The renal sac (kidney calyces) are two paired formations located in the lateral wall of the abdominal cavity. Each is an arched protrusion of the peritoneum in which the ureters are located. The capacity of the small bag is approximately 4ml. It plays an important role in the mechanism of reabsorption of glucose, amino acids, vitamins and other useful substances. However, this bag is damaged not only in patients with diabetes, but also in healthy people whose exchange of electrolytes and fluids in the body is disrupted.