Secretory diarrhea

Sx

watery; nl osmotic gap, no Δ diarrhea w/ fasting, nocturnal, cramps

Watery diarrhea with normal osmotic gap and no change with fasting, nocturnal, and cramps - A type of diarrhea characterized by frequent and watery stools, with a normal osmotic gap (indicating normal absorption of substances in the intestine) and no change in frequency with fasting. It is also characterized by occurrence at night and presence of cramps.

This pattern of symptoms suggests that the cause of the diarrhea may be due to factors such as irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), food intolerance, or infections.

• Caused by secretion of anions or K+ into lumen or inhib of Na absorption → ↑ H2O in stool. Most commonly caused by bacterial toxins from infxn (see above). Other causes:

• Endocrine: Addison’s, VIPoma, carcinoid, Zollinger-Ellison, mastocytosis, hyperthyroid (↑ motility). ✓ serum peptide levels (eg, gastrin, calcitonin, VIP) & urinary histamine.

• GI neoplasm: carcinoma, lymphoma, villous adenoma

• Microscopic colitis: common cause of chronic diarrhea w/ obscure origin. Often seen in middle-aged women w/ autoimmune disorders. NSAIDs, SSRIs, PPIs notable triggers. Grossly normal on colo but bx shows lymphocytic & plasmacytic infiltration of mucosa ± thickened submucosal collagen. Rx: budesonide (1st line), antidiarrheals, cholestyramine, bismuth; consider anti-TNFs if refractory (Gastro 2016;150:242).

• Bile acid-induced diarrhea: ileal resection or disease (eg, Crohn’s) → bile acids in colon → electrolyte & H2O secretion. Rx w/ empiric bile-acid binders (eg, cholestyramine).

因膽汁酸所導致的腹瀉：腸道切除手術或疾病（例如，克羅恩氏病）→腸道內的膽汁酸→離子與水的分泌。預防藥物為膽汁酸結合劑（例如，克拉司地酸鈉）