Which organ filters out urea, water, and salt as blood flows through it?

The answer is kidney. Excretory system is the system in the body that collects wastes produced by cells and removes the wastes from the body. Kidney is the major organ of the excretory system that filters, blood, eliminates urea, excess water, salt and other waste materials from the body through the blood. It also regulates the fluids levels in the body.