faecal analysis

7/29/2019 Faecal Analysis

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FAECAL ANALYSISJoseph T. Sabido


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What's faecal

Analysis???Or Analysis of Faecal matter, just to be formal...

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are needed to see this picture.

*


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*Necessary evil*




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Faecesend product

of bodymetabolism

provide

valuablediagnosticinformation


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Routine Faecal Examination(macroscopic, microscopic &

chemical analysis)

for early detection of the ff:

gastrointestinal bleeding

liver and biliary duct disorders

maldigestion/ malabsorption syndrome

inflammation

causes of diarrhoea and steatorrhea


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Physiology


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Normal Faecal

Specimen contains:bacteria

cellulose

undigested foodstuffs

gastrointestinal secretions

bile pigments

cells from the intestinal walls

electrolytes

water


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*FlatusIntestinal gas


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Carbohydrates

resistant to digestion pass through theupper intestine

metabolised by bacteria in lower intestine

producing large amount of flatus


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Alimentary tracttubular passage ofmucous membrane

and muscleextending about8.3 meters frommouth to anus;

functions indigestion andelimination.


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Small IntestineThe narrow,winding, upper partof the intestinewhere digestion iscompleted andnutrients areabsorbed by theblood. It extendsfrom the pylorus to

the caecum andconsists of theduodenum, thejejunum, and theileum.


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Digestive Enzymestrypsin

chymotrypsin

amino peptidase

lipase

Bile salts

Aid in the digestion of fatty acids


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Fluid within the ATingested fluid 2000 mL

saliva - 1500 mL

gastric 1500 mL

liver 1000 mL

pancreatic 1000 mLintestinal secretions 2000 mL

(water and electrolytes)


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Under Normal Conditions

500 to 1500 mL reaches the largeintestine

150 mL excreted in the faeces

Water and Electrolytes

absorbed in both the small and large

intestine* faecal electrolyte content is similarto that of plasma


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Large intestineThe large intestine is theportion of the digestive systemmost responsible for absorptionof water from the indigestibleresidue of food. The ileocaecalvalve of the ileum (smallintestine) passes material intothe large intestine at thecaecum. Material passesthrough the ascending,

transverse, descending andsigmoid portions of the colon,and finally into the rectum.From the rectum, the waste isexpelled from the body.


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Large IntestineIt is capable of absorbing an approximate volumeof 3000 mL of water.

If the amount of water reaching the large intestineexceeds the normal volume (9000 mL,) it isexcreted with the solid faecal material, producingdiarrhoea

Constipation:

Provides time for additional water to bereabsorbed from the faecal material, producingsmall, hard stools.


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DisordersDisorders often associated with the Alimentary tract


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DiarrhoeaIncrease in daily stool weight (above 200 g) with increased liquidity and frequency of more than 3

times a day.


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Four Factors in diarrhoeaclassification

Duration of the illness

Mechanism

Severity

Stool characteristics


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Acute diarrhoea (less than 4

weeks)Chronic diarrhoea (more than 4weeks)


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A. Secretory Diarrhoea

Bacterial and protozoan infectionsproduce increased secretion of waterand electrolytes which override the

reabsorptive ability of the largeintestine.

Major Mechanisms of

Diarrhoea


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Causes

Enterotoxin-producing

organismsOther causes

- Escherichia coli- Clostridium spp- Vibrio cholera- Salmonella spp- Shigella spp- Staphylococcus spp

- Campylobacterprotozoa- Cryptosporidium

- Drugs- Stimulant laxatives- Hormones- Inflammatory bowel

disease- Endocrine disorders

- Neoplasms- Collagen vasculardisease


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B. Osmotic Diarrhoea

Incomplete breakdown orreabsorption of food presents anincreased faecal material to thelarge intestine

Retention of water andelectrolytes in the large intestine


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Causes:

Disaccharidase deficiency (lactoseintolerance)

Malabsorption (celiac sprue)

Poorly absorbed sugars (lactose, sorbitol,mannitol)

Laxatives

Magnesium - contains antacids

Amoebiasis

Antibiotic administration


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C. Altered Motility

Conditions of enhanced motility

(hypermotility) or slow motility(constipation)

Can be caused by Irritable bowel

Syndrome


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Irritable Bowel syndrome

A functional disorder in whichthe nerves and muscles of thebowel are extra sensitive

Causes cramping, bloating,flatus, diarrhoea, constipation

Triggered by certain food,chemicals, emotional stress andexercise


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Rapid Gastric Emptying Dumping

Syndrome

Describes hypermotility of thestomach and the shortenedgastric emptying half-time, whichcauses the small intestine to filltoo quickly with undigested food.

Hallmark for Early DumpingSyndrome


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Normal Gastric Emptying Half-Time(around 35-100 minutes)

Controlled by:Fundic tone

Duodenal feedback

Gastrointestinal Hormones


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Rapid Gastric Emptying

Gastric emptying time of lessthan 35 minutes.

Caused by disturbances in thegastric reservoir or in thetransporting function

Divided into two: Early dumpingsyndrome and Late Dumping


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Dumping Syndrome

Hypoglycemia is often a complication

Causes of DS:

Gastrectomy

Gastric bypass surgery

Post-vagotomy status

Bollinger-Ellison syndrome duodenalulcer disease

Diabetes melitus


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COMMON TESTS FOR DIARRHOEA

Secretory Osmotic

Stool Cultures Microscopic Faecal Fats

Ova and Parasiteexaminations

Muscle Fibre Detection

Rotavirus Immunoassay Qualitative Faecal Fats

Faecal Leukocytes

Trypsin ScreeningQuantitative Faecal Fats

ClinitestD-Xylose tolerance test

Lactose tolerance testFaecal Electrolytes

Stool pHFaecal Osmolality


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Malabsorption

Abnormal nutrient absorption or digestionof fats, meat fibres and carbohydrates

Often leads to malnutrition and anaemia

Urine D-Xylose is low.


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Maldigestion

Impaired digestion due to lack of digestiveenzymes


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Colorectal Cancer

Causes increased blood loss in theGastrointestinal Tract

Detected via Occult Blood Testing


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Cystic Fibrosis

Disease of Accessory organ

Hereditary disease that affects mucoussecretion in the pancreas and lungs

Decreased pancreatic enzymes(trypsin/chymotrypsin/elastase)


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Steatorrhoea

Detection of Steatorrhea:

For the diagnosis of pancreatic insufficiency and

small bowel disorders

Pancreatic disorders that increase the productionof pancreatic enzymes:

Cystic FibrosisChronic Pancreatitis

Carcinoma


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Present maldigestion andmalabsorption conditions

Distinguished by the D-Xylosetest (Normal D-Xylose Testindicates pancreatitis)


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The Proper How-Tos in Collecting Faecal Specimen

Specimen Collection


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Collect the specimen in a cleancontainer (e.g. Bed pan or disposable

container) then transfer to thelaboratory container

Wide-mouth, chemically clean, and

sterile bottles

Kits for the collection of specimens to bescreened for occult blood paper can be

floated in the toilet bowl to collect thespecimen (only to be used whencollecting specimen using the kit inwhich they are included)


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Containers with preservatives for ova andparasites (must not be used for other tests)

Interferences:

Urine contamination: destroys protozoa instool

Water contamination: interferes with labtesting

Failure to adhere to diet recommendation:affects the faecal specimen

Enemas and Barium Sulphate: affects stoolsamples for microscopy (fat, fibres,parasites)


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LaboratoryExaminations


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Microscopic

Examination

Size, shape, consistency, color

Presence or blood, mucous, pus, tissue,food residues or parasites


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Appearance Usual CausesSmall, hard dark balls Constipation

Voluminous, odorous,floating

Malabsorption of fats orprotein

Loose, contains mucus,

but no blood

Irritable bowelsyndrome, diffuse

superficial inflammation,Villous adenoma

Loose, contains mucus

and blood

Inflammatory bowelsyndromes, Typhoid,

shigellae, amoebae,carcinoma

Sticky, black, tarryUpper GI tracthaemorrhage


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Appearance Usual Causes

Voluminous, watery, littleformed material

Non-invasive infections(cholera, toxigenic, E. coli,

staphylococcal foodpoisoning)

Osmotic Catharsis

(disaccharidase deficiency,binge-type overeating)

Loose, contains pus and or

necrotic tissue

Diverticulitis or otherabscesses

Necrotic tumorParasites

Pasty, grayish-white, littleodour

Bile duct obstructionBarium Ingestion


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The Colours of Faeces


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ColourNon-

pathologicPathologic

Brown, darkbrown, yellow-

brown

Normal oxidationof bile pigments

None

Very dark brownProlonged

exposure to air,diet high in meat

None

BlackIron, Bismuth

ingestionBleeding from GI

tract

GreyChocolate, cocoa

ingestion

Steatorrhoea(consistency usually

mushy/frothy)


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ColourNon-

pathologicPathologic

Very light greyDiet high in milkproducts, Barium

ingestion

Bile ductobstruction

Green/ Yellow-green

Diet high inSpinach, other

greens

Rapid transittime, preventingoxidation of bile

pigments

RedLaxatives,

vegetable origin,diet high in beets

Bleeding from GItract


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MicroscopicExamination

Its the same world, only a thousand times smaller


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Performed to detect the presenceof Leukocytes associated with

microbial diarrhoea andundigested fibres and fatsassociated with steatorrhoea


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Faecal Leukocytes (neutrophils): Dysentry

Eosinophils: Amoebic infections

Large amounts of epithelial cells/large

amount of mucous: irritated mucosa

Abnormal findings


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Faecal Leukocytes

Seen in conditions that affect the IntestinalMucosa

Microscopic screening is performed as apreliminary test to determine whetherdiarrhoea is being caused by invasivebacterial pathogens

Diarrhoea caused by Staphylococcusaureus and Vibrio spp. Do not cause theappearance of faecal neutrophils


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Specimen staining and Staining reagents used:

Specimens can be examined as wetpreparations stained with Methylene blue(faster procedure but difficult to interpret) oras dried smears with Wrights or Gram Stain

(provide permanent slides for evaluation.All slide preparations must be performedwith fresh specimens

A lactoferrin latex agglutination test isavailable for the detection of fecalleukocytes and remains sensitive onrefrigerated and frozen specimens


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Interpretation:

Indicative of invasive bacteria:

Under high power objective, asfew as three neutrophils

Using oil immersion, finding of anyneutrophil has approximately 70%sensitivity.

Presence of Lactoferrin latexagglutination


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Presence of striatedmuscle fibres are seen

in patients withmaldigestion (cysticfibrosis andhypermotility,)pancreaticinsufficiency, in biliaryobstruction andgastrocolic fistulas

Muscle Fibres


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Procedure:

Patients should be instructed to include red meatin their diet prior to the collection of specimen

Specimens should be examined not later than 24hours after collection

Emulsify a small amount of stool in 2 drops of10% alcoholic eosin, which enhances musclefibre striations

Coverslip then let stand for 3 minutes

The entire slide should be examined within 5minutes in high power objective

Count the number of undigested fibers.


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Appearance of the fibers

Undigested fibers: visible striationsrunning both vertically andhorizontally

Partially digested fibers: striations inonly one direction

Digested fibers: no visible striations

Manner of reporting:

Increased: >10 fibers/hpf =creatorrhoea


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Qualitative Faecal Fat

Testing


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Steatorrhoea

Increased fecal fat

Present in conditions that decreasepancreatic enzymes and in malabsorption.

Pale and greasy looking stool with foulodour.

Mineral oils and creams cause falsepositive.


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Qualitative Tests

Used to monitor patients undergoingtreatment for malabsorption disorders.

Sudan III is routinely used for staining.

Two parts: Neutral fat stain and Split fatstain


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Stains: Sudan III, Sudan IV and Oil Red O

TAG (neutral fats)

Sudan III in 95% Ethanol

Normal:


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Cholesterol

Cholesterol is stained with Sudan

III after heating and as thespecimen cools, it forms crystalsthat can be identified

microscopicallySoap and fatty acids do not staindirectly with Sudan III, therefore,

a second slidemust be examinedafter the specimen has beenmixed with acetic acid andheated.


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Intestinal malabsorption: normalneutral fats, increased soap andfatty acids

Maldigestion leading tosteatorrhoea: increased neutral

fats


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Chemical Testing for

Faeces


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Blood in faecesBleeding in the upper GI tract mayproduce black, tarry stool, and bleeding inthe lower GI tract may result in overly

bloody stool.

Any bleeding in excess of 2.5mL/150g ofstool os considered pathologic

Melena: a very large amount of faecalblood

Appears a black, tarry stool


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Colonic bleeding causes red or

maroon stoolsStreaks of bright red blood on thestool surface denotes:

Haemorrhoidal bleeding

Ulcerative colitis

Friable adenomas

Superficially eroded carcinomas


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Faecal Occult Blood Testing (FOBT) isused as a mass screening procedure for theearly detection of colorectal cancer.

It is the most frequently encounteredscreening test for occult blood and is basedon the detection of pseudoperoxidase

activity of haemoglobin. This is the sameprinciple as that of the reagent strip test forurinary blood, but uses a different indicatorchromogen.

Tests for Blood

G i T ti


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Guiac Testing

Most common

Utilises a Guiac-impregnated paper incardboard holder

Blue colouration indicates presence of

either Haemoglobin, peroxidase orpseudoperoxidase

Less sensitive

Others:

Benzidine, Orthotoluidine, andimmunological tests (more susceptible tofalse positive results)


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Quantitative Faecal

Fat Testing


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Used as confirmatory test for

steatorrhoeaRequires a collection of a 3-dayspecimen

Patient must be maintain aregulated intake of fat (100g/day)prior to and during the collection

Paint can can make an excellentcollection container.

d


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Routinely used and is the Gold standard

Faecal lipids are converted to fatty acids andtitrated to neutral endpoint with sodium hydroxide

Fat content is reported as grams of fat or thecoefficient of fat retention per 24 hours

Normal values are based on 100g/day

Van de Kamer

Titration


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Acid Steatocrit

Rapid test to estimate the amount of fat

excretion, having a 72-hour stoolcollection

Reliable tool to monitor a patients

response to therapy and screen forsteatorrhoea in paediatric populations

Near-Infrared


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Near InfraredReflectance

SpectroscopyA rapid procedure that requires less stool.

Requires 48 to 72 hour stool collection

Result is based on the measurement andcomputed processing of signal data from

reflectance of faecal surface, which isscanned with infrared light between1400nm and 2600nm


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Foetal Haemoglobin


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Blood in vormitus or stool

Source must be differentiated if eitheringested from the mother (maternalHbA), or from own GIT (foetal HbF)

Avoid black or tarry specimenApt Test

(vomitus/stool + H2O) + dilute NaOH

HbF - no change in colour (pink)

HbA - yellow or brown


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Faecal Enzymes


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Gelatin test is done, which is an

insensitive procedure that detects onlysever cases of pancreatic insufficiency

When present in stool, it digests thegelatin on the paper, inability to digest

indicates a deficiency in trypsinproduction

Trypsin


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Chymotrypsin

More resistant to intestinal degradation

and a more sensitive indicator of lesssever cases

Capable of gelatin hydrolysis but is most

frequently measured byspectrophotometric methods


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Elastase 1

Strongly resistant to degradation

Accounts for about 6% of all secreted

pancreatic enzymes

Can be measured by immunoassay using ELISAkit.

Provides a sensitive indicator of exocrinepancreatic insufficiency

Uses a single stool sample.


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Faecal Carbohydrates


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Osmotically active

Triggers movement of large amounts of H2O to intestines

CHO in stool = fluids and electrolytes = diarrhoea

Seen in

Celiac disease (impaired CHO reabsorption)

Ph 7-8 normal pH5.5Lactose intolerance ( sugar digesting enzymes)

Congenital disaccharide deficiencies

Disaccharides

T t f


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Tests for

Carbohydrates

Faecal Carbohydrate Testing (faecal

diarrhoea assessment and inflammatorynecrotising enterocolitis)

Copper reduction test

Ph paper


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D-Xylose TestUseful screening test for carbohydratemalabsorption

If given orally, the amount excreted in a urine

sample collected five hours after administrationcan be measured

>3g D-Xylose in Urine: Normal


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