《黄帝内经·灵枢·五色》
在身体上肾与脐正相对，所以肾所主部位的下方，对应脐的状况。鼻尖上方，对应小肠的状况。
当肾者，脐也。面王以上者，小肠也。
The kidney is right across the navel on the body, so the lower part of the kidney's main location corresponds to the condition of the navel. The part above the tip of the nose corresponds to the condition of the small intestine.