When does foamy urine matter?

Some patients are frightened when their urine becomes foamy and think something is wrong with their kidneys. Others noticed it a month ago and did not think it mattered. Both reactions are understandable. The truth is that foamy urine can mean nothing, but sometimes it is a sign of protein in the urine, and the way to find out is a simple test.

Where does the foam come from?

NKF and NIDDK say that a lot of protein in the urine can create bubbles or foam. NKF considers repeated foam a possible “sign of protein in the urine” and says to ask your doctor about an ACR test in that case. But foam can have other causes too, and you cannot tell from looking at the urine whether protein is present. So foam is a sign to be confirmed or ruled out by a test, not a diagnosis.

What the kidney does with protein

A healthy kidney keeps albumin in the blood. NKF writes that when the kidney’s filters (the glomeruli) are damaged, albumin goes into the urine. Albuminuria is not itself a disease. It is a sign of kidney damage and can be seen even when eGFR is still above 60.

Temporary causes of protein in the urine according to NKF: dehydration, hard exercise, fever or infection, and a flare of heart failure. Chronic causes: diabetes, high blood pressure, heart disease and diseases of the kidney’s filters such as IgA nephropathy, lupus and FSGS. For this reason the doctor repeats the test.

When should you have a test?

There is no need to panic, but do not put off a test in these situations:

• The foam is repeated or increases over weeks.
• You have new swelling: puffiness around the eyes in the morning, or swollen feet and ankles (NKF and NIDDK). NKF says swelling can come from the heart or liver too, but it needs to be checked.
• You have high blood pressure, diabetes, heart disease or a family history of kidney disease.
• Your urine has turned pink, red or brown. NKF says to tell your doctor about blood in the urine right away.
• Sudden weight gain, or blood pressure that has newly gone up.

Which test?

NIDDK names the urine test for protein and red blood cells, and NKF considers the urine albumin-to-creatinine ratio (ACR) the main test. NKF gives the categories (mg/g):

• Less than 30: normal.
• 30 to 299: moderately increased.
• 300 or more: severely increased.

A value of 30 or more usually needs to be repeated within three to six months to see whether it persists (NKF). A blood test for creatinine and eGFR is taken alongside. NIDDK says that if albumin is found, the test is repeated one or two more times. In some cases an ultrasound or a biopsy is also needed to find the cause.

Give the urine sample as the lab tells you. If you do not remember something, ask.

If protein is found in the urine

NKF writes that the aim of treatment is to reduce the risk of complications, from kidney failure to heart disease, and it begins with controlling blood pressure and blood sugar. Some blood pressure medicines (with the endings “-pril” or “-sartan”) are usually the first choice, and some other medicines may also be used. The choice depends on your situation and is for your doctor. NKF says these two groups should not be taken together, so do not add a medicine without your doctor’s advice. If both are on your prescription, do not stop them; ask your doctor.

If the cause is a disease of the filters, NIDDK says assessment must continue and treatment is set according to the cause. In nephrotic syndrome NKF says to cut down on salt and not to follow a high-protein diet.

What not to do

• Do not diagnose yourself from the colour or amount of foam.
• Do not start a “kidney cleanse” tea or supplement.
• Do not stop your blood pressure medicine on your own.
• Do not put swelling down to “tiredness” or “too much salt” if it is new.

When is it urgent?

Foamy urine together with very little urine, sudden swelling, shortness of breath, flank pain with fever and chills, or a lot of blood in the urine is urgent. In Iran, call 115, Iran’s emergency number. See the full list in the guide “When to get urgent help”.