Water will help facilitate the materials into and out of the kidneys. Without water, the kidneys will not be able to do their job. The water will help the kidneys filter out the toxins and unwanted things in the body, and then flush out the waste.
If the fish are fresh water fish the kidneys would not work. The fish would die.
Lungs and Kidneys
Mainly the pituitary gland as controller, with the kidneys doing most of the work. (Technically the heart is doing the "work", the kidneys just regulate it.)
Horses are big animals, but their kidneys work in the same way as other kidneys work. The kidneys work by filtering out what the body does not need.
The Urogenital system?
Circulation and kidneys, plus the digestive system.
It reduces the blood volume through greater excretion of water by the kidneys.
Your kidneys do all the work, with some control from the pituitary gland.
hoe is water lost from the kidneys
The kidneys are the principle organ for maintaining salt and water balance. One of the functions of the kidneys is to control the water and salt balance in the body. That is why it is referred to as the main organ of homeostasis.
kidneys
ADH conserves water in kidneys ]