Xiaozhang Dan (Distension-Relieving Elixir) for Reducing Edema and Abdominal Bloating
In the Qing-dynasty physician Chen Shiduo’s Zhen Zheng Lu (Records of Pattern Differentiation) there is a formula called “Xiaozhang Dan,” composed of: Rhizoma Atractylodis macrocephalae (Baizhu) 3 qian (9 g), Poria (Fuling) 1 liang (30 g), Radix Ophiopogonis (Maidong) 5 qian (15 g), Radix Rehmanniae preparata (Shudihuang) 5 qian (15 g), Dioscoreae Rhizoma (Huai Shanyao) 1 liang (30 g), Euryales Semen (Qianshi) 5 qian (15 g), Perillae Fructus (Suzi) 1 qian (3 g). Decoct in water, strain, and take warm, 1 dose daily, morning and evening.
According to traditional TCM theory, this formula supplements the lung and fortifies the spleen, and supplements the kidney to promote water metabolism; it is indicated for wheezing, abdominal distension, inhibited urination, loose stools, and generalized edema. Chen Shiduo held that when a person’s lung, spleen, and kidney are all deficient, fluids cannot be properly distributed and discharged, producing wheezing, abdominal distension, difficult urination, and loose stools; treatment must therefore tonify all three organs together. In the formula, Baizhu and Fuling fortify the spleen and promote diuresis; Ophiopogon supplements lung yin while Perilla fruit descends lung qi; prepared Rehmannia, Dioscorea, and Euryale seed nourish kidney yin.
Thus combined, the herbs nourish kidney and lung yin. TCM holds that the lung is the “canopy,” the upper source of water, while the kidney governs the discharge of water; when lung and kidney are tonified together, fluids naturally flow. With moderate spleen-fortifying diuresis, urination naturally increases. Chen Shiduo recorded the formula’s effect: “One dose calms the wheezing somewhat; two doses resolve the distension; ten doses make urination free; twenty doses dispel all swelling of the body.”
This is a fairly comprehensive approach to treating edema. From the description that the edema causes wheezing, the formula targets patients with pleural effusion. Pleural effusion may result from pneumonia or tumors (e.g. lung cancer, pleural mesothelioma); such cases are difficult to treat, because once effusion appears the patient is already weak, and aggressive diuresis further damages healthy qi. Treatment must therefore address both root and manifestation, supporting healthy qi while dispelling the pathogen. By the formula’s logic, Chen Shiduo prioritizes supporting healthy qi and only secondarily dispels evil: except for Perilla fruit, every herb here is tonifying.
In practice, when using diuretic edema-reducing herbs on patients with pleural effusion, if diuresis proceeds too fast without supporting healthy qi, the patient often later develops weak legs; this not only fails to treat the edema but may hasten death. Hence some patients deteriorate rapidly after formulas such as Shi Zao Tang, Peng Zheng Wan, or Zhou Che Wan. As pleural effusion drains, the essential trace element potassium is also lost, causing weak legs. Chen Shiduo’s emphasis on supporting healthy qi—using only small amounts of Baizhu and Fuling to fortify the spleen and promote diuresis—likely reflects his clinical experience, and his wisdom is worth learning from.