1. Gastrointestinal symptoms? When diarrhea occurs, the stool frequency increases, the amount increases and the nature changes. Stool more than 3 times /d, even 10 ~ 20 days, which can be loose stool, mushy stool, watery stool, or mucus purulent bloody stool. Judging the nature of feces is more important than the number of diarrhea. If the stool increases and forms stool, it is not diarrhea. Human breast-fed babies defecate 2 ~ 4 times a day, which is mushy and does not cause diarrhea. Nausea and vomiting are common accompanying symptoms. Serious people will vomit coffee, and some people will have symptoms such as abdominal pain, bloating and loss of appetite. 2. Systemic symptoms? In severe cases, the general symptoms are obvious, most of them have fever, and the body temperature is 38 ~ 40℃, and a few of them are as high as 40℃ or above, which can lead to pallor, restlessness, drowsiness, convulsions and even coma. With the aggravation of systemic symptoms, it can cause disorders of nervous system, heart, liver and kidney function. 3. Water, electrolyte and acid-base balance disorder? Mainly dehydration and metabolic acidosis, and sometimes hypokalemia and hypocalcemia. 4. dehydration? Because diarrhea and vomiting will lose a lot of water and electrolytes, which will reduce the water retention capacity in the body; Severe vomiting, fasting, loss of appetite or refusal to eat reduce food and liquid intake; Children with fever, shortness of breath and acidosis have deepened their breathing, which increases the inconspicuous water loss. According to the amount and nature of water and electrolyte loss, it can be divided into three types: isotonic dehydration (serum sodium concentration 130 ~ 150 mmol/L), hypotonic dehydration (serum sodium concentration 1l) The general manifestations are weight loss, dry mouth, pale or gray skin, poor elasticity, sunken anterior fontanel and orbit, dry mucosa, less tears and less urine. In severe cases, it can lead to circulatory disorder. According to the dehydration degree, it is divided into light, medium and heavy. Dehydration evaluation (table 1). 5. metabolic acidosis? Dehydration often leads to different degrees of metabolic acidosis. The reasons are as follows: a large number of alkaline substances are lost with feces; During dehydration, renal blood flow is insufficient, urine volume decreases, and acid metabolites in the body cannot be excreted in time; Poor intestinal digestion and absorption function, insufficient calorie intake, increased fat oxidation and incomplete metabolism lead to the accumulation of ketone bodies, which can not be excreted from the kidney in time; In severe dehydration, tissue perfusion is insufficient, resulting in tissue hypoxia and lactic acid accumulation. The main manifestations are listlessness, lethargy, deep and long breathing, cherry red lips, unconsciousness in severe cases, poor respiratory compensation function of newborns and infants, and no obvious change in respiratory rhythm, mainly manifested as lethargy, pallor, refusal to eat, fatigue and so on. Pay attention to early detection. 6. Hypokalemia? During diarrhea, the concentration of potassium in stool is about 20 ~ 50 mmol/L. Excessive loss due to vomiting and diarrhea and insufficient intake can not compensate potassium, which may lead to hypokalemia. Its symptoms mostly appear when dehydration and acidosis are corrected and urine volume increases. (1) Causes of frequent hypokalemia during dehydration and acidosis correction: ① During acidosis, extracellular fluid H enters the cell to exchange with K, so intracellular K decreases, but serum potassium does not decrease. Renal function is low during dehydration, and potassium excretion from urine is reduced. After rehydration, especially when infusion of potassium-free solution, serum potassium is diluted and excreted with urine, and potassium is transferred from outside to inside after acidosis is corrected, which is prone to hypokalemia. ② Hypokalemia appears gradually when the course of disease is greater than 1 week. ③ Malnutrition appeared early and seriously. Before dehydration is corrected, the blood potassium concentration can be maintained normal due to blood concentration, acidosis, oliguria and other reasons, and hypokalemia rarely occurs at this time. However, with the gradual correction of dehydration and acidosis and the increase of urine volume, the lack of potassium content gradually appears. (2) Hypokalemia: The serum potassium is below 3.5mmol/L, which is characterized by listlessness, decreased muscle tone, abdominal distension, weakened or disappeared intestinal peristalsis and dull heart sounds. Tendon reflex is weakened or disappeared. In severe cases, coma, intestinal paralysis, respiratory muscle paralysis, slow heart rate, arrhythmia and apical systolic murmur can be life-threatening. Electrocardiogram showed ST segment moving down, T wave depressed, flat, biphasic, inverted, U wave appeared, and P-R interval and Q-T interval were prolonged. 7. Hypocalcemia and hypomagnesemia? It doesn't usually appear. In children with persistent diarrhea, rickets or malnutrition, when correcting acidosis, serum bound calcium increases and ionized calcium decreases, which may lead to hypocalcemia. Showing irritability, convulsions or convulsions. Hypomagnesemia generally appears after correction of low sodium, low potassium and low calcium. The original malnutrition and rickets are more likely to occur, and a few children may have hypomagnesemia, which is manifested as tremors of hands and feet, chorea-like voluntary movement, irritability, severe convulsions, and the symptoms are still not improved after calcium supplementation. 8. Clinical features of several common infectious diarrhea (1) rotavirus enteritis: It is frequent in autumn and winter, sporadic or small-scale epidemic, and the virus is transmitted through fecal-oral route and respiratory tract. It is more common in infants aged 6 to 24 months. The incubation period is 1 ~ 3 days, which is often accompanied by fever and upper respiratory tract infection. Acute onset, first vomiting, then diarrhea, watery stool or egg soup, with a small amount of mucus, no foul smell, several times a day to 10 or more. Often accompanied by dehydration and acidosis. The disease is a self-limited disease, with a course of 3-8 days, a few of which are longer, and occasionally a small amount of white blood cells can be seen in stool microscopy. During the course of 1 ~ 3 days, a large number of viruses were excreted from feces for 6 days. Serum antibodies generally rise after 3 weeks, so it is difficult to isolate the virus. Immunoelectron microscopy, ELISA or nucleic acid electrophoresis are helpful for diagnosis. (2) Norwalk virus enteritis: It is more common in older children and adults, and its clinical manifestations are similar to rotavirus enteritis. (3) Escherichia coli enteritis: It often occurs in May-August, with different degrees of severity. Pathogenic Escherichia coli enteritis stool is egg-flower soup-like, fishy, with more mucus, occasional bloodshot or mucus stool, often accompanied by vomiting, and no fever and systemic symptoms. Mainly manifested as water-electrolyte disorder. Course of disease 1 ~ 2 weeks. Toxin-producing Escherichia coli enteritis has an acute onset, with the main symptoms of vomiting and diarrhea, no white blood cells in water samples, and obvious imbalance of water, electrolyte and acid-base balance, with a course of 5 ~ 10 days. Invasive Escherichia coli enteritis, acute onset, high fever, frequent diarrhea, mucus-like stool with purulent blood, often accompanied by nausea, abdominal pain, acute diarrhea and other symptoms, sometimes severe poisoning symptoms, and even shock. It is difficult to distinguish clinical symptoms from bacillary dysentery, and stool culture is needed to distinguish them. Hemorrhagic E.coli enteritis, increased stool frequency, yellow watery stool at first, bloody stool later, with a special smell. Microscopic examination of stool shows a large number of red blood cells, often without white blood cells. With abdominal pain. May be accompanied by hemolytic uremic syndrome and thrombocytopenic purpura. (4) Campylobacter jejuni enteritis: It can occur all year round, especially in summer. It can be sporadic or popular. The incidence rate of infants aged 6 months to 2 years is the highest, and livestock and poultry are the main sources of infection, which are transmitted from animals to people or from person to person through fecal-oral route. The incubation period is 2 ~ 1 1 day. Acute onset with symptoms similar to bacillary dysentery. Fever, vomiting, abdominal pain, diarrhea, mucus or purulent stool with foul smell. The virulent strain infection can cause watery stool, and a large number of white blood cells and red blood cells can be seen under the microscope, which can be complicated with severe enterocolitis, septicemia, pneumonia, meningitis, endocarditis and pericarditis. (5) yersinia enterocolitica: It mostly happens in winter and spring, especially in infants. The incubation period is about 10 day. No obvious prodromal symptoms. Clinical symptoms are related to age. The main symptom of children under 5 years old is diarrhea, and the feces are watery, mucus-like, pus-like or bloody. Microscopic examination of stool shows a large number of white blood cells, often accompanied by abdominal pain, fever, nausea and vomiting. For those over 5 years old and adolescents, the main manifestations are abdominal pain, high white blood cells and accelerated erythrocyte sedimentation rate, which are similar to acute appendicitis. The disease can be complicated with mesenteric lymphadenitis, erythema nodosum, reactive arthritis, sepsis, myocarditis, acute hepatitis, liver abscess, conjunctivitis, meningitis, urethritis or acute nephritis. Course of disease 1 ~ 3 weeks. (6) Salmonella typhimurium enteritis: It occurs all year round, with the highest incidence from April to September. Most of them are infants under 2 years old, which is easy to be popular in pediatric wards. Oral communication. The incubation period is 8 ~ 24h. The main clinical manifestations are fever, nausea, vomiting, abdominal pain, abdominal distension and "jet-like" diarrhea. The stool frequency can reach more than 30 times, showing yellow or dark green loose stool, watery stool, sticky stool or purulent stool. Microscopic examination of stool showed a large number of white blood cells and different numbers of red blood cells. In severe cases, symptoms of dehydration, acidosis and systemic poisoning may occur, and even shock may cause sepsis and cerebrospinal meningitis. The general course of disease is 2 ~ 4 weeks. The carrying rate is high, and some children are discharged more than 2 months after illness. (7) Staphylococcus aureus enteritis: rarely primary, mostly secondary to the application of a large number of broad-spectrum antibiotics or secondary to chronic diseases. Acute onset, severe poisoning symptoms. It is characterized by fever, vomiting and frequent diarrhea. Different degrees of dehydration, electrolyte disorder, severe shock. At the beginning of the disease, the stool is yellow-green, and after 3 ~ 4 days, it turns foul, watery and sticky. Microscopic examination of stool showed a large number of pus cells and gram-positive bacteria. Stool culture, staphylococcal growth, coagulase positive. (8) Pseudomembranous enteritis: It is common after long-term use of antibiotics. Due to long-term use of antibiotics, the intestinal flora is disordered, which makes Clostridium difficile proliferate and produce necrotic toxins. The main symptoms are diarrhea, yellow watery stool or mucus stool, a few with blood, false membrane discharge (intestinal tube), accompanied by fever, abdominal distension and abdominal pain. Abdominal pain often occurs before or at the same time as diarrhea. Often accompanied by obvious hypoproteinemia, water and electrolyte disorders, general weakness and chronic consumption. Mild children usually stop diarrhea in 5 ~ 8 days after stopping taking medicine, and severe children appear dehydration, shock and even death. If diarrhea occurs in children after drug withdrawal, or if antibiotics continue to be used after diarrhea, the course of disease will often be delayed. (9) Candidal enteritis: It mostly occurs in frail and malnourished children who abuse broad-spectrum antibiotics or adrenocortical hormones for a long time. Oral cavity is often accompanied by thrush. The frequency of defecation increases, the color is light yellow or green, and there are many bubbles. Sometimes there are tofu residue samples (colonies) with mucus, and fungal spores and pseudohyphae can be seen in the stool under microscope. It is helpful for the identification of fecal fungal culture. 9. Children with persistent chronic diarrhea? The etiology is complex, which is currently considered to include infection, allergy, congenital digestive enzyme deficiency, immune deficiency, drug factors, congenital malformation and so on. Diarrhea after infection is the most common. The results of intestinal mucosal biopsy in children with chronic diarrhea show that the persistent damage of intestinal mucosal structure and function or the damage of normal repair mechanism is an important cause of persistent diarrhea in children. (1) has a history of acute diarrhea: acute infectious diarrhea is mostly transient. However, if the host can't produce normal immune response, repeatedly contact with infectious pathogens, or seriously destroy intestinal mucus due to infection, acute diarrhea can turn into chronic diarrhea. Most of them are caused by persistent mucosal injury, and a few are caused by persistent infection. The mucosa of duodenum and jejunum becomes thinner, intestinal villi atrophy, intestinal cells overflow and fall off, and microvilli degeneration accelerates epithelial cell renewal, which may be related to microbial adhesion on the surface of intestinal mucosa. Due to the lack of mucosal regeneration time, these new epithelial cells are similar to crypt cells, so their functions are low. The activity of disaccharidase, especially lactase and brush marginal peptidase decreased, and the effective absorption area decreased, causing indigestion and absorption of various nutrients. In addition, intestinal mucosal injury increases the permeability of pathogenic factors and macromolecules, which makes the mucosa sensitized to foreign antigens. (2) Malnourished children: When diarrhea occurs, all bacteria in the upper intestine increase obviously, and anaerobic bacteria and yeast multiply in the duodenum. Due to the degreasing effect of a large number of bacteria on cholic acid, the concentration of free cholic acid is greatly increased. High concentration of free cholic acid can damage small intestinal cells and hinder the formation of fat particles. The cellular immune function of children with severe malnutrition is lost, and the secretion of antibodies, phagocytic function and complement level are decreased, thus increasing the susceptibility to pathogens and food protein antigens. In short, persistent diarrhea is easy to be malnourished, and malnutrition is easy to prolong the diarrhea time, which is mutually causal and forms a vicious circle.