If the filters in our kidneys are damaged, increased amounts of albumin and other larger proteins from our blood can pass through and escape into the urine.
This abnormal amount of protein in the urine is known as proteinuria.
The level and type of proteinuria are a good indicator of the extent of kidney damage. Sometimes the only protein which leaks out is albumin - this form of proteinuria is also known as albuminuria. Proteinuria is also a sign that someone is at risk of developing progressive worsening of kidney function. Even small degrees of albuminuria/proteinuria are also associated with an increased risk of developing heart and blood vessel disease.
What can cause protein leaks from kidneys?
Many diseases can cause inflammation of the kidney filters, a condition which is also known as glomerulonephritis. Other processes that can damage the kidney filters and cause proteinuria include diabetes, high blood pressure (hypertension), and some other forms of kidney diseases.
Tests to determine proteinuria
The National Institute for Health and Care Excellence (NICE) in the UK recommends that regular urine tests for proteinuria should be carried on:
- Anybody at risk of developing chronic kidney disease (CKD).
- Any patient with reduced kidney function.
To test for kidney problems, your doctor may do an initial dipstick test on a sample of your urine. If your doctor suspects you may have CKD or reduced kidney function then a urine sample (preferably the first urine specimen of the day) will be sent to the local laboratory to be tested. This is the only way to identify small quantities of albumin and to measure the amount of protein present.
You may be asked to repeat the sample, particularly if the first one was not from early in the morning. This is because there are other factors which may cause a small increase in the amount of albumin.
What are the signs of proteinuria?
Large amounts of protein in your urine may cause it to look foamy in the toilet. Also, the loss of protein from your body means your blood can no longer soak up enough fluid, and you may notice swelling in your hands, feet, abdomen, or face. These are signs of very large protein loss: a condition called nephrotic syndrome.
Most people who have proteinuria will not notice any related signs or symptoms. Laboratory testing is the only way to find out how much protein you have in your urine.
Who should have their urine routinely tested for proteinuria?
NICE has suggested that the following people should be considered for a urine test for proteinuria:
- People with kidney function known to be less than 65% of normal. This assessment is made using a blood test for your kidney measurement, called your estimated glomerular filtration rate (eGFR).
- People with diabetes.
- People with high blood pressure (hypertension).
- People with a history of kidney disease such as glomerulonephritis.
- People who have conditions which could damage the kidneys by blocking the outflow of urine (eg, enlarged prostate gland, recurrent kidney stones).
- People with heart and blood vessel (cardiovascular) disease (coronary heart disease, chronic heart failure, peripheral arterial disease and cerebral vascular disease - stroke or TIA).
- People with complex diseases which may involve the kidneys - for example, systemic lupus erythematosus (this is a disease where a person's immune system attacks and injures the body's own organs and tissues) or myeloma.
- People with a family history of kidney failure or a family history of inherited kidney disease.
- People found to have blood in their urine.
How often do I need to have a test for proteinuria?
People who are at increased risk of developing kidney disease should have this test annually as a minimum or as part of their routine check-ups by the doctor. The exact frequency should depend on the clinical situation (level of risk) of the patient. It is important that people with CKD and diabetes should have a test for proteinuria as part of their regular reviews at least once a year.
If I have proteinuria, will I need specific treatment?
If proteinuria is confirmed, your doctor will do other tests and examinations to find out the cause. This may include referral to a kidney (renal) specialist (nephrologist) who will help to develop your kidney care plan. Your treatment may include:
- Lifestyle changes such as losing excess weight, exercising and stopping smoking.
- Sometimes changes in your diet.
If you have diabetes, high blood pressure or both, the first goal of treatment will be to control your blood glucose and blood pressure.
Further reading and references
Chronic kidney disease: early identification and management of chronic kidney disease in adults in primary and secondary care; NICE Clinical Guidelines (July 2014, updated Jan 2015)
Hyperphosphataemia in chronic kidney disease; NICE Clinical Guideline (Mar 2013)
Chronic kidney disease: managing anaemia; NICE Clinical Guideline (June 2015).
Sommerer C, Zeier M; Clinical Manifestation and Management of ADPKD in Western Countries. Kidney Dis (Basel). 2016 Oct2(3):120-127. Epub 2016 Oct 6.
Diet in Renal Disease; Edinburgh Renal Unit
Blann A; Routine blood tests 1: why do we test for urea and electrolytes? Nursing Times 110: 5, 19-21, 2014.
Fraser SD, Blakeman T; Chronic kidney disease: identification and management in primary care. Pragmat Obs Res. 2016 Aug 177:21-32. eCollection 2016.
Alaini A, Malhotra D, Rondon-Berrios H, et al; Establishing the presence or absence of chronic kidney disease: Uses and limitations of formulas estimating the glomerular filtration rate. World J Methodol. 2017 Sep 267(3):73-92. doi: 10.5662/wjm.v7.i3.73. eCollection 2017 Sep 26.
Management of chronic kidney disease; NICE CKS, May 2020 (UK access only)
Chronic kidney disease: what are the causes and risk factors?; NICE CKS, May 2020 (UK access only)