吐泻，胃与肠之病也。病于胃则吐，病于肠则泻，病于肠胃则吐泻交作。然胃与肠虽以幽门为界而究属衔
接连通者，故胃病有时亦能致泻，肠病有时亦能致吐，吐与泻之为病，肠与胃恒互有牵涉也。且也为胃行其精
液者在脾，为肠分别水谷者亦在脾，则胃与肠之运化，皆统属于脾。故吐泻之为病，其关键又莫不在
脾也。其病在小儿患之，倍重于成人，以小儿消化力薄，肠胃俱弱，难任吐泻之戕贼。若后天之谷气一伤，
则生生之机告绝，故自来治儿科者，莫不以吐泻为重证也。夫吐泻虽有虚有实，有寒有热，然吐则气逆，泻
则气陷，久吐则胃虚，久泻则脾伤，不论虚实寒热，其结果皆足使正气受劫，变端百出，一身全局，俱受
其累，重者上吐下泻，顿时上下俱脱，正气乏绝，轻者转成惊风，或渐变疳症。此小儿吐泻一起，所以不可
不急治之以防变也。惟小儿吐泻，缓治虽多变，急治常易愈，当其初作之时，先宜辨其因热因寒因食因痰之
分，再察其虚实之偏，则治法莫不中肯。若拘于暴吐属实，久吐必虚，暴泻宜利，久泻宜止之成见，
则暴作吐泻，往往有属于虚寒者，而久吐久泻亦间有挟积挟痰者，正未可以一概论，是在临证之能持其大者要
者，斡旋以为治耳。兹就吐与泻及吐泻交作三证分论之。
吐泻，是胃和肠的疾病。病在胃则呕吐，病在肠则泄泻，病在肠胃则呕吐与泄泻交替发作。然而胃与肠虽然以幽门为界限，但终究是相连通的结构，所以胃病有时也能导致泄泻，肠病有时也能导致呕吐，呕吐与泄泻这两种病症，肠道与胃常常互相牵涉影响。而且脾负责为胃输送精微物质，脾也负责为肠分别水谷清浊，那么胃与肠的运化功能，都统属于脾管辖。所以吐泻这类疾病，其关键又无不在脾脏。这种病发生在小儿身上，比成人更为严重，因为小儿消化能力薄弱，肠胃都很虚弱，难以承受吐泻对身体的侵害。如果后天摄入的水谷之气一旦受损，那么生命生长的生机就会断绝，所以自古以来治疗儿科疾病的医生，没有不把吐泻视为危重证候的。吐泻虽然有虚证和实证的区别，有寒证和热证的差异，但呕吐会导致气机上逆，泄泻会导致气机下陷，长期呕吐则胃气虚弱，长期泄泻则脾脏受伤，不论虚实寒热的具体情况，最终结果都足以使人体正气受到劫夺，各种病变层出不穷，全身整体都会受到牵连，严重的会上下同时剧烈吐泻，顿时出现上下气脱的危象，正气匮乏断绝；轻微的则会转变成惊风（小儿抽搐痉挛），或者逐渐演变为疳症（小儿慢性营养障碍性疾病）。这就是小儿一旦发生吐泻，所以不能不立即治疗以防病情变化的原因。只是小儿吐泻，缓慢治疗虽然容易变生他证，紧急治疗却往往容易痊愈，在其刚发作的时候，先应当辨别是因热、因寒、因食积、因痰饮引起的区别，再观察其虚实的偏向，那么治疗方法就没有不切中要害的。如果拘泥于“暴吐属实，久吐必虚，暴泻宜利，久泻宜止”的成见，那么突然发作的吐泻，往往也有属于虚寒类型的，而长期吐泻中间也有夹杂积滞或痰饮的情况，正不可以一概而论，这在于临证时能够把握主要矛盾，灵活施治罢了。现在就将呕吐、泄泻以及吐泻交作这三种证候分别论述。
Vomiting and diarrhea are diseases of the stomach and intestines. When the disease is in the stomach, vomiting occurs; when it is in the intestines, diarrhea occurs; when both stomach and intestines are affected, vomiting and diarrhea occur alternately. Although the stomach and intestines are demarcated by the pylorus (Yōumén), they are fundamentally connected and continuous structures. Therefore, stomach diseases can sometimes cause diarrhea, and intestinal diseases can sometimes cause vomiting. In terms of these two pathological conditions, the intestines and stomach often involve each other. Furthermore, the Spleen (Pí) is responsible for transporting essence and fluids for the Stomach, and it also distinguishes clear from turbid within the food and drink for the Intestines. Thus, the transformation and transportation functions of both the stomach and intestines are governed by the Spleen. Consequently, the key to vomiting and diarrhea lies primarily in the Spleen. This condition is more severe in children than in adults because children have weak digestive power and fragile stomachs and intestines, making them unable to withstand the damaging effects of vomiting and diarrhea. If the Qi of acquired nutrition (Hòutiān zhī Gǔqì) is injured, the vital mechanism of growth and life may cease. Therefore, pediatricians throughout history have always regarded vomiting and diarrhea as critical syndromes.
Although vomiting and diarrhea can be classified into deficiency and excess patterns, as well as cold and heat patterns, vomiting leads to rebellious Qi, while diarrhea leads to sinking Qi. Prolonged vomiting weakens the Stomach, and prolonged diarrhea injures the Spleen. Regardless of whether the pattern is deficient or excess, cold or heat, the outcome invariably depletes the body's Righteous Qi (Zhèngqì), leading to various complications that affect the entire body. Severe cases may present with simultaneous upper vomiting and lower diarrhea, resulting in sudden collapse of Qi at both the upper and lower levels, with Righteous Qi becoming exhausted. Mild cases may transform into Infantile Convulsions (Jīngfēng) or gradually develop into Infantile Malnutrition Syndrome (Gānzhèng). This is why immediate treatment is essential upon the onset of vomiting and diarrhea in children to prevent complications.
However, regarding pediatric vomiting and diarrhea, slow treatment may lead to more changes, whereas prompt treatment often results in a cure. At the initial stage, one should first differentiate the etiology—whether due to Heat, Cold, Food Retention, or Phlegm—and then observe the predominance of deficiency or excess. In this way, therapeutic methods will hit the mark. If one adheres rigidly to the preconceived notion that "acute vomiting indicates excess, chronic vomiting implies deficiency, acute diarrhea requires purgation, and chronic diarrhea requires astringency," errors may occur. Acute vomiting and diarrhea may sometimes belong to deficiency-cold patterns, while chronic vomiting and diarrhea may occasionally involve retained food or phlegm. Therefore, these cannot be generalized. It depends on the clinician's ability to grasp the major aspects during practice and apply flexible treatment strategies. Hereinafter, we will discuss the three syndromes of vomiting, diarrhea, and combined vomiting and diarrhea separately.