune system attacks the kidneys.

6.) Diabetes mellitus

When you have diabetes, high blood sugar forces the kidneys to over filter the blood, potentially causing kidney damage. Damaged kidneys cause the protein to leak into the urine.

7.) Chronic Kidney Disease

Chronic Kidney Disease may cause proteinuria in the early stages, although it doesn’t usually manifest noticeable symptoms. CKD is a long-term condition where the kidneys don’t perform as well as they should. When you have underlying conditions, such as diabetes, heart disease, high blood pressure, and glomerulonephritis, there is a greater risk that kidney damage could lead to CKD.

What are the symptoms of proteinuria?

Most people who have proteinuria won’t notice any symptoms, especially in early or mild cases. A lab test will confirm it. As the proteinuria gets worse, you might notice:

  • Urine to appear foamy, frothy, or bubbly
  • Swelling in the face, hands, abdomen, and or feet
  • More frequent urination
  • Shortness of breath
  • Fatigue
  • Nausea or vomiting
  • Lack of appetite
  • Muscle cramping at night
  • Puffiness around the eyes

These symptoms are also similar to chronic kidney disease. If you are noticing these symptoms, consult a doctor immediately.

How is proteinuria diagnosed?

urinalysis

A urine test (urinalysis) can tell whether you have proteinuria or not. The patient provides a urine sample, where a lab technician will dip the pee in a stick with chemicals on the end.  The chemical tip of the dipstick changes color if there is too much substance in the urine. The remaining part of the urine is tested under a microscope, doctors look for substances that don’t belong in the urine. These substances can be bacteria, crystals, and red and white blood cells that can grow and become kidney stones.

If your doctor suspects kidney disease, they would repeat the urine test thrice over three months. If your samples return positive for proteins each time, this could indicate that you have kidney disease. The earlier the diagnosis, the more chances you can have to slow down the disease and stop it from progressing.

Besides urinalysis, you might have additional tests such as:

- Blood tests

It measures the levels of creatinine (chemical waste products) in the body. Creatinine remains in the blood if the kidneys are not working properly. The blood test also measures the Glomerular Filtration Rate (GFR). The GFR compares your age, sex, race to levels of creatinine and albumin in your blood. Your GFR will show your doctor whether or not your kidneys are performing well and how far your CKD has advanced, if already diagnosed previously. A blood test will also measure all proteins in the serum, which is the protein part of the blood.

Blood tests

- Imaging tests (CT scans and Ultrasound)

These tests show kidney images to help doctors spot issues like kidney stones, tumors, or obstruction of the urinary tract.

- Urine Protein Electrophoresis

Doctors search for specific types of proteins in a urine sample. For example, the presence of a protein called Bence-Jones might indicate multiple myeloma (cancer of plasma cells).

Urine Protein Electrophoresis

- Kidney Biopsy

This test involves the removal of a tiny piece of the kidney. The sample is examined under a microscope to identify the cause of kidney disease and the extent of the damage.

How is proteinuria treated?

The treatment for proteinuria depends on its underlying cause.  You won’t possibly need treatment if you have temporary or mild proteinuria. However, if you have consistent proteinuria, you will need to address its cause.

If you have CKD, your treatment plan may include dietary changes, weight management, exercise and medication. If you have hypertension or diabetes, you may need medication to control both your blood sugar and blood pressure. Meanwhile, if the proteinuria isn’t associated with diabetes or other medical condition, you might still be prescribed blood pressure medication to avoid kidney damage. 

dietary changes

When you have CKD, protein in the urine may be a sign that you need to adjust your treatment plans. Drinking water will not treat the cause of protein leaks in the urine unless you are dehydrated. Drinking water will only dilute your urine, but it will not stop the cause of the leaking protein. You might need to also adjust protein consumption.


The Bottom Line

Proteinuria typically means that your kidneys aren’t functioning properly. Leaking protein in your urine cannot be prevented, but treating the underlying causes can assuage it. Consult your doctor if you are manifesting some symptoms of proteinuria, so he/she can come up with a treatment plan to protect your kidneys from further damage. Lifestyle change should be part of your treatment plan, ask your doctor for recommendations to slow down the progression of your CKD.

Sources:

https://www.kidneyfund.org/kidney-disease/kidney-problems/protein-in-urine.html

https://www.freseniuskidneycare.com/thrive-central/protein-in-urine

Proteinuria Causes, Symptoms, and Treatment -
https://www.healthline.com/health/what-causes-protein-in-urine#summary

Filtration, Reabsorption, Secretion: The Three Steps of Urine Formation -
https://www.visiblebody.com/learn/urinary/urine-creation


Albuminuria -
https://www.kidney.org/atoz/content/albuminuria


Proteinuria in Adults: A Diagnostic Approach -
https://www.aafp.org/afp/2000/0915/p1333.html