Diarrhea, also known as diarrhea, is referred to by various names in classical medical texts, with classifications that vary. Neijing often classifies diarrhea based on the condition and the nature of the stool, resulting in names such as lienteric diarrhea, cave diarrhea, pasty diarrhea, watery diarrhea, and damp diarrhea. Nan Jing approaches the topic from the perspective of zang-fu organs, introducing terms like stomach diarrhea, large intestine diarrhea, and small intestine diarrhea. Later scholars either classified diarrhea based on external contraction diseases, differentiating it into damp, fire, qi, phlegm, and accumulation types; or based on internal damage, such as spleen deficiency diarrhea, kidney deficiency diarrhea, liver-spleen disharmony diarrhea, and food accumulation diarrhea.

In the books "Treatise on Cold Damage Diseases" and Jingui Yaolue, diarrhea is referred to as "利" or "diarrhea", with undigested food in diarrhea being called "diarrhea with clear grains". Zhang Zhong-jing also referred to dysentery as "diarrhea", or to distinguish it from diarrhea, sometimes called it "diarrhea with pus and blood", "heat diarrhea with tenesmus", etc. Diarrhea and dysentery are different, as stated in Leizheng Zhicai under the diarrhea section: "Diarrhea arises from the inability to separate water and grains, affecting the middle energizer, while dysentery involves damage to blood and fat, affecting the lower energizer. For the middle energizer, it involves separating dampness from the spleen and stomach, and for the lower energizer, it involves regulating damage to the liver and kidneys." If the stool contains pus and blood with tenesmus, it was anciently called dysentery (dysentery), see the entry on tenesmus.

1. Dampness-heat︰Clinically, it often manifests as an acute onset, pouring diarrhea, discharging yellow watery stools or mucus with a foul odor, accompanied by borborygmus and abdominal pain, as well as burning pain in the anus. It may also be accompanied by chills and fever, thirst with little desire to drink, gastric stuffiness in the chest, dark and scanty urine, yellow and greasy tongue coating, and a slippery, rapid pulse. Dampness-heat diarrhea is mostly caused by the mutual obstruction of dampness-heat in the stomach and intestines, leading to dysfunction in ascending and descending as well as transportation, resulting in the mixing of clear and turbid substances and subsequent diarrhea. Its characteristics include: pouring diarrhea, burning sensation in the anus, borborygmus and abdominal pain, diarrhea immediately after abdominal pain, lingering discomfort after defecation, and yellowish-brown, foul-smelling stools. Neijing states, "Sudden gushing diarrhea with urgency is all attributed to heat." Additionally, because dampness is a yin pathogen with a sticky and greasy nature, symptoms such as gastric stuffiness in the chest, fatigue and heavy body, and loss of appetite may occur. Treatment should focus on clearing heat and resolving dampness, using Pueraria, Skullcap and Coptis Decoction with additions like Akebia Stem and Talc.
2. Cold-dampness︰The stool is loose and not very foul-smelling, with abdominal pain that prefers warmth and pressure, epigastric distension and fullness, undigested food, loss of appetite, and heavy, fatigued limbs. It may be accompanied by chills or fever, headache, clear and pale urine, a white and greasy tongue coating, and a soggy or slow pulse. The spleen, as the organ of Taiyin damp-earth, prefers warmth and dislikes cold, favors dryness and abhors dampness. When the spleen is encumbered by cold-dampness, its functions of ascending, descending, digestion, and transportation become disordered, leading to undigested food passing into the large intestine and causing diarrhea. The characteristics of this diarrhea include borborygmus and loose stools that are not very foul-smelling. Due to internal cold invasion, the abdominal pain prefers heat and warmth. Cold-dampness encumbering the spleen results in epigastric distension and fullness. As dampness transforms with cold, there is a bland taste in the mouth, no thirst, and a white, greasy tongue coating. This differs from dampness-heat diarrhea, which presents with thirst but little desire to drink or thirst without wanting to drink, along with a yellow, greasy tongue coating. Treatment should focus on warming the middle and dissipating cold. The modified Middle-Regulating Decoction with aromatic herbs to resolve dampness may be selected, or Patchouli Qi-Righting Powder with modifications can be used.
3. Food Stagnation︰The symptoms include abdominal pain followed immediately by diarrhea, with the pain alleviated after defecation but recurring shortly thereafter. The stool is thick and sticky or mixed with watery feces, emitting a foul odor. There is chest and epigastric distension and stuffiness, accompanied by belching of foul-smelling gas (acid swallow), abdominal distension and fullness, anorexia, a greasy and dirty tongue coating, and a wiry-slippery pulse. This condition is often caused by dietary irregularities, excessive consumption of greasy or cold foods, leading to spleen and stomach injury and impaired transportation and transformation, resulting in retained food stagnating in the middle energizer and causing diarrhea. The key diagnostic points are: distending pain in the epigastrium and abdomen, relief of abdominal pain after diarrhea, followed by recurrent pain and diarrhea, with loose stools that smell like rotten eggs and contain undigested food residues. Food accumulation in the stomach and intestines leads to stagnation and indigestion, often manifesting as epigastric and abdominal distension and fullness, belching of foul-smelling gas (acid swallow), anorexia, and a greasy tongue coating. The treatment focuses on promoting digestion and removing food stagnation, as well as invigorating the spleen and harmonizing the stomach, using Harmony-Preserving Pill with modifications.
4. Liver and Spleen Disharmony︰Before diarrhea, there is slight distending pain in the stomach; the stool contains incompletely digested food, and the pain does not lessen or may even worsen after diarrhea. It is often triggered by mental stimulation or emotional tension, accompanied by distension or scurrying pain in both flanks, along with symptoms such as poor appetite, acid swallow, belching, and flatus. The tongue texture is pale red with scant coating, and the pulse is wiry. The diarrhea is caused by liver qi transversely counterflowing and overacting on the spleen earth, primarily due to qi stagnation, often induced by emotional tension or mental stimulation. Jingyue Quanshu·"Diarrhea" states: "Whenever diarrhea occurs due to anger, it must first be caused by food stagnation damaging the spleen and stomach during anger. Thus, any trigger immediately provokes a reaction—this is a disease of the liver and spleen, resulting from liver wood overacting on earth and injuring spleen qi." The characteristics of diarrhea include borborygmus before diarrhea, pain that does not lessen or worsens after diarrhea, distending pain or scurrying pain in the hypochondriac region, along with symptoms such as poor appetite, sour taste in the mouth, belching, and flatus. The treatment principle is to soothe the liver and fortify the spleen, modified with Pain and Diarrhea Vital Formula.
5. Heat Accumulation with Diarrhea︰Common symptoms include diarrhea with yellow, foul-smelling watery stools or purely green watery stools, periumbilical pain, abdominal tenderness or palpable masses, epigastric fullness, poor appetite, scanty dark urine, yellow and greasy tongue coating, and a deep, slippery pulse. Heat retention with watery discharge is a manifestation of the yangming fu-organ pattern, where pathogenic heat binds with dry stool internally. Clinically, it is often seen in two scenarios: one arising from external-contraction febrile disease, with dry stool binding internally accompanied by diarrhea of purely foul-smelling watery stools; the other resulting from shaoyin disease where pathogenic factors transform into heat, leading to stagnation of fu-organ qi, presenting with abdominal distension and fullness along with diarrhea of clear water. Its characteristics include: often beginning with constipation followed by diarrhea, abdominal distension, fullness, and pain with tenderness, passing foul-smelling watery stools, sometimes with dry fecal pellets, difficulty in defecation, and periumbilical pain. Treatment focuses on purging heat and unblocking the fu organs, using Major Purgative Decoction with modifications. Additionally, in cases of warm disease where toxic fire pours into the large intestine, there may also be diarrhea of clear water, which should be distinguished from this pattern. She Shiyu's Yizhen Yide in the "Pestilence" section states: "When toxic fire pours into the large intestine, there may be discharge of foul matter, diarrhea of clear water, sudden intestinal evacuation, or undigested food... Examining the symptoms, the body must be very hot, breathing must be rough, urine must be scanty, lips must be parched and purple, with intense thirst for cold drinks, unrelenting abdominal pain, and occasional reversal cold of limbs. Treatment should follow the condition by clearing and promoting discharge." This belongs to pestilence toxic fire pouring into the large intestine, and treatment should focus on clearing heat and removing toxins, using Plague-Clear Toxin-Vanquishing Decoction with modifications.
6. Spleen Deficiency︰The stool is sometimes loose and sometimes watery diarrhea. Eating raw, cold, greasy, or hard-to-digest foods worsens the diarrhea, even leading to undigested food in the stool or duck-like feces. There is dull abdominal pain, with a preference for warmth and pressure, poor appetite, bloating after meals, a shallow yellow complexion, physical fatigue, and mental exhaustion. The tongue texture is pale and swollen with a white coating, and the pulse is deep and thin. Clinically, it often manifests as clear, cold diarrhea with undigested food, resembling duck feces. Those with spleen deficiency often experience cold symptoms, hence the abdominal pain, preference for warmth and pressure, and worsening diarrhea upon consuming raw or cold foods. The main treatment focuses on invigorating the spleen and draining dampness, using the formula Ginseng, Poria and White Atractylodes Powder with modifications. For chronic diarrhea with qi deficiency and sinking, or prolapse of the rectum that does not retract, Middle-Tonifying Qi-Replenishing Decoction is used with added astringent and consolidating herbs.
7. Kidney Deficiency︰Before dawn, there is pain around the navel, followed by borborygmus and diarrhea, with the pain alleviated after defecation. The stool is loose and often mixed with undigested food. There is fear of cold in the waist and abdomen, cold limbs, clear and abundant urine, or increased nocturia. The tongue texture is pale and swollen, often with tooth marks, and the pulse is deep, thin, and weak. These are all signs of deficiency-cold diarrhea, either due to spleen yang deficiency or kidney fire decline. The differences lie in: the spleen governs transportation and transformation, lifting clear qi and distributing nutrients. If middle yang is chronically deficient or cold-dampness directly attacks, spleen yang fails in transformation, clear yang qi fails to ascend, turbid yin fails to descend, and body fluids and waste descend together to the large intestine, causing diarrhea. Suwen．Cangqi Fashi Lun: "In spleen diseases... deficiency leads to abdominal distension and fullness, borborygmus, lienteric diarrhea, and indigestion." Therefore, it is due to insufficient kidney yang and decline of life gate fire, which fails to promote transformation. The characteristics of this diarrhea are: before dawn, pain around the navel, borborygmus followed by diarrhea, relief after defecation. The stool is loose, often containing undigested food, accompanied by soreness and weakness in the waist and knees, clear and abundant urine, increased nocturia, and other symptoms of kidney yang deficiency. Jingyue Quanshu．Diarrhea》: "Now, if kidney yang qi is insufficient, life gate fire declines, and pudendal coldness becomes predominant. Thus, in the early morning hours when yang qi has not yet revived and yin qi is at its peak, it causes profuse diarrhea." There are both differences and close connections. Chronic diarrhea due to spleen deficiency often progresses from the spleen to the kidney, leading to spleen-kidney yang deficiency. Treatment should focus on warming the kidney, strengthening the spleen, and stopping diarrhea, with modifications of the Nine Qi Pills. There are also cases where borborygmus and urgent diarrhea occur immediately after eating, with no issues when not eating, and diarrhea after every meal (commonly called "lu indigestion diarrhea," also known as "fistula disease indigestion diarrhea"), persisting for years. This is also due to spleen-kidney dual deficiency, with true fire failing to digest food, hence diarrhea immediately after eating. Treatment should start with warming the kidney and strengthening the spleen, using modifications of Four Miracle Pill combined with Middle-Regulating Pill.

Food accumulation and liver qi invading the spleen both lead to excess pattern diarrhea. Their similarities include abdominal pain and diarrhea, but one is caused by retained food, while the other is due to spleen deficiency with liver overacting.

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1. Yizong Bidu．Diarrhea: "There are nine methods of treatment: The first is called dilution and drainage, which allows dampness to be expelled through urination... The second is called lifting, using herbs like Shengma, Chaihu, Qianghuo, and Gegen to stimulate stomach qi, causing it to rise and thereby stopping the downward flow. Just as a wet ground dries when blown by the wind, wind-drying herbs are often used. Since dampness is a condition of the earth element and wind is of the wood element, wood can overcome earth, and wind can overcome dampness. This is what is meant by treating a fall by raising. The third is called cooling, where intense heat causes sudden diarrhea, and bitter-cold formulas are used to clear the heat... The fourth is called dispersing and unblocking, where phlegm stagnation, qi stagnation, and food accumulation can all cause diarrhea. These should be addressed according to the symptoms to prevent lingering... The fifth is called sweet moderation. Continuous diarrhea leads to a rapid downward trend, and the more it descends, the harder it is to stop. Sweetness can moderate the middle and effectively halt rapid movements... The sixth is called sour astringency. Prolonged diarrhea causes the qi to scatter and not gather, leading to an inability to control. Sour flavors can assist in the gathering and astringent functions... The seventh is called drying the spleen. If the earth element is strong, water evils will not overflow. Therefore, diarrhea is often caused by dampness in the earth, which stems from spleen deficiency. Strengthening the spleen ensures proper digestion and separation of water and grain. If deficiency is not addressed, dampness will worsen... The eighth is called warming the kidneys. The kidneys govern the two lower orifices and are the root of storage. Although they belong to water, true yang resides within them. A small fire generates qi, and fire is the mother of earth. If this fire declines, how can the triple energizer function and digest the five grains? Therefore, those with chronic deficiency must address cold, and those with spleen deficiency must tonify the kidneys. As the classics say, cold should be warmed. The ninth is called consolidation and astringency. Prolonged watery diarrhea causes the pylorus to become slippery. Even with warming and tonifying treatments, success may not be achieved. Astringent formulas must be used to ensure proper transformation and function."
2. 《Zhang Yuqing's Medical Cases》: "Kidney diarrhea, also known as morning diarrhea, occurs at dawn with sudden urgency. However, liver disease can also cause diarrhea in the morning, as the hours of Yin and Mao belong to wood, which can overpower the earth element during its peak time. How can these similar conditions be distinguished? Kidney diarrhea is due to the decline of life-gate fire without depressive qi, causing sudden diarrhea without pain. In contrast, liver disease with wood overacting on earth involves depressive qi, often causing pain without suddenness. This distinction makes it clear."