Chronic diarrhea pathophysiology
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Chronic diarrhea Microchapters |
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Diagnosis |
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Treatment |
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Case Studies |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Omodamola Aje B.Sc, M.D. [2]
Overview
The fundamental pathophysiology of all diarrhea is incomplete absorption of water from the lumen either because of a reduced rate of net water absorption (related to impaired electrolyte absorption or excessive electrolyte secretion) or because of osmotic retention of water intraluminally.[1] The causes of chronic diarrhea include inflammatory, osmotic, secretory, iatrogenic, motility, and functional diseases. In general, no single cause of chronic diarrhea is truly unifactorial from a perspective of pathophysiology.
Pathogenesis
Diarrhea is a condition of altered intestinal water and electrolyte transport. The physiological mechanisms of diarrhea include osmotic, secretory, inflammatory, altered motility or iatrogenic.
- Osmotic chronic diarrhea: It involves an unabsorbed substance that draws water from the plasma into the intestinal lumen along osmotic gradients.
- Chronic diarrhea due to an osmotic cause include osmotic laxatives such as lactose intolerance[2] antacids, fructose, lactulose, laxatives magnesium, phosphate, and sorbitol.
- Maldigestion syndromes such as disaccharidase deficiency and pancreatic exocrine insufficiency can also result in osmotic chronic diarrhea.
- Osmotic diarrheas might result in steatorrhea and azotorrhea (passage of fat and nitrogenous substances into the stool), but typically they do not cause any rectal bleeding.[3]
- Secretory chronic diarrhea results from disordered electrolyte transport and, despite the term, is more commonly caused by decreased absorption rather than net secretion.
- Secretory diarrheas include congenital abnormalities such as congenital chloridorrhea, in which an abnormality in the genetic control of chloride-bicarbonate exchange in the ileum results in the loss of chloride into the stool.
- Another example is the loss of α2-adrenergic function in enterocytes of patients with autonomic neuropathy caused by diabetes mellitus.
- The typical features of secretory diarrhea include the persistence of the diarrhea with fasting and the absence of steatorrhea, azotorrhea, or blood per rectum.
- Secretory diarrheas caused by neuroendocrine tumors has been identified by measurement of plasma levels of the hormone or its metabolite in the urine.
- Examples include measurements of VIP, gastrin, or calcitonin in plasma or 24-hour collections of urine for 5-hydroxyindoleacetic acid.[4]
- Inflammatory chronic diarrhea cause diarrhea with exudative, secretory, or malabsorptive components.
- Inflammatory causes of chronic diarrhea might present with features that suggest malabsorption or rectal bleeding.
- The nature of the malabsorption depends on the regions affected (e.g., proximal vs. distal small bowel), and rectal bleeding is usually a manifestation of colonic or rectal ulcerations.
- Anti-inflammatory agents, including bismuth subsalicylate or other more potent anti-inflammatory medications, appear to benefit patients with microscopic or collagenous colitis. [5]
- Motility disorders causing chronic diarrhea; both rapid transit time and a slow transit time can be associated with chronic diarrhea.
- Rapid transit time delivers fluid secreted during digestion to the distal small bowel or colon, this prevents re absorption of normally secreted fluid in the small bowel thereby overwhelming the re absorptive capacity of the colon.
- Reduced motility leading to slow transit might result in bacterial overgrowth with bile acid deconjugation, poor micelle formation, and steatorrhea.
- The clinical manifestations of chronic diarrhea caused by motility disorders include steatorrhea, usually up to 14 g per day.
- Osmotic laxatives results in acceleration of transit through the bowel, and this is associated with up to 14 g of fat in the stool.
- Presence of more than 14 g per day of fat in the stool might suggest the presence of bacterial overgrowth or associated disease such as celiac disease.[6]
- Iatrogenic causes of chronic diarrhea; After abdominal surgeries such as cholecystectomy about 5%–10% of patients develop chronic diarrhea.
- Most of these cases resolve completely or significantly improve within a couple of months.
- Iatrogenic diarrhea is related to excessive bile acids being delivered into the intestine.[7][8]
- After a cholecystectomy, bile is delivered directly into the small bowel, overcoming the terminal ileum's ability to reabsorb adequately leading to cholerheic diarrhea.
- Some other iatrogenic causes of chronic diarrhea might result from vagal injury and ileal resection.
For the genetics, associated conditions, gross pathology and microscopic pathology of some of the major causes of chronic diarrhea, please click below.
- Lactose intolerance
- Celiac sprue
- Chronic pancreatitis
- Lactase deficiency
- Lactulose
- Laxative use/abuse, and
- Whipple's disease
- Cholera
- Enterotoxigenic strains of E. coli
- Microsporidia
- Giardia
- Cryptosporidium
- Hyperthyroidism
References
- ↑ Sweetser S (2012). "Evaluating the patient with diarrhea: a case-based approach". Mayo Clin Proc. 87 (6): 596–602. doi:10.1016/j.mayocp.2012.02.015. PMC 3538472. PMID 22677080.
- ↑ Suarez FL, Savaiano DA, Levitt MD (1995). "A comparison of symptoms after the consumption of milk or lactose-hydrolyzed milk by people with self-reported severe lactose intolerance". N Engl J Med. 333 (1): 1–4. doi:10.1056/NEJM199507063330101. PMID 7776987.
- ↑ Morris AI, Turnberg LA (1979). "Surreptitious laxative abuse". Gastroenterology. 77 (4 Pt 1): 780–6. PMID 467934.
- ↑ von der Ohe MR, Camilleri M, Kvols LK, Thomforde GM (1993). "Motor dysfunction of the small bowel and colon in patients with the carcinoid syndrome and diarrhea". N Engl J Med. 329 (15): 1073–8. doi:10.1056/NEJM199310073291503. PMID 8371728.
- ↑ Pardi DS, Smyrk TC, Tremaine WJ, Sandborn WJ (2002). "Microscopic colitis: a review". Am J Gastroenterol. 97 (4): 794–802. doi:10.1111/j.1572-0241.2002.05595.x. PMID 12003412.
- ↑ Hammer HF, Santa Ana CA, Schiller LR, Fordtran JS (1989). "Studies of osmotic diarrhea induced in normal subjects by ingestion of polyethylene glycol and lactulose". J Clin Invest. 84 (4): 1056–62. doi:10.1172/JCI114267. PMC 329760. PMID 2794043.
- ↑ Breuer NF, Jaekel S, Dommes P, Goebell H (1986). "Fecal bile acid excretion pattern in cholecystectomized patients". Dig Dis Sci. 31 (9): 953–60. PMID 3731987.
- ↑ Arlow FL, Dekovich AA, Priest RJ, Beher WT (1987). "Bile acid-mediated postcholecystectomy diarrhea". Arch Intern Med. 147 (7): 1327–9. PMID 3606289.