Flesh anhydride and urea nitrogen are the child of protein metabolization, by nephritic eduction body outside, the chroma in its blood can regard reason as the index of function of kidney spherule filtration.

• 肌酐及尿素氮为蛋白质代谢的产物，由肾脏排出体外，故其血中浓度可作为肾小球滤过功能的指标。