I saw a special tea in the shops for your kidneys (orthosiphonis), how will this help renal problems and in what cases wont it help?

Not much. The tea that you mention has been around - called java tea (indonesia) or cat' whiskers plant tea it is a mild diuretic (induce urination) and has been promoted for kidney stones, gout and hypertension. At best it may help bladder stone formation. Not to be used by people with kidney failure (has potassium)the best treatment for kidney stones is to drink a lot of fluids and change your life style.