The kidney regulates the water excretion in a frog. It filters all the blood and the byproducts out by adjusting the rate of filtration at the glomerulus. The final product in excretion is mostly urea. kidneys are important organs in the urinary system. They are responsible for cleaning the blood from waste products and also dead red and white blood cells. Then it turns it in to urine which is then removed from the body. Additionally, it mains the amount of water in the body.