Spleen and kidneys have a very close relationship. We can understand it like this: kidneys are nourished by the nutrients from digestion. They need to gather enough energy to supply other organs in order that they can do their own work in turn. When the spleen is weak for a long time, the kidneys will be compromised. When the kidneys are weak, they don’t have enough energy to supply to the spleen! This is a vicious cycle.