What Is Secretory Diarrhea?

Secretory diarrhea refers to diarrhea caused by intestinal mucosa irritation resulting in excessive secretion of water or electrolytes or inhibition of absorption.

Secretory diarrhea

Secretory diarrhea concept

Secretory diarrhea refers to diarrhea caused by intestinal mucosa irritation resulting in excessive secretion of water or electrolytes or inhibition of absorption.

Mechanism of secretory diarrhea

The mechanism of secretory diarrhea involves many factors. Among them, cyclic adenosine monophosphate (cAMP) plays an important role. CAMP in intestinal mucosa cells induces secretion of electrolytes and water. CAMP needs to undergo intracellular adenylate cyclization. Enzyme catalysis works. Enterotoxin (a type of exotoxin) secreted by Vibrio cholerae can quickly bind to jejunal epithelial cells, stimulate adenylate cyclase, increase the intracellular cAMP content, and accelerate the process of water and electrolyte secretion into the intestinal cavity. When the small intestinal secretion exceeds its absorption capacity, diarrhea occurs.

Diarrhea caused by cholera is a typical example of simple secretory diarrhea.

Another toxin secreted by pathogenic E. coli can also cause cholera-like watery diarrhea, and its pathogenesis may be similar to that of Vibrio cholerae.

Diarrhea caused by eating foods contaminated by bacteria such as staphylococci may also belong to this type of diarrhea.

Diarrhea caused by vasoactive intestinal peptide tumors (VIP tumors) is a non-infectious, secretory diarrhea. VIP released from tumors can activate adenylate cyclase in the intestinal mucosa and stimulate small intestine secretion, resulting in cholera-like severe Watery diarrhea, often accompanied by severe hypokalemia and metabolic acidosis, is also known as pancreatic cholera.

Gastrinoma can secrete a large amount of gastrin, which stimulates the parietal cells of the intestinal mucosa to secrete a large amount of gastric acid. After the gastric acid enters the small intestine, it accelerates intestinal peristalsis and causes watery diarrhea. It is also a secretory diarrhea.

The factors that stimulate the secretion of intestinal mucosa can be divided into four categories: enterotoxin of bacteria, such as toxins of Vibrio cholerae, Escherichia coli, Salmonella, etc .; neurohumoral factors, such as vasoactive intestinal peptide (VIP), serotonin, calcitonin immune inflammatory mediators, such as prostaglandin, leukotriene, platelet activating factor, tumor necrosis factor, interleukin, etc .; detergents, such as bile salts and long-chain fatty acids, stimulate the secretion of anions and increase the mucosal epithelium. Permeability causes secretory diarrhea.

Misunderstanding of secretory diarrhea

Misunderstanding 1: Blind use of diarrhea remedies for diarrhea

Most diarrhea is caused by unclean diet, and secretory diarrhea is also very common. So when many people have diarrhea, they will take it for granted that it is caused by bad stomach, so they will take medicine by experience. Pull up stomach remedies. There are many reasons for diarrhea. Treating diarrhea with diarrhea remedies without authorization can easily fall into the misunderstanding of treatment and aggravate the condition.

Myth 2: Blind diarrhea with antibiotics

Many patients not only like to use diarrhea remedies to treat diarrhea, they also like to use antibiotics to treat diarrhea. Although antibiotics can kill pathogenic microorganisms, they can also kill the normal flora in the intestine, causing disturbances in the intestinal flora and imbalance of the intestinal environment, leading to the conversion of acute diarrhea to chronic diarrhea. In addition, antibiotics are often used to treat diarrhea, which will make the body resistant to antibiotics, so patients should not use antibiotics to treat diarrhea without authorization. If the condition is serious, it is necessary to use antibiotics, and they should be used with caution under the guidance of a doctor. ^[1]

Clinical characteristics of secretory diarrhea

The clinical features of secretory diarrhea are:

(1) discharge a large amount of watery feces, which can reach several liters per day;

(2) Feces contain a large amount of electrolyte, and its osmotic pressure is basically the same as that of plasma;

(3) pus and blood are not contained in the stool;

(4) Diarrhea does not stop after fasting;

(5) Generally no abdominal pain;

(6) Histological examination of the intestinal mucosa is basically normal.

Etiology and pathology of secretory diarrhea

^[2] Secretory diarrhea is caused by the intestinal and colonic secretion of salts and water in excess of their absorption capacity. Substances that stimulate the intestinal tract include bacterial toxins (such as cholera), enteroviruses, bile acids (such as after ileum resection), unabsorbed food fats (such as when having fatty diarrhea), and certain drugs (such as anthraquinone diarrhea). Agents, castor oil, prostaglandins) and peptide hormones (such as intestinal vasoactive peptides from pancreatic tumors). Colitis (collagenous or lymphocytic colitis) under the microscope accounts for 5% of secretory diarrhea.

Diseases that cause secretory diarrhea

There are five main categories of diseases that cause secretory diarrhea:

1. Abnormal media Various abnormal media can activate cAMP on the small and large intestine cell membranes, the intracellular cAMP content increases sharply, which increases the cytoplasmic calcium ion content, leading to increased intestinal secretion, a large amount of water, sodium bicarbonate, chloride and potassium ions Lost. These mediators include bacterial enterotoxin, gastrointestinal polypeptides (vasoactive intestinal peptide, gastrin, substance P, calcitonin, etc.) secreted by tumor pathologically secreted by amine precursor uptake and decarboxylation (APUD) tumors, Prostaglandins, serotonin, etc. Enterotoxins can be produced in vitro and then ingested (such as food poisoning), or they can be produced in the body by bacteria. The effects of enterotoxins are generally independent of the presence of bacteria, so symptoms can be self-limiting. Seen in acute food poisoning or intestinal infections, the most typical example is cholera. Vasoactive intestinal peptide tumors (VIP tumors) secrete a large amount of VIP, which promotes the secretion of water and electrolytes such as Na +, K +, and C1- in the jejunum, ileum, and colon, resulting in watery diarrhea. Radiation from refrigerator appliances, sunlight, vegetables, air, etc. can also cause diarrhea.

2. Endogenous or exogenous cathartic substances such as bile acid, fatty acids, some laxatives, etc. Normal human bile acid is synthesized in the liver and enters the intestinal cavity with bile. Most of it is absorbed in the ileum and returns to the liver (intestinal liver circulation). The daily output of bile acid from feces is only about 500 mg. During extensive ileal disease, ileal resection or bypass, bile acid reabsorption occurs and enters the colon, stimulating colon secretion and causing secretory diarrhea. Colonic stimulation of excess fatty acids is also one of the causes of secretory diarrhea. Pathological conditions that cause an increase in fatty acids in the intestinal lumen include short bowel syndrome and fat malabsorption caused by pancreatic and small bowel disease. Laxatives such as senna and phenolphthalein can also stimulate colon secretion and lead to diarrhea.

3 Intestinal lymphatic drainage disorders are widespread small intestinal lymphoma, intestinal tuberculosis, Crohn disease, etc.

4 Secretory rectal or sigmoid chorionic adenoma.

5. Congenital chloride diarrhea (C1-: HCO3 exchange system defect) and congenital sodium diarrhea (Na +: H + exchange system defect). Secretory diarrhea has the following characteristics: the daily stool volume exceeds 1L (up to 10L or more); the stool is watery, without pus and blood; the plasma-fecal permeability difference is <50mmol / L H2O, which is mainly due to the stool The intestine is excessively secreted, and its electrolyte composition and osmotic pressure are very close to plasma; pH of stool is mostly neutral or alkaline; Diarrhea persists after fasting for 48 hours, and stool volume is still greater than 500ml / 24h.