Why kidney disease patients have symptoms like high creatinine?

Take an example, like a sewer, wastes and toxins produced in our body are discharged out by kidney, creatinine as a metabolic product of micro-molecule, it can be discharged smoothly by urine. So we take it as an important index measuring kidney detoxification ability. Kidney compensatory ability is strong, it is meaning that only 25% kidney unit and kidney cells can guarantee the detoxification need, the level of creatinine also can keep in the normal range, once creatinine level goes up, which shows that there are over 75% kidney units and kidney cells has been damaged seriously, it can not detoxificate normally, or the sewer is blocked by sewer, and it will be more and more serious until it can’t flow.