Causes of diarrhea

Under normal circumstances, most people have a bowel movement once a day. Some people defecate 2-3 times a day or once every 2-3 days, and the characteristics of their stool are normal. This is normal. However, if you have bowel movements more than three times a day or the shape of the stool is abnormal, such as watery stools, bloody stools, jam-like stools, etc., we can call it diarrhea, or loose stools.

In daily life, diarrhea is a very common symptom. Many diseases can cause diarrhea, such as gastroenteritis, viral infection, etc. However, the shape of stool is different for different diseases. We can understand what disease we have based on the shape of stool. Next, let us understand the causes of diarrhea.

1. Causes of acute diarrhea Intestinal infection, including food poisoning, is the most common cause of acute diarrhea and can be divided into:

(1) Bacterial infection:

① Bacterial dysentery: The onset is relatively rapid, often with chills, fever, abdominal pain, diarrhea and tenesmus, which may be accompanied by nausea and vomiting. The diarrhea is characterized by mucus, pus and blood in the stool, with varying frequency per day. Under the microscope, it is found that the stool contains a large number of red blood cells and white blood cells, and stool culture can detect Shigella dysenteriae.

②Salmonella infection: often has a history of unclean food, often with symptoms of abdominal distension, abdominal pain and diarrhea. The stool is mainly loose or watery, with little pus and blood, and the number of bowel movements varies from 3 to 5 times a day. Stool culture can detect pathogenic bacteria (Salmonella or Salmonella typhi, etc.).

③Escherichia coli enteritis: often with a history of unclean diet. The onset is relatively acute, and symptoms may include chills, fever, abdominal pain, diarrhea, and may be accompanied by vomiting. Diarrhea is mostly watery stool, but may also contain mucus, pus and blood. Stool culture can detect pathogenic bacteria.

④ Campylobacter infection: The symptoms are generally mild, manifested as upper and middle abdominal pain accompanied by diarrhea, with loose or watery stools as the main manifestation, and are effectively treated with antibiotics.

⑤ Yersinia infection of the small intestine and colon: The clinical manifestations are roughly similar to Campylobacter infection, and symptoms such as diarrhea are often milder.

⑥Intestinal Staphylococcus aureus infection: The onset is relatively acute, and symptoms may include chills, fever, abdominal pain and diarrhea. Diarrhea is mainly loose stools, which may be accompanied by a small amount of mucus, pus and blood. Stool culture can confirm the diagnosis. This disease often occurs after the use of broad-spectrum antibiotics, hormones or major surgical surgery. Stool culture may reveal Staphylococcus aureus.

⑦Acute hemorrhagic necrotizing enteritis: It is now generally believed to be related to infection with Clostridium perfringens or Clostridium difficile. The onset is acute, and symptoms such as abdominal pain and diarrhea are generally severe. The abdominal pain is severe and can spread throughout the abdomen. It can be continuous pain or paroxysmal. Early diarrhea may be loose or watery stools, more than 10 times a day, and may then contain blood. In severe cases, the stool may be bloody and watery, often accompanied by symptoms such as chills, fever, nausea and vomiting. This disease is more common in adolescents.

⑧ Pseudomembranous colitis: It occurs after long-term and excessive use of antibiotics, and can also occur in patients with compromised immune function. It is mostly caused by secondary intestinal infection with Clostridium difficile, the toxins of which damage the intestinal mucosa. The clinical characteristics are frequent bowel movements, which can reach more than 20 times a day in severe cases. The stool may contain mucus, pus and blood, or even bloody water. Sometimes egg-drop-like pseudomembranes may be discharged, often accompanied by fever, palpitations, dehydration, electrolyte imbalance, hypotension and other systemic poisoning symptoms. Pathogenic bacteria can be found when stool is cultured for anaerobic bacteria. Metronidazole, vancomycin, etc. are effective treatments.

⑨Cholera: caused by infection with Vibrio cholerae. The clinical manifestations vary in severity. In mild cases, the symptoms are relatively mild, often watery diarrhea, several times a day, and may be accompanied by nausea, vomiting, abdominal pain and other symptoms. In severe cases, the bowel movements are more frequent and the stools may be rice-soup-like. Patients often have fever, dehydration, hypotension and other symptoms of systemic poisoning. Stool culture can identify pathogenic bacteria.

(2) Protozoan and parasitic infections:

① Amebic dysentery: The onset is generally acute, with symptoms such as fever, abdominal pain and diarrhea. Diarrhea occurs several to more than 10 times a day, and the stool is accompanied by mucus, pus and blood. Sometimes the stool is dark red or jam-like, with a large amount and a foul odor. Examination of fresh stool can confirm the diagnosis if amebic trophozoites are found. Treatment is effective with metronidazole or tinidazole.

②Acute schistosomiasis: It usually occurs in people who are infected with a large number of schistosome cercariae for the first time. They often have symptoms such as chills, fever, abdominal distension, cough, abdominal pain and diarrhea. The diarrhea is not serious, ranging from 3 to 5 times a day, and can be loose stools or contain mucus. The number of eosinophils in peripheral blood increases. If the patient is infected repeatedly, he or she will often have symptoms such as hepatosplenomegaly.

③ Giardia lamblia infection: 3 to 5 bowel movements a day, mostly watery or loose stools, with little mucus. The diagnosis is confirmed by finding flagellates in the stool. Metronidazole is effective in treatment.

④ Trichomonas infection: Intestinal Trichomonas infection can also cause diarrhea, with bowel movements varying from several times a day, mainly loose stools, and may contain mucus.

(3) Viral infection: It is more common in intestinal rotavirus infection and intestinal adenovirus infection. The clinical symptoms are generally mild and may include abdominal pain, diarrhea, etc. The diarrhea may occur several times a day and is mainly loose or watery stools.

(4) Fungal infection: Long-term use of antibiotics, hormones or patients with chronic wasting diseases in the middle and late stages may develop fungal infections in the intestines, causing intestinal mucosal congestion, edema, erosion and ulcer formation, leading to diarrhea, manifested by increased frequency of bowel movements. In mild cases, the stool may be loose and soft with mucus, several times a day, and sometimes the stool may appear egg white-like. In severe cases, the stool may appear mucus, pus and blood. The diagnosis can be confirmed when the pathogenic fungus is found through routine stool examination or culture.

(5) Food poisoning:

① After eating food contaminated by Staphylococcus aureus, Salmonella, Halobacterium or Clostridium botulinum, symptoms such as fever, abdominal pain, vomiting, diarrhea and dehydration may occur, which is called food poisoning. The patient's stool may be loose or watery, often accompanied by mucus, and a few may contain pus and blood.

② Diarrhea may occur after taking poisonous mushrooms, puffer fish, large fish gallbladders and other toxic chemical poisons such as rat poison and pesticides. Diarrhea is mainly characterized by loose or watery stools, with little pus and blood, and may be accompanied by symptoms such as vomiting and abdominal pain. In addition to diarrhea, the above-mentioned poisons also have their own special symptoms.

(6) Allergic reactions: Food allergies (milk, fish, shrimp, seafood, etc.) can cause abdominal pain and diarrhea; diseases such as allergic purpura can be accompanied by increased intestinal motility and diarrhea. Diarrhea is often characterized by loose watery stools, often accompanied by abdominal pain.

(7) Drugs: A variety of drugs can cause diarrhea, such as erythromycin, magnesium hydroxide, neomycin, lincomycin, magnesium sulfate, sorbitol, mannitol, 5-fluorouracil, reserpine, propranolol, etc. The mechanisms by which these drugs cause diarrhea are different; certain chemicals such as phosphorus, arsenic, mercury and alcohol poisoning can all cause acute diarrhea. Diarrhea is often characterized by loose and watery stools, often without mucus, pus or blood.

2. Causes of chronic diarrhea There are many causes of chronic diarrhea, generally speaking, they can be divided into the following seven aspects. Since chronic diarrhea is more common in clinical practice, the characteristics of the related disease are briefly described to facilitate identification.

(1) Intestinal infection: It is the most common cause of chronic diarrhea.

① Bacterial infection:

A. Chronic bacillary dysentery: Acute bacillary dysentery may develop into a chronic disease if it is not completely cured, or it may present as an acute attack on the basis of a chronic disease, manifested by 3 to 5 bowel movements per day, which may be accompanied by mucus, pus and blood, and often with a feeling of tenesmus. A minority of patients have pain in the left lower abdomen. The positive rate of stool culture in chronic bacillary dysentery is low, generally only 15% to 30%, so repeated cultures are required to detect pathogenic bacteria.

B. Intestinal tuberculosis: more common in adolescents and middle-aged people, more common in women than in men. The disease is most likely to occur at the terminal ileum or the right colon. Diarrhea is the main symptom of ulcerative intestinal tuberculosis, which often alternates with constipation. Diarrhea is characterized by mushy or watery stools, which occur 3 to 5 times a day, and in severe cases more than 10 times a day, and is often accompanied by symptoms of tuberculosis poisoning such as fever and night sweats. Barium enema X-ray or colonoscopy can confirm the diagnosis.

② Protozoan and parasitic infections:

A. Chronic amoebic dysentery (also known as chronic amoebic enteritis): Stools are passed 3 to 5 times a day and are pasty and watery, and may be accompanied by mucus or blood. Typical jam-like stools are rare in chronic cases. The course of the disease can last for months or even years, with repeated acute attacks during the course of the disease. Amebic trophozoites can often be found in fresh feces after repeated attacks.

B. Chronic schistosomiasis: Patients with chronic schistosomiasis may suffer from diarrhea, 3 to 5 times a day, mostly loose stools, which may be accompanied by mucus or pus and blood. Patients often have manifestations of schistosomiasis-related liver fibrosis. The diagnosis is based on serum antibody testing and detection of eggs in stool or rectal mucosal biopsy.

C. Giardia lamblia or Trichomonas infection: Chronic cases have bowel movements several times a day, which are often loose or watery, sometimes with mucus. The diagnosis is confirmed by finding Giardia lamblia or Trichomonas in the stool.

③Chronic fungal enteritis: often occurs after long-term use of antibiotics and hormones, and is also prone to occur in the late stages of chronic wasting diseases. It manifests as diarrhea, accompanied by mucus or pus and blood in severe cases, and may recur. The diagnosis can be confirmed by finding fungi in the stool.

(2) Nonspecific or non-infectious intestinal inflammation:

1. Chronic nonspecific ulcerative colitis: It is generally considered to be an autoimmune disease. It has been on the rise in China in recent years and is more common in young and middle-aged people. The lesions mainly invade the rectum, sigmoid colon and descending colon, and may also invade the right colon. They can be divided into three types: mild, severe and fulminant. The light type is the most common. In mild cases, patients defecate 3 to 4 times a day, while in severe cases, the patient may defecate more than 10 times a day. The stool is pasty or loose, often mixed with mucus, pus and blood. In severe cases, only mucus, pus and blood are discharged without feces.

2. Chronic radiation enteritis: If patients with cervical cancer or pelvic malignancies develop diarrhea within weeks or months after radiotherapy, the possibility of radiation enteritis should be considered. The main symptoms are mucus and blood in the stool, often accompanied by tenesmus and local pain in the rectum. During colonoscopy, the diseased mucosa (mucosa damaged after radiotherapy) may be found to be congested, eroded, or bloody. This disease can persist for many years without recovery.

(3) Malabsorption syndrome: The classification of malabsorption syndrome is very complex. Malabsorption can be caused by stomach and small intestine diseases, or by liver, gallbladder, and pancreas diseases.

①Primary malabsorption:

A. Tropical steatorrhea: also known as tropical sprue, occurs in tropical areas. The cause is still unknown. It is generally believed to be related to protein, folic acid and B vitamins deficiency. The diarrhea is characterized by large amounts of foul-smelling stool, and about one-third of patients present with steatorrhea.

B. Non-tropical steatorrhea: also known as gluten enteropathy, primary steatorrhea or celiac disease. The patient's intestinal mucosa lacks a peptide-degrading enzyme, so it cannot break down the toxic alpha-glutenin, which damages the intestinal villi and intestinal epithelial cells, ultimately leading to malabsorption. The diarrhea is characterized by fatty diarrhea, with large amounts of greasy stools, a foul odor, and bowel movements occurring several times a day.

②Secondary malabsorption:

A. After gastrectomy: more common after total gastrectomy and Billroth II surgery. Because food enters the small intestine quickly, the secretion of enterokinase, pancreatic digestive enzymes and bile is insufficient, or the pancreatic juice and bile are not mixed sufficiently with food, which can cause malabsorption and cause diarrhea. In addition, if bacterial overgrowth (blind loop syndrome) occurs after gastrointestinal surgery, the bacterial decomposition and binding of bile salts will affect the formation of microparticles, which can lead to steatorrhea.

B. Chronic hepatobiliary diseases: such as chronic hepatitis, cirrhosis, and intrahepatic and extrahepatic bile duct obstruction, can cause steatorrhea due to the lack of bile salts, which prevents fat from emulsification and transport.

C. Small intestinal disease: Excessive small intestinal resection (for example, when more than 75% of the total length of the small intestine is removed or only 120 cm remains, it is called short bowel syndrome), gastric-colonic fistula or gastric-ileal fistula can all lead to diarrhea due to the reduction of the absorption area of ​​the small intestine, or food can go directly to the colon through the fistula without passing through the small intestine or jejunum.

D. Chronic pancreatic diseases: such as chronic pancreatitis, pancreatic cancer, etc., may cause diarrhea due to insufficient pancreatic juice secretion and lack of pancreatic enzymes, resulting in fat and protein digestion and absorption disorders.

E. Diffuse lesions of the small intestinal mucosa: such as malignant lymphoma of the small intestine and Whipple's disease, all of which cause steatorrhea due to damage to the small intestinal mucosa and dilation or obstruction of the lymphatic vessels. In the case of scleroderma, atrophy of the gastrointestinal mucosa and submucosa may eventually cause digestion and absorption disorders and lead to diarrhea.

(4) Endocrine diseases: Many endocrine diseases are accompanied by symptoms of diarrhea. Patients may sometimes first visit the gastroenterology department due to diarrhea, so they must be differentiated.

① Hyperthyroidism: 10% to 15% of hyperthyroidism patients experience diarrhea, but the diarrhea is generally not severe, occurring several times a day, mostly loose or watery stools, without mucus, pus or blood, and rarely with abdominal pain. Patients often experience symptoms such as sweating, palpitations, weight loss, enlarged thyroid gland, and exophthalmos.

② Diabetes: The cause of diarrhea is related to pancreatic exocrine dysfunction and abnormal intestinal motility. Diarrhea may be soft stools or watery stools, or it may be fatty diarrhea, often without mucus, pus or blood, and may occur several times a day. A small number of patients may present with persistent diarrhea.

③Hypoparathyroidism and medullary thyroid tumor: The former can cause diarrhea due to increased neuromuscular irritability caused by low blood calcium, but the diarrhea is generally not serious, ranging from 2 to 3 times a day. The latter is caused by the release of calcitonin by the tumor, which leads to diarrhea.

④ Adrenal insufficiency: When the adrenal cortex function is low, it can cause a decrease in the secretion of gastric acid and pepsin, and is often accompanied by small intestinal absorption dysfunction, so diarrhea may occur, which is often mushy and not very frequent.

⑤ Pancreatic cholera syndrome: This disease is rare, with sporadic case reports in China. This disease is caused by abnormal secretion of vasoactive intestinal peptide (VIP) by tumor cells. Some people believe that VIP in adult patients mostly comes from islet cell tumors, while VIP in children mostly comes from ganglioneuroma or ganglioneuroma. The clinical features of this disease are watery diarrhea, hypokalemia and true achlorhydria (domestic cases reported include patients with normal gastric acid secretion). The diagnosis must be confirmed by VIP measurement, B-ultrasound, CT or MRI examination to detect the tumor.

⑥Gastrinoma: It is caused by pancreatic non-beta cell tumors secreting a large amount of gastrin. A large amount of gastrin stimulates the parietal cells to secrete a large amount of gastric acid. Diarrhea is related to the secretion of a large amount of gastric acid and gastric juice. This disease is often accompanied by the formation of multiple ulcers in the stomach and duodenum. The diagnosis requires gastric juice analysis, gastrin level measurement, and ultrasound, CT or MRI examinations to detect tumors (most tumors are located in the pancreatic tissue, and a few are located in other parts of the abdominal cavity).

(5) Neoplastic diseases: benign or malignant tumors.

① Gastrointestinal malignant lymphoma: The most vulnerable part of gastrointestinal lymphoma is the ileum, while the colon is less affected. In addition to diarrhea, it is often accompanied by abdominal pain or abdominal mass, and in a few patients, bloody stools may be the main symptom.

②Carcinoid syndrome: Diarrhea is related to the large amount of vasoactive substances such as 5-hydroxytryptamine, bradykinin and serotonin secreted by carcinoid cells. The most common site of carcinoid occurrence is the appendix, but it can also occur in other parts of the intestine. In addition to diarrhea, patients often have paroxysmal redness of the skin on the face, neck, or upper body, and a few also have symptoms of bronchial asthma.

③Colon cancer: Middle and late stage rectal or sigmoid colon cancer may cause mucus, pus and blood in the stool, accompanied by left lower abdominal pain and tenesmus. Diarrhea is an important symptom of right-sided colon cancer, often manifested as loose or mushy stools, without obvious mucus, pus or blood (but red blood cells and pus cells are often present under the microscope). Patients usually have abdominal pain, weight loss and anemia. The main manifestation of left-side colon cancer is constipation or chronic intestinal ileus, but if it is accompanied by infection or cancer rupture, it may present with bloody stools.

④ Intestinal adenomatous polyps or polyposis: secretory diarrhea may occur due to bleeding, erosion or ulceration on the surface of polyps. In addition to diarrhea, bloody stools are also one of the important symptoms of intestinal polyps.

(6) Gastrointestinal dysfunction: i.e. irritable bowel syndrome . IBS is a group of intestinal dysfunction syndromes consisting of abdominal discomfort or pain accompanied by abnormal defecation. The patients have no organic lesions or abnormal biochemical indicators in their intestines. What was previously called mucous colitis, irritable colon or allergic colitis are now collectively referred to as IBS. The occurrence of this disease is often closely related to mental stress and emotional excitement, that is, mental and psychological factors have an important influence on the onset of the disease. In addition, stress and/or intestinal infection (such as dysentery, enteritis, etc.) are often important triggers of IBS. In recent years, the pathogenesis of IBS has been studied in depth. It is believed that IBS is characterized by abnormal visceral sensation and increased sensitivity of the colon to stimulation, which leads to abnormal bowel movements (diarrhea or constipation or alternating diarrhea and constipation). In 2000, the latest diagnostic criteria for IBS, the Rome II criteria, were promulgated internationally. The key points are:

① Diagnosis: This disease first needs to rule out the explanation of symptoms by tissue structure or biochemical abnormalities.

② Recurrent abdominal pain or discomfort accompanied by 2 of the following 3 abnormal bowel movements for at least 3 months within 1 year.

A. Abdominal pain after defecation is relieved or alleviated.

B. Abnormal bowel movement frequency (i.e. 3 times/day or 3 times/week).

C. Abnormal stool shape (loose stool or dry, hard stool). The Rome II criteria are gradually being accepted by gastroenterologists in many countries. Patients with diarrhea-type IBS often experience diarrhea after abdominal pain or discomfort. The abdominal pain or discomfort is relieved or alleviated after defecation. The stool is characterized by loose and soft stools, and a few are watery. The number of times a day varies, often more than 3 times. The stool does not contain pus or blood, and a few may be accompanied by mucus. Diagnosed in traditional Chinese medicine as "early morning diarrhea", it can be considered a manifestation of IBS. Patients often experience abdominal pain or discomfort before dawn, most of them have hyperactive bowel sounds, and the pain is relieved or alleviated after the abdominal pain. Generally, they have diarrhea 2 to 3 times before breakfast, and the diarrhea often stops after breakfast. A small number of patients are prone to abdominal pain and diarrhea after each meal. This is because the gastro-colonic hyperreflexia is caused after eating, that is, after the stomach contains food, it causes hyperperistalsis of the colon. The patient has abdominal pain or discomfort, followed by the urge to defecate. This symptom should also be considered to be caused by colon dysfunction.

(7) Other factors:

① Intestinal flora imbalance: Diarrhea is mostly caused by long-term use of broad-spectrum antibiotics, which causes imbalance of normal intestinal flora. In severe cases, it can induce pseudomembranous enterocolitis.

② Uremia: Diarrhea caused by uremic enteritis, with 3 to 5 bowel movements per day, mostly mushy or watery stools.

The above are the reasons for diarrhea. We can see that there are many reasons for diarrhea. When we have diarrhea due to physical discomfort, we cannot simply think that we have a gastrointestinal disease just because of diarrhea. This is a very incorrect approach. At this time, we should go to the hospital for examination and treatment in time.