The internal causes of the disease originate from asthenia of the lung, spleen and kidney due to the congenitally weak spleen and kidney, or weak physique due to the improper nursing after the chronic disease. The spleen dominates transportation and transformation. If the spleen is asthenic, it will fail to transport body fluid for the stomach and cause excessive internal accumulation of water and dampness in the skin and muscles, finally developing into edema. When the spleen is too weak to control the kidney, the splenic disease may involve the kidney.

The kidney, as the lower source of water, regulates water metabolism and controls urinary excretion. Deficiency of the kidney yang fails to regulate water metabolism while abnormal excretion causes retention of water. Besides, yang deficiency of the kidney fails to warm the spleen, causes asthenia of both the spleen and kidney, giving rise to repeated onset of edema. Symptoms of yin deficiency of the liver and kidney appear in some of the cases of yang impairment involving yin and the kidney failing to nourish the liver. Prolonged disease invading collaterals causes internal blood stasis, manifested by simultaneous existence of blood stasis due to qi stagnation and edema.