week 4- stool Flashcards
• Indications for Stool Analysis:
o IBD, IBS o Chronic loose stools or constipation o Post-travel loose stools or diarrhea o Acute changes in bowel habits o Food intolerances o Bloating, maldigestion, malabsorption, excess gas o Chronic abd pain or discomfort o Poor eating patterns o Chronic fatigue o Anorexia o AI dz o Chronic skin conditions
• Stool sample collection:
o Specific instructions vary. In general:
o use clean container
o Avoid contamination w urine, menstrual blood, toilet water, TP (bismuth in TP & paper towels interferes w analysis)
o Collect before or 7 d after barium studies
o Collect before abx tx
o Avoid laxatives, including mineral oil
• Typical component of stool:
o Feces: 75% water, 25% solids
o 30% Bacteria: 1 gram has 10^9- 10^11 bacteria
o 10-20% Inorganic matter (Ca, PO4), 2-3% Protein
o 10-20% Fat: Primarily from bacteria & sloughed epithelial cells
o 30% Roughage: Indigestible dietary fiber, cellulose from previous 4 d), bile pigment, sloughed epithelial cells
o Intestinal secretions (mucus); WBCs from blood
• Stool Analysis Basics
o Amount o Transit time o Odors o Color o Mucus o Shape and consistency o Microscopic examination o Chemistry
• Transit times through GI areas:
o Mouth: 1 min o Esophagus: 4-8 sec o Stomach: 2-4 hrs o SI: 3-5 hrs o Colon: 10 hrs – several d
• Stool analysis, amount:
o ↓ fecal wt and ↓transit time are risk factors for colon CA
o Median daily stool wt =106g (UK)
o Globally, wt varies from 72 to 470g/day, inversely related to colon CA risk
o Significant relationship bw fecal wt and dietary fiber intake
o ↑fiber (18g/d) diets assoc w fecal wt 150g/d, ↓ risk colon CA
• Stool analysis, transit time (TT):
o Have patient ingest charcoal caps or whole corn kernels; note time: intake to output
o Varies from 12-48 hrs
o Healthy: TT mainly depends on total fiber & water intake
o Disease states: TT depends on fiber, mucosal factors, infectious & irritant agents
• Colonic Scintigraphy Sitzmarks Test:
o Measures TT
o Pros: Simple, reliable, inexpensive, reproducible
o Cons: requires good compliance of pt, exposure to radiation, doesn’t measure transit of physiologic meal
o take capsules each day for 3 d. X-rays on d 4 and 7. Count Amt of radio opaque rings.
o Total number = transit time.
o Rings: mb diff patterns
• Stool analysis, odor:
o usu odors dt bacterial conversion of protein to indole, skatole, mercaptans, H2S
o High meat diet usu = more odor
o Balanced bowel flora = more agreeable odor
o Foul: putrefaction of undigested protein, excessive fats oxidizing, Fermentation of excessive sugars
o Putrid: rancid or aromatic smell dt ulcerated & malignant tumors of bowel & large hemorrhages
o Sour and rancid: CHO fermentation & unabsorbed fatty acids
o Fetor hepaticus: sweetish foul odor dt liver failure: dimethyl sulfide & some ketones
o Cadavarine: body decomposition, CA, near death decarboxylation of lysine foul odor
• Stool analysis, color:
o Normal: light to dark brown, dt Stercobilin
o Yellow: milk diet, rhubarb, senna, fats, bilirubin, diarrhea, fast TT, bowel sterilization by abx
o Green: chlorophyll from green foods, biliverdin, diarrhea, calomel, indomethacin
o Clay: absence of stercobilin dt obstructive hepato-biliary dz, pancreatic dz, recent barium studies
o Red: lower GI bleed, red beets, tomatoes, tetracycline
o Blood streaked: hemorrhoids, rectal or anal dz
o Black or tarry: upper GI bleed ( > 100 ml), iron supplements, bismuth, charcoal, black jelly beans
o Dark red to chocolate brown: coffee, cocoa, chocolate, blackberries, cherries, red food coloring
o White: barium, antacids
o Orange: bx, pyridium (analgesic)
o other: drugs
• stool analysis, shpe & consistency:
o Normal: soft and formed (NOT fluid, mushy, or hard)
o Reflects shape and caliber (width) of colonic lumen
o colonic motility, colon wall abn
o Scybala: Small, round, dry, hard (constipation) “rabbit pellets”
o Soft and watery – D (secretory or osmotic); cathartics; protozoan, viral, bacterial infxn; D w pus and mucus: UC, Salmonella, Shigella; w blood: Typhoid, amebic dysentery, colon CA, Campylobacter; Mucus only: IBS, food allergies, colon CA
o Hard: constipation, dehydration, fever, excessive meat
o Gaseous: Soft and mushy w gas bubbles: excess CHO fermentation, celiac, ovarian CA
o Narrow, flattened, ribbon-like: spastic colon, colon CA (rectal narrowing), obstruction, stricture
o Greasy and Pasty: malabsorption fat - bile duct obstruction, pancreatitis, celiac , cystic fibrosis, pancreatic insuff
• Stool analysis, mucus:
o Normal: small amounts for lubrication, usu not visible
o ↑: Irritation, inflam, infx; Well mixed = from SI; Coating outside = LI
o Translucent gelatinous mucus on surface: Spastic constipation, Mucous colitis, Excessive straining at stool
o Bloody mucus clinging to feces: Neoplasm; Inflam rectal canal
o Villous adenoma of colon → passage of 3-4 L mucus in 24 hrs
o Mucus & D w WBC, RBC:UC, Bacillary dysentery (Shigella), amebiasis, Regional enteritis, ulcerating CA, acute diverticulitis
• Stool analysis, micro WBCs:
o Normal: (-)
o dt infx, inflam
o ↑, primarily Ns: chronic UC, bacillary dysentery, Localized abscesses, fistulas of rectum or anus, Shigella, Salmonella, Yersinia, invasive E-coli
o Mononuclear WBCs in typhoid
o Absence of WBCs: Cholera, viral D, amebic colitis, parasites
• Stool, micro, crystals, bacteria, yeast:
o Triple phosphate & calcium oxalate from foods
o Charcot-Leyden crystals: Rectangular orange, from disintegrated eosinophils, mb in parasite infx
o Bacteria: 1/3 dry weight; Normal 70% g(-), 30% g(+) (↑ w ↑CHO diet, intestinal ulcers, in infants dt milk diet)
o Yeast: Normal 0-5/hpf, > 5 suggests dysbiosis & intestinal candidiasis
• Stool chemistry: pH
o Normal: neutral to slightly alkaline, 7.0-7.5
o indicator of status of intestinal digestive processes
o > 7.5: ↓ TT/constipation, ↑protein, ↓ fiber (& ↓SCFAs); risk factor for colon CA (alkaline: ↓ SCFAs (especially n-butyrate), so colonic epithelial cells get less energy)
o lt 6.5: ↑TT/diarrhea, carb malabsorption
• fecal fat test, causes:
o =Gold standard to dx steatorrhea; 72-hr test requires standard daily diet: 100-150g fat, 100 g protein, 180g CHO x6 d before & during the collection period.
o 3 major causes of steatorrhea: Impaired intestinal fat absorption (Giardia), Deficiency of pancreatic digestive enzymes, Deficiency of bile
o Mb random stool or 72-hr collection (paint can)
o ↑Fat: Celiac, Crohn’s, Whipple, CF, chronic pancreatitis, pancreatic insufficiency
o > 6g/d is pathologic; > 20g/d in steatorrhea; Mod ↑ in diarrheal dz (may not necessarily indicate Malabsorption)
• Total fecal fast test:
o Sum of: Total TGs, cholesterol, PLs, LCFAs
o random sample measure mg of total fat/g stool, (+) correlation w 72 hr fecal fat
o ↓ levels not assoc w pathology
o Cholesterol: from dietary, bile, mucosal epithelial cell degradation; usu reabsorbed; ↑ = mucosal malabsorption (celiac); N: lt 0.3%, doesn’t vary w diet
o PL: from bile 50%, diet 25%, mucosal desquamation 25%; Phosphatidyl choline/serine/ethanolamine, cardiolipin; N=85% reabsorbed; ↑= Malabsorption, ↓ bile salt reabsorption, ↑mucosal cell turnover
o TG: most of fats (120g/d), usu abs in SI; ↑ mb def pancreatic enzymes, bile, stomach acid, ↑ fat diet, ↑ TT; if normal LCFA= pancreatic insufficiency; N: lt 0.3%
o LCFAs: Arachidonic acid (AA), Docosahexaenoic acid (DHA), Omega-3 polyunsaturated fatty acid; ↑= malabsorption, acute intestinal infection
o SCFAs
• Beneficial Short chain fatty acids:
o N: 56-156 umol/g; 44-72% Acetate, lt 32%proprionate, 10-33% n-butyrate
o dt fermentation of non-absorbed dietary fibers
o energy for colonocytes; trophic effect on intestinal lining; 5%-30% systemic daily energy requirements
o Deter colonization of pathogens in bowel (↓pH); Improve colonic blood flow
o Unbalanced ratios = “dysbiosis” or need ↑ dietary insoluble fiber
o ↑acetate/total SCFAs & ↓butyric/total found w large bowel adenomas and CA, compared to normal
o n-Butryate: main source energy for colonocytesl potent anti inflame, anti-CA effects, decreases intestinal permeability; ↓:IBD, colon CA; fiber fermented to butyrate (desirable); N: > 2.5 umol/g
o ↑SFCAs: Malabsoprtion, bacterial overgrowth, active colitis (but butyric acid enemas may heal UC)
• Putrefactive SCFAs:
o Valerate, isovalerate, isobutyrate
o ↑ dt bacterial fermentation of undigested protein
o N: 1.3-8.6 umol/g
o Hypochlorhydria, Pancreatic insufficiency, protein malabsorption, SIBO
• Stool chem, occult blood, normal or pathologic amounts
o Normal: (-), no detectable blood
o Upper GI bleed = black tarry stools = melena
o Consuming: black licorice, lead, iron pills, bismuth medicines (Pepto-Bismol), blueberries
o Lower GI bleed = overtly bloody stools = hematochezia
o Chemical detection required to find small amounts of blood in early GI dz
o Avg healthy person passes up to 2 mL daily
o > 2 mL in 24 hrs is pathologic
• Occult blood as screen:
o Screens: gastric ulcer, colon CA (+ while still in localized stages, proper tx 84% survival)
o Must do 3-6x on different samples, different days (intermittent bleeding)
o One-time sample detects only 24% of CAs
o Regular screening: at 50, key to prevent colon CA. USPSTF recommends for colon CA w high-sensitivity fecal occult blood, sigmoidoscopy/colonoscopy, 50-75
• Fecal occult blood test, guaiac method:
o Detects peroxidase in Hb
o blue = guaiac (+) result, presence of occult blood
o No/any color other than blue = (-), no blood in stool
o Certain foods, medications, and vitamin C can produce incorrect test results.
o False (+):has recently ingested red meat, raw vegetables or fruits, certain meds that irritate gastric mucosa, cause bleeding (aspirin, NSAID, anticoagulants)
o False (-): > 250mg/d up to 3 d before test, even if bleeding is present
• Immunoassay fecal occult blood stool test
o No dietary restrictions, only 1 stool sample
o ↑sens & spec over Guaiac method
o → right” patients to colonoscopy, earlier detection of polyps and colon CA
o Higher Patient Compliance
• Stool culture, normal:
o Stool has 450+ spp bacteria, but >90% NOT addressed by culture
o Freshly passed diarrhea stool is best specimen for enteric pathogens (at least 5 g feces)
o Collect before any abx tx
o Normal: 3+ to 4+ growth of good bacteria: inhibit pathogens, make vits (K, B), make butyric acid, prevent ↑beta-glucuronidase
o Normal flora: enterobacteriaceae (not common pathogens), bacteroides, strep, lactobacilli, pseudomonas, coagulase (-) staph, clostridium, peptostrep, bifidobacterium, eubacterium
• Stool culture, abn:
o Always include Blood or mucus, when present, pathogens often found
o Actual Pathogens: h pylori, salmonella, E coli, s aureus, campylobacter, v cholera, Yersinia enterocolitica, c difficile, shigella
o Potential pathogens: klebsiella, clostridium, citrobacter, candida
o ↓ normal flora: abx, ↓fiber
o Dysbiosis: ↓SCFAs, ↑yeast, IBS, food sens, leaky gut syndrome
o → IBD, arthritis, CT dz, skin dos
• Yeast culture and sens:
o Candida albicans, tropicalis; Rhodotorula, Geotrichum
o Normal: lt 2+ growth
o sensitivities if >/= 2+, both natural and pharm agents
• Dysbiosis index:
o = quick assess of GI health o calc based on culture, stool pH, SCFAs o Optimal: 0-3 o Slight Dysbiosis: >3-6 o Mod: lt 6-10 o Severe: >10
• Typical stool analyses ordered:
o MD: Occult blood, O&P, culture, fecal leukocytes, C diff toxin
o Functional Medicine practitioners: more info of CA risk, digestive fxn, intestinal inflam, etc; “panels” (Comprehensive Digestive Stool Analysis or GI Health Panel)
• Stool micro examination:
o Meat a vegetable fibers: reliable, (+) correlation w Heidelburg, etc, for maldigestion
o Meat fibers: normal is (-); Undigested fibers = impaired digestion: ↑consumption, improper chewing, ↑TT, Biliary obstruction, Hypochlorhydria, Pancreatic insufficiency (CF), Gastrocolic fistula
o Vegetable Fibers: normal 0-2; similar to meat; Often related to stressful eating or ↓ mastication
• Pancreatic insufficiency:
o Ssx: Post prandial bloating, pain, nausea; Loose greasy, foul smelling stools; Undigested food in stool; Malnutrition
o Affected enzymes: trypsin, chymotrypsin, elastase
• Trypsin:
o only made by pancreases; Susceptible to degradation by colonic bacteria
o N: 20-950 ug/g
o ↓: Pancreatic insufficiency, CF ( lt 20ug/g), Constipation: bacteria inactivate enzyme
o Interfering Factors: Bacterial proteases mb false (+); Barium and laxatives within 1 wk; Constipation
o Chymotrypsin is a better test of pancreatic fxn
• Chymotrypsin:
o Fecal levels reflect Pancreatic proteolytic enzyme activity
o ↓: Pancreatic insufficiency, hypochlorhydria, CF
o ↑: ↑TT, rarely dt ↑ chymotrypsin output from pancreas
o N: 6.2-41 U/g
o Supplementation affects lab values
• Elastase:
o Proteolytic, only made by pancreas
o Accurately reflects exocrine pancreatic fxn
o Strong correlation w gold standard test for pancreatic insuf (secretin-caerulein test), sens 90%, spec 93%
o ↓: 50% DM1, 35% DM2, 33% osteoporosis, > 35 (pancreatic fxn ↓ w age), Gallstone formers or post cholecystectomy
o Useful to monitor: CF, Chronic pancreatitis, AI & CT dz, chronic IBD
o N: 200 ug/g
o Mild panc insuf: 100-200
o Severe: lt 100
• Elastase vs chymotrypsin:
o Correlate w secretin pancreozymin test: yes; no
o Affected by TT: no; yes
o Enzymatically degraded in gut: no; yes
o Affected by digestive enzyme supplementation: no; yes
• Bile:
o Fxns: Improve fat digestion and absorption, Enhance excretion of endogenous wastes like bilirubin and cholesterol
o Secreted by liver/gall bladder (600-1000 mL/dL per d) and transformed by colonic bacteria into secondary bile salts
o Only secondary bile salts are secreted in stool: Lithocholic acid (LCA) and deoxycholic acid (DCA)
o 2nd bile salts ↑ in diet ↑animal fat/protein, ↓fiber → 2-5x ↑ excretion LCA/DCA
o LCA more toxic than DCA: inhibits enzyme glutathione-S-transferase (powerful antioxidant)
o LCA/DCA ratio > 1: correlated to ↑risk of colon CA, gallstones, cholecystectomy, breast CA
o Lactobacillus can bind LCA and DCA, ↓their bioavailability
o Fiber in diet and probiotics can ↓ LCA/DCA ratio
• CDSA- metabolic markers:
o Beta-Glucuronidase: de-conjugates glucuronides, inhibit fecal excretion of steroid hormones (estrogen), drugs, toxins (carbamate pesticides, aniline dyes).
o Produced by various bacteria: E. coli, Bacteroides, Clostridium.
o ↑: mb → colon CA, estrogen-related CA dt ↑ enterohepatic re-circulation of de-conjugated estrogen
o N: lt 300 U/g
o Inflammatory markers: sIgA, fecal lysozyme, calprotectin, alpha anti-chymotrypsin, eosinophil protein X (EPX), lactoferin
• Total intestinal secretory IgA (sIgA)
o sIgA normally ↑ in GI mucus, ~ 3 g/d
o ↓ uptake food Ags, bacterial toxins, macromolecules
o ↓: food allergies/sens, chronic parasitic infx, malabsorption, villous atrophy
o ↑: up regulated immune system
o Fecal: good idea of intestinal production, ~90% accurate
• Intestinal lysozyme:
o made by Paneth cells in Crypts of Lieberkuhn
o part of intestinal anti-microbial & anti-inflam defense (bacterial protease and natural anti-histamine)
o differentiate IBD (↑) from IBS (N)
o w alpha a-chymotrypsin to differentiate inflam in SI vs. both S/LI
o ↑: Crohn’s, UC (also proctitis), infx & non-infx enteritis, col on CA,
o ↓: disease remission
• Alpha anti-chymotrypsin (ACHY)
o made by liver, lungs, kidneys, endothelium, intestinal epithelium (esp SI)
o serine protease inhibitor
o Inhibit protease enzymes from tissues after damage (anti-inflam) (↑ 5x w/in 8 hrs)
o ↓ACHY → ↑tissue destruction in area affected: GI inflame
o A little more specific for crohn’s b/c of SI involvement
o ↑↑ (>180): inflam total LI, mb SI too
o also ↑ intestinal lysozyme = total LI/SI
o N lys but ↑↑ ACHY = SI only
o Mild/mod ↑(100-180): only distal colon
• Calprotectin, uses:
o secreted by neutrophils
o Sens, non-invasive marker for colon CA, bowel inflam
o differentiate IBD (+) from IBS (-, also lower ESR and CRP)
o ↑ in >95% pts w IBD, correlates w dz activity: monitor tx, define remission, predict relapse early, identify pts for endoscopy/colonoscopy
o ↑: crohn’s, UC, neo?
o ↓: IBS, HS?
• Calprotectin, levels:
o Lt 50 ug/g= No sig inflam
o 50-100 = Some GI inflam: IBD, infx, polyps, neoplasia, NSAIDS
o >100 = Sig inflam: mb refer for imaging, bx, etc
o >250= Active dz; predicts imminent relapse
• Lactoferrin:
o = iron binding protein in neutrophil granules. ddx inflam vs non-inflam conds
o ↑: mucosal inflam dt bacterial infx, parasitic, diverticulitis, IBD
o Interfering Factor: mb found in stool of breastfeeding infants
o Normal: (-)
• Eosinophil Protein X
o Released from eosinophils: Food allergies, parasites, celiac
o reflects E response, IgE inflam, tissue damage
o More sensitive than lactoferrin for low level inflam
o Less intra-individual variability
o ↑: IBD, colon CA, parasites, allergies, atopic derm
