Secretory Diarrhea

Secretory Diarrhea

Definition

• Secretory diarrhea occurs when a stimulating substance increases secretion or decreases absorption of large amounts of water and electrolytes.

Causes

• Vasoactive Intestinal Peptide (VIP): Secreted from pancreatic tumors.

• Unabsorbed Dietary Fat: Leads to steatorrhea.

• Laxatives: Stimulate secretion.

• Hormones: Such as secretion that increase gut fluid.

• Bacterial Toxins: Induce excess secretion.

• Excessive Bile Salts: Cause increased fluid secretion.

Mechanism

• Many agents stimulate intracellular cyclic adenosine monophosphate (cAMP) and inhibit Na+/K+-adenosine triphosphatase (ATPase), leading to increased secretion.

• Simultaneous inhibition of ion absorption often occurs.

Characteristics

• Recognized by:

  • Large stool volumes (>1 L/day)

  • Normal ionic content

  • Osmolality approximately equal to plasma

• Fasting Effect: Does not alter stool volume.