What is the difference between osmotic and secretory diarrhea

Fecal electrolyte levels can be used to distinguish secretory from osmotic diarrhea. Although fecal pH tests and fecal electrolyte levels are helpful, they are often omitted from the initial workup. Abnormal laboratory results help distinguish organic from functional disease. Travel risk factors might warrant a stool culture and sensitivity test, stool ova and parasite examination, and Giardia and Cryptosporidium stool antigen tests.

Giardia and Cryptosporidium infections are easily missed on routine ova and parasite examination, although stool acid-fast staining identifies Cryptosporidium. Finally, sigmoidoscopy or colonoscopy is often required to establish a specific diagnosis.

Microscopic colitis can be diagnosed only by colon biopsy. It is usually impractical to test and treat the many possible causes of chronic diarrhea. In most cases, it is more reasonable to categorize by type of diarrhea before testing and treating to narrow the list of diagnostic possibilities and reduce unnecessary testing. Information from references 1 and Empiric therapy may be justified if a specific diagnosis is strongly suspected or resources are limited.

Life-threatening conditions should be excluded. A trial of metronidazole Flagyl for malabsorption in a traveler would cure possible giardiasis. Likewise, an empiric trial of bile acid resins can help confirm bile acid malabsorption. Irritable bowel syndrome IBS is the most common cause of functional diarrhea in the developed world. IBS is a symptom complex of crampy abdominal pain accompanied by altered bowel habits, either with diarrhea or constipation.

Usually watery diarrhea occurs while awake, often following meals. Discomfort is alleviated by defecation, and stool mucus is noted in one-half of patients. IBS is exacerbated by emotional stress or eating, but it may also be a response to recent infection. IBS symptoms subsequent to a bout of traveler's diarrhea postinfectious IBS may take months to resolve, despite a negative workup.

Screening for celiac disease and iron deficiency anemia is recommended, but routine colonoscopy is not cost-effective unless alarm symptoms are present. Symptoms of recurrent abdominal pain or discomfort and a marked change in bowel habits for at least six months, with symptoms experienced on at least three days per month for at least three months.

Two or more of the following must apply:. Pain is relieved by a bowel movement. Onset of pain is related to a change in frequency of stool. Onset of pain is related to a change in appearance of stool. Information from references 12 and IBD may manifest as ulcerative colitis or Crohn disease. Both often involve blood and pus in the stool, with onset between 15 and 40 years of age. Early cases are often confused with IBS, but symptoms inevitably progress. Early ulcerative colitis, distal colitis, and proctitis result in episodes of rectal bleeding, diarrhea, pain, and tenesmus.

Moderate left-sided and severe extensive colitis are associated with bloody diarrhea, weight loss, fever, and anemia. Crohn disease typically causes an ileitis but later affects the entire gastrointestinal tract to become exudative. Early symptoms can be subtle, leading to a long delay in diagnosis. Abdominal pain, diarrhea, fever, perianal fistulae, and stools positive for blood are common, although bloody diarrhea is unusual.

The diagnosis of IBD is usually supported by colonoscopy. Laboratory testing should include a complete blood count, fecal leukocyte level, erythrocyte sedimentation rate, and fecal calprotectin level. In adults, fecal calprotectin level is 93 percent sensitive and 96 percent specific for IBD, although specificity is less 76 percent in children and teenagers.

Faecal calprotectin for screening of patients with suspected inflammatory bowel disease: diagnostic meta-analysis. Microscopic colitis is characterized by intermittent, secretory diarrhea in older patients, although persons of all ages can be affected. It is thought to be fairly common, comprising 10 percent of chronic diarrhea cases.

Colonoscopy is normal, but biopsy from the transverse colon confirms the diagnosis. Two histologic patterns are found: lymphocytic colitis lymphocytic infiltrate of the lamina propria and collagenous colitis in which the subepithelial collagen layer is also increased to more than 10 mm. Malabsorptive and maldigestive diarrhea result from impaired nutrient absorption and impaired digestive function, respectively. Celiac disease gluten-sensitive enteropathy , intestinal bypass, mesenteric ischemia, small bowel bacterial overgrowth, Whipple disease, and giardiasis can all cause loss of absorptive capacity.

Absent pancreatic enzymes or bile acids can cause maldigestion. Classic symptoms include abdominal distention with foul-smelling, large, floating, pale, fatty stools steatorrhea and weight loss. Celiac disease or sprue is small intestine malabsorption provoked by gluten wheat ingestion in genetically susceptible patients, often of European descent. It is suspected that diagnosed celiac disease cases represent only a fraction of patients with this condition. Patients most commonly present with chronic diarrhea, fatigue, iron deficiency anemia, and weight loss, but this classic constellation is often absent.

A positive celiac panel, typically consisting of immunoglobulin A IgA antigliadin, antiendomysium, and antitissue transglutaminase antibodies, is usually followed by duodenal biopsy for confirmation. Testing should be expanded to include all patients with unexplained chronic diarrhea, IBS, iron deficiency anemia, chronic fatigue, weight loss, infertility, and elevated liver transaminase levels.

Symptomatic patients with type 1 diabetes mellitus and thyroid disease should be tested, because these conditions may predispose to celiac disease. Most microbial gastrointestinal infections cause acute self-limited diarrhea, but others persist, resulting in inflammation invasive bacteria and parasites or occasionally malabsorption giardiasis. A history of travel and antibiotic use is important. Bacterial causes include Aeromonas , Campylobacter , C.

Parasitic diarrhea may be caused by Cryptosporidium, Cyclospora , Entamoeba , Giardia , Microsporida, and Strongyloides. Giardia , the most common of these, is best diagnosed with fecal antigen testing. The suspected infectious agent has never been identified. This gram-positive anaerobic bacillus is easily spread through ingestion of spores, rapidly colonizing the colon following antibiotic therapy.

A history of using fluoroquinolones, clindamycin, penicillins, or cephalosporins in the past three months is often associated.

Proton pump inhibitors and IBD further increase the risk of C. Because IBD and C. A new hypervirulent C. Colonoscopy is unnecessary with a positive stool toxin. Although C. Laxatives, antacids, proton pump inhibitors, and antineoplastic agents are medications that can lead to diarrhea; other examples of drugs associated with diarrhea are listed in Table 3. Diarrhea may be osmotic from magnesium, phosphates, sulfates, or sorbitol or secretory following use of stimulant laxatives.

Symptoms resolve when the offending agent is eliminated. Pseudomembranous colitis Clostridium difficile. Information from reference 2. Endocrine causes of chronic secretory diarrhea include Addison disease, carcinoid tumors, vipoma, gastrinoma Zollinger-Ellison syndrome , and mastocytosis.

Hyperthyroidism increases motility. Serum peptide concentrations e. Common causes of chronic diarrhea are listed in Table 4. Chronic malabsorptive diarrhea, fatigue, iron deficiency anemia, weight loss, dermatitis herpetiformis, family history.

Immunoglobulin A antiendomysium and antitissue transglutaminase antibodies most accurate; duodenal biopsy is definitive. Fecal leukocyte level; enzyme immunoassay that detects toxins A and B; positive fecal toxin assay; sigmoidoscopy demonstrating pseudomembranes.

Osmotic e. Thyroid-stimulating hormone level, serum peptide concentrations, urinary histamine level. Infectious enteritis or colitis diarrhea not associated with C. Bloody inflammatory diarrhea, abdominal pain, nausea, vomiting, loss of appetite, family history, eye findings e.

Complete blood count, fecal leukocyte level, erythrocyte sedimentation rate, fecal calprotectin level. Stool mucus, crampy abdominal pain, altered bowel habits, watery functional diarrhea after meals, exacerbated by emotional stress or eating. Already a member or subscriber? Log in. Interested in AAFP membership? Learn more. Reprints are not available from the authors.

AGA technical review on the evaluation and management of chronic diarrhea. Philadelphia, Pa. Schiller L, Sellin J. Whitehead WE. Diagnosing and managing fecal incontinence: if you don't ask, they won't tell. Rodrigo L. World J Gastroenterol. Nelson DA Jr. Gluten-sensitive enteropathy celiac disease : more common than you think. Am Fam Physician. Stool composition in factitial diarrhea: a 6-year experience with stool analysis.

Ann Intern Med. Chronic diarrhea with normal stool and colonic examinations: organic or functional? J Clin Gastroenterol. Collagenous and lymphocytic colitis: evaluation of clinical and histological features, response to treatment, and long-term follow-up.

Am J Gastroenterol. Schiller LR. Chronic diarrhea. Evaluation and management of chronic diarrhea: An algorithmic approach. Other symptoms you might experience are:. Osmotic diarrhea can also have severe symptoms. See your doctor immediately if you have symptoms such as:.

Osmotic diarrhea results when you eat foods that, instead of being absorbed, draw water into your intestine. Osmotic diarrhea often lasts a few days. It generally responds to simple home treatments including diet adjustment and over-the-counter OTC medications such as loperamide Imodium and bismuth subsalicylate Kaopectate, Pepto-Bismol.

There are changes you can make to your diet to potentially treat osmotic diarrhea. Doctors suggest limiting or avoiding the following foods:. In addition to checking with your doctor before taking any antidiarrheal medicine , you should also make an appointment if:.

Osmotic diarrhea is caused by eating certain kinds of food and usually lasts only a few days. It typically goes away once you stop consuming the offending food.

Many people address their diarrhea with OTC medicine and a diet change. If it lasts more than a few days or symptoms become more severe, a visit with your doctor is strongly suggested. Discover the causes of nocturnal diarrhea and how to treat it. Explosive or severe diarrhea usually resolves on its own with self-care. Large volumes of water are normally secreted into the small intestinal lumen, but a large majority of this water is efficienty absorbed before reaching the large intestine.

Diarrhea occurs when secretion of water into the intestinal lumen exceeds absorption. Many millions of people have died of the secretory diarrhea associated with cholera. The responsible organism, Vibrio cholerae , produces cholera toxin, which strongly activates adenylyl cyclase , causing a prolonged increase in intracellular concentration of cyclic AMP within crypt enterocytes. This change results in prolonged opening of the chloride channels that are instrumental in secretion of water from the crypts , allowing uncontrolled secretion of water.

Additionally, cholera toxin affects the enteric nervous system , resulting in an independent stimulus of secretion. Exposure to toxins from several other types of bacteria e. In addition to bacterial toxins, a large number of other agents can induce secretory diarrhea by turning on the intestinal secretory machinery, including:. The epithelium of the digestive tube is protected from insult by a number of mechanisms constituting the gastrointestinal barrier , but like many barriers, it can be breached.

Disruption of the epithelium of the intestine due to microbial or viral pathogens is a very common cause of diarrhea in all species.