Why are kidneys called the osmoregulators?

Kidneys are called osmoregulators since they play a very large and important role in human osmoregulation. They regulate the amount of water in urine waste. With the help of naturally producing hormones such as antidiuretic hormone, aldosterone, and angiotensin II, the human body can increase permeability of the collecting ducts in the kidney to reabsorb water and prevent it from being excreted.