What is the Difference Between Osmotic and Secretory Diarrhea

The key difference between osmotic and secretory diarrhea is that osmotic diarrhea usually happens when an unabsorbed substance or solutes from food prevents normal water absorption in the intestine, while secretory diarrhea happens when too much water is secreted in the lumen of the small intestine for the body to absorb.

Diarrhea is the passing of loose, watery, or more frequent stools than normal. Generally, diarrhea is categorized into three basic groups: inflammatory, watery, and fatty diarrhea. Moreover, watery diarrhea is further categorized into osmotic, secretory, and functional diarrhea.

1. Overview and Key Difference
2. What is Osmotic Diarrhea
3. What is Secretory Diarrhea
4. Similarities – Osmotic and Secretory Diarrhea
5. Osmotic vs Secretory Diarrhea in Tabular Form
6. Summary – Osmotic vs Secretory Diarrhea

What is Osmotic Diarrhea?

Osmotic diarrhea occurs when too many solutes in the food we eat stay in the intestine, which prevents water absorption. This excess water causes bowel movements to be loose. The substances and food that increase the chances of osmotic diarrhea may include laxatives containing lactulose and citrate of magnesia, milk and other dairy products that have lactose, and excessive amounts of vitamin C or sorbitol. It can also be caused by certain antibiotics, certain blood pressure medications, laxatives that contain sodium phosphate, magnesium sulfate, and magnesium phosphate, chemotherapy, high-dose radiation therapy, and gallbladder removal.

The symptoms of osmotic diarrhea include stomach pain, bloating, nausea, blood or pus in the stool, stool having the color of tar, high fever, and dehydration. Moreover, osmotic diarrhea can be diagnosed through physical examination and blood tests. The treatment options for osmotic diarrhea include over-the-counter medications (Ioperamid and bismuth subsalicylate), limiting certain foods such as lactose-rich food like dairy products, sugar, artificial sweeteners, alcohol, coffee, carbonated drinks, legumes, vegetables high in dietary fiber like broccoli, nuts, and seeds, whole wheat, and consuming bread products from refined white flour, white rice, cooked vegetables, bananas, apple sauce, baked chicken with no skin, and boiled potatoes without skin.

What is Secretory Diarrhea?

Secretory diarrhea is a type of watery diarrhea that occurs when too much water is secreted in the lumen of the small intestine for the body to absorb. The possible causes of secretory diarrhea include intestinal peptide tumors, medications for asthma and cardiovascular disease, antidepressants, and ingestion of arsenic-containing compounds and pesticides. The signs and symptoms of this condition may include feeling bloated, feeling nausea and vomiting, fecal incontinence or inability to control bowel movements, and dehydration.

Moreover, secretory diarrhea can be diagnosed through medical history, physical examination, laboratory cultures, and blood tests. Furthermore, treatment options for secretory diarrhea may include intravenous rehydration, replacement of deficits, maintenance therapy, management of other abnormalities (metabolic acidosis, hypernatremia, hyponatremia, hypokalemia, hypocalcemia, and hypomagnesemia), and antidiarrhoeal agents like Ioperamide, diosmectite, octreotide, diphenoxylate, and oral bismuth.

What are the Similarities Between Osmotic and Secretory Diarrhea?

Osmotic and secretory diarrhea are two different types of watery diarrhea.
Both conditions are characterized by loose bowel movements and dehydration.
They can cause electrolyte abnormalities.
Both conditions can be diagnosed through physical examination and blood tests.
They are treated with lifestyle changes and antidiarrhoeal medications.

What is the Difference Between Osmotic and Secretory Diarrhea?

Osmotic diarrhea usually occurs when an unabsorbed substance or solutes from food prevents normal water absorption in the intestine, while secretory diarrhea occurs when too much water is secreted in the lumen of the small intestine for the body to absorb. Thus, this is the key difference between osmotic and secretory diarrhea. Furthermore, osmotic diarrhea is not common in Vibrio cholera infection, while secretory diarrhea is more common in Vibrio cholera infection.

The below infographic presents the differences between osmotic and secretory diarrhea in tabular form for side-by-side comparison.

Summary – Osmotic vs Secretory Diarrhea

Osmotic and secretory diarrhea are two different types of watery diarrhea that are characterized by loose bowel movements and dehydration. Osmotic diarrhea usually happens when unabsorbed substances or solutes from food prevent normal water absorption in the intestine. Therefore, it happens when the person consumes a nonabsorbable, osmotically active substance. In contrast, secretory diarrhea occurs when too much water is secreted in the lumen of the small intestine for the body to absorb. Therefore, it happens when electrolyte absorption is impaired. So, this summarizes the difference between osmotic and secretory diarrhea.

Reference:

1. Frothingham, Scott. “Osmotic Diarrhea: Symptoms, Causes, Treatments.” Healthline, Healthline Media, 11 May 2018.
2. Thiagarajah, Jay R, et al. “Secretory Diarrhoea: Mechanisms and Emerging Therapies.” Nature Reviews. Gastroenterology & Hepatology, U.S. National Library of Medicine, Aug. 2015.