What are the reason of bubbly & foamy urine? thanks.

Kidney problems: When your kidneys are first starting to have problems, and you do not have a lot of protein in your urine, you will not notice any symptoms. The only way to know if you have protein in your urine is to have a urine test. The test for protein in the urine measures the amount of albumin in your urine, compared to the amount of creatinine in your urine. This is called the urine albumin-to-creatinine ratio (UACR). A UACR more than 30 mg/g can be a sign of kidney disease. When your kidney damage gets worse and large amounts of protein escape through your urine, you may notice the following symptoms: •Foamy, frothy or bubbly-looking urine when you use the toilet •Swelling in your hands, feet, abdomen or face If you are having these symptoms, your kidney damage may already be severe. Talk to your health care provider immediately about what may be causing your symptoms and what treatment is best for you.