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38 Cards in this Set
- Front
- Back
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constipation definition |
infrequent/difficult evacuation of stool; <2 bowel mvmts/wk |
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defecation coordination |
relaxation & contraction of pelvic floor muscles & anal sphincters |
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secondary causes of constipation |
diet/lifestyle, structural, neuro, endocrine, metabolic, myopathic, psych, meds (opiates, Ca antagonists) |
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idiopathic constipation |
MCC constipation; 2 main mechanisms = slow transit constipation & pelvic floor dysfunction |
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slow transit constipation |
common; poor propulsion secondary to neuromuscular dysfunction, methane |
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pelvic floor dysfunction |
rectum fails to expel feces; anal canal fails to open effectively; dyschezia (difficult evacuation) + dyssynergia (contraction of pelvic floor/ext. anal sphincter during defecation) |
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functional studies - severe chronic constipation |
colon transit study, anorectal manometry (measure sphincter P, responses to distention) |
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Rx of constipation |
diet/lifestyle, laxatives, biofeedback & habit training, chloride secretagogues, systemic agents, surgery |
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Chloride secretagogues |
Lubiprostone = direct action on apical Cl- channels Linaclotide = indirect action on Cl- channels |
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diet & lifestyle changes |
20-30g of fiber/d increases stool frequency and weight, may worsen bloating & distention |
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types of laxatives |
bulk (agar fibers, methyl cellulose, bran), osmotic laxative (MgOH, lactulose), stimulants/irritant (castor oil), stool softener |
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biofeedback & habit training |
teach proper defecation technique, routine - induce w/ suppositories or enema; helpful in pelvic floor dysfunction patients |
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systemic agents for constipation |
Prucalopride - promote peristalsis, decr. visceral pain; Methylnaltrexone - peripheral u receptor antagonist (opiate-induced constipation only) |
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diarrhea definition |
incr. frequency of watery stools >3 times/d |
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diarrhea pathophysiology |
10L fluid enters jejunum, 90% absorbed; 1000 mL enters colon each day, 90% absorbed; 80-100 mL excreted in feces; if more water passes or less water is absorbed = diarrhea |
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osmotic diarrhea |
ingestion of poorly absorbed substances => retain more water in stool; electrolyte absorption unaffected |
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Fecal osmotic gap |
estimating concentration of osmotically active substances in diarrheal patients; 290 mosm/kg - 2(Na+K) |
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fecal osmotic gap >125 mosm/kg |
diagnostic of osmotic diarrhea |
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fecal osmotic gap <50 mosm/kg |
secretory diarrhea |
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types of diarrhea |
osmotic, secretory, inflammatory, fatty |
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osmotic diarrhea causes |
ingestion of poorly absorbed carbs, sugar alcohols, ions |
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secretory diarrhea causes |
congenital chloridorrhea (rare), bacterial infections, inflammatory (microscopic colitis), dysregulation, reduction of SA, endocrine (VIP-oma) |
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congenital causes of secretory diarrhea |
absence of ion transport mechanism - chloridorrhea = loss of Cl-HCO3 exchanger so can't remove Cl against concentration gradient; Rx = decr. Cl load to intestines by decr. gastric HCl secretion (omiprazole) |
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infective causes of secretory diarrhea |
secretion of enterotoxins, invasion of mucosa, production of cytotoxins, bacterial adhesion to enterocytes |
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E. colo - secretory diarrhea |
EIEC (shigella-like toxin) increases Cl secretion; EHEC O157:H7 is Shiga-like toxin, non-invasive |
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Cholera toxin - secretory diarrhea |
toxin internalized, activates G protein of adenylate cyclase -> cAMP -> inhibit Na absorption + stimulate Cl secretion |
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microscopic colitis = infl. cause of secretory diarrhea |
watery diarrhea & dehydration; endoscopically looks normal, see lymphocytic infiltrate & subepithelial collagen thickening under microsocpe; Rx underlying cause (anti-diarrheals, budesonide) |
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Dysregulation/dysmotility & secretory diarrhea |
IBS, diabetic autonomic neuropathy, post-vagotomy diarrhea, postsympathectomy diarrhea = abn ENS fxn changes GI motility & electrolyte absorption |
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endocrine causes = secretory diarrhea |
rare; endocrine cells in gut, pancreas produce hormones -> inhibit absorption or cause secretion ex = VIP-oma, somatostatinoma, mastocytosis, medullary CA of thyroid |
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acute (<4 weeks) diarrhea cause |
infective etiology more likely; see lymphocytosis (viral), neutrophilia (bacterial), neutropenia (salmonellosis), incr. BUN & Cr; stool tests = fecal calprotectin, wbc's |
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eval of chronic diarrhea |
stool analysis & osmotic gap, pH of stool water (low = carbohydrate malabsorption), steatorrhea (maldigestion/absorption) |
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common causes of chronic watery diarrhea - osmotic diarrhea |
Magnesium-induced diarrhea (Mg in stool >90 meq/L) and carbohydrate malabsorption |
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organisms that cause >4 weeks watery diarrhea (secretory) |
Aeromonas, Pleisomonas, Giardia, coccidia, Cryptosporidiosis, Microsporidia |
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important causes of chronic infl. diarrhea |
infective (C. difficile, CMV, amebiasis, TB), IBD, ischemic colitis, radiation colitis, malignancy |
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chronic fatty diarrhea evaluation |
steatorrhea - >14g fat in stool/24h suggestive of fat malabsorption; causes = mucosal dz (Celiac), pancreatic exocrine insufficiency, cholestasis (advanced liver dz, biliary obstruction) |
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Rx diarrhea |
rehydrate, correct electrolyte abn - oral rehydration therapy (ORT) or IV fluids |
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non-specific antidiarrheals |
opiates (loperamide, diphenoxylate w/ atropine), intraluminal agents (Bismuth), adsorbents (Kaolin) |
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empirical rx of chronic diarrhea |
opiates, octreotide (somatostatin analog), clonidine (adrenergic agonist), Psyllium |
