Sometimes there is a small amount of foamy urine under normal circumstances, but when certain diseases occur in the body, the composition of the urine may change, resulting in a large amount of foamy urine. Foamy urine is not always proteinuria. In addition to proteinuria, which can manifest as foamy urine, there are other substances that may also manifest as increased foam in the urine, such as: sugar or ketone bodies, urinary bilirubin, gas produced in the urine by gas-producing bacteria, etc.