The role of the renal tubules is mainly to reabsorb water and electrolytes, and it also has a secretory function. The kidney is like a filter, and the glomerulus and tubules play the main role. After the blood passes through the kidney, it will be filtered by the glomerulus, and most of the filtered substances will be reabsorbed by the renal tubules, so as to maintain the balance of water and electrolytes in the body and prevent dehydration and electrolyte disorders. In addition to reabsorption, when the electrolyte disorder in the body is obvious, such as hyperkalemia, the renal tubules also have a secretory function, which is to secrete the excess potassium into the urine and then excrete it out of the body. Therefore, when the renal tubules are damaged or some receptors are impaired, the corresponding symptoms will appear. For example, when a patient has applied a large amount of nephrotoxic drugs or has rhabdomyolysis, it will manifest as kidney injury, and in the polyuric phase, the renal tubular reabsorption dysfunction will manifest as polyuria.