My son had protein and blood leaking into his urine as a complication of a step throat - post strepticoccal glomeroluniphritus - not sure of the exact spelling! This caused him to retain fluid and it can also give you high blood pressure. Even after recovery from the infection, it can give ongoing kidney problems - luckily he has recovered fully - I think that the rate of full recovery in a child is about 95%, but I think the chance of a full recovery in an adult is much lower.