Now I see the Tibetan Urinalysis post below, and in there is a section on frothy urine, so hey here it is:
Urinalysis while the urine is still hot: color, vapor, smell and froth:
If the froth or bubbles on the urine have a bluish tint and are large, this indicates a wind disorder.
If the bubbles are small and many and, when stirred, pop quickly, it indicates a bile disorder.
If the bubbles remain static on the surface of the urine like the bubbles of saliva, as if you spit into water, this indicates a phlegm disorder.
If the bubbles have a reddish tint, this indicates a blood disorder.
If they are varicolored like a rainbow, this indicates poisoning.
If they form in the cup and then very quickly disband like a flock of pigeons or doves who are dive-bombed by a hawk and go off in all directions, this indicates an old disorder which now pervades the body; it has become serious.
Four points have been described, and so it is, be well.