week 4- stool Flashcards
(43 cards)
• 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
