Fecal - PowerPoint Presentation

Slide1

Fecal Chemical Tests

Medical Parasitology Lab.

Fecal Fat Testing & Reducing Sugars

Raed Z. Ahmed, Medical Parasitology Lab.,2012-2013

Prepared By:

Mr. Raed Z. AhmedSlide2

Diarrhea Diarrhea

is defined as an increase in daily stool weight above 200 with increased liquidity and frequency of more than three times per day.Diarrhea classification can be based on four factors: duration of the illness, mechanism, severity

, and stool characteristics.Diarrhea lasting less than 4 weeks is defined as acute

, and diarrhea persisting for more than 4 weeks is termed

chronic

diarrhea.

The major mechanisms of diarrhea are secretory, osmotic, and altered motility.The laboratory tests used to differentiate these mechanisms are fecal electrolytes (fecal sodium, fecal potassium), fecal osmolality, and stool pH.

Raed Z. Ahmed, Medical Parasitology Lab.,2012-2013Slide3

Continue…….Secretory Diarrhea:

Bacterial, viral, and protozoan infections produce increased secretion of water and electrolytes, which override the reabsorptive ability of the large intestineOsmotic Diarrhea: Incomplete breakdown or reabsorption of food presents increased fecal material to the large intestine, resulting in the retention of water and electrolytes in the large intestine which in turn results in excessive watery stool.Altered Motility: Altered motility describes conditions of enhanced motility (hypermotility) or slow motility (

constipation).Raed Z. Ahmed, Medical Parasitology Lab.,2012-2013Slide4

Malabsorption & Maldigestion

Malabsorption is defined as the impaired absorption of nutrients by the intestine.Maldigestion is defined as the

impaired digestion of food.Maldigestion and malabsorption contribute to osmatic diarrhea.

Specific nutrient absorptive disorders:Carbohydrate Malabsorption

Fat malabsorption/Maldigestion

Protein Malabsorption

Mineral and Vitamin Malabsorption Raed Z. Ahmed, Medical Parasitology Lab.,2012-2013Slide5

Investigations of Malabsorption

Investigations of Carbohydrate Malabsorption:D- xylose TestLactose IntoleranceStool Reducing Sugar Investigations of

Fat Malabsorption:Fecal Fat TestInvestigations of Protein Malabsorption:

Albumin Level

α

1

- antitrypsinInvestigations of Mineral and Vitamins Malabsorption:Stool Electrolyte (Na+, K+)

Raed Z. Ahmed, Medical Parasitology Lab.,2012-2013Slide6

Investigation of Carbohydrate Malabsorption

Stool Reducing SugarThis test measures unabsorbed sugars in stool. It is used to evaluate the body's ability to digest carbohydrates, or to absorb nutrients from food and drinks.Testing for fecal reducing substances detects congenital disaccharidase deficiencies as well as enzyme deficiencies due to nonspecific mucosal injury.Fecal carbohydrate testing is most valuable in assessing cases of infant diarrhea and may be accompanied by a pH determination.

The copper reduction test is performed using a Clinitest tablet and one part stool emulsified in two parts water .

Raed Z. Ahmed, Medical Parasitology Lab.,2012-2013Slide7

A result of 0.5 g/dL is considered indicative of carbohydrate intolerance.The

Clinitest on stools can distinguish between diarrhea caused by abnormal excretion of reducing sugars and those caused by various viruses and parasites.

Sucrose is not detected by the Clinitest method because it is not a

reducing sugar

.

A

positive result would be followed by more specific serum carbohydrate tolerance tests, the most common being the D-xylose test for malabsorption and the lactose tolerance test for

maldigestion.

Continue …….

Raed Z. Ahmed, Medical Parasitology Lab.,2012-2013Slide8

The Fecal Reducing Substances test is performed in a laboratory, on a sample of stool as small as 5 grams.Unfortunately

this sample needs to be delivered to the laboratory ASAP, preferably within 1 hour. This is because lactose (or other sugars) in the stool will normally be broken down by chemical processes within 2-4 hours after

the specimen is producedAdults and Children :

Normal: = 0.25

g/dl

Suspicious: 0.25-0.5

g/dl Abnormal: > 0.5 g/dl Continue …….

Raed Z. Ahmed, Medical Parasitology Lab.,2012-2013Slide9

Investigation of Fat Malabsorption

Steatorrhea: is the presence of excess fat in feces, Stools may also float due to excess lipid, have an oily appearance and be especially foul-smelling.

There is increased fat excretion, which can be measured by determining the fecal fat level.Possible biological causes can be lack of bile

acids, defects in pancreatic

enzymes “

maldigestion

”, and defective mucosal cells “malabsorption”.The absence of bile acids will cause the feces to turn gray or pale.Quantitative fecal fat analysis is used as a confirmatory test for steatorrhea

Raed Z. Ahmed, Medical Parasitology Lab.,2012-2013Slide10

Fecal Fat TestFecal fat testing can be done by either qualitative microscopy method or quantitative methods.Qualitative Microscopy Method

:Is the simplest form of the fecal fat test, a random fecal specimen is submitted to the hospital laboratory and examined under a microscope after staining with a Sudan III dye. Visible amounts of fat indicate some degree of fat malabsorption.The staining procedure consists of two parts,

the neutral fat stain and the split fat stain.

Investigation of Fat Malabsorption

Raed Z. Ahmed, Medical Parasitology Lab.,2012-2013Slide11

Qualitative Microscopy Fat Testing

Neutral fats stain are readily stained by Sudan III and appear as large orange-red droplets, often located near the edge of the coverslip.

Observation of more than 60 large orange-red droplets/HPF can be indicative of steatorrhea.The split fat

stain

representing total fat content can provide a

better indication.

The breakdown of neutral fats by bacterial lipase and the spontaneous hydrolysis of neutral fats may lower the neutral fat count. Observation of more than 100 large orange-red droplets/HPF can be indicative of steatorrheaThis

also precludes the comparison of

the two

slide tests to determine whether maldigestion or

malabsorption is

causing steatorrhea

Raed Z. Ahmed, Medical Parasitology Lab.,2012-2013Slide12

Neutral Fat Stain Procedure

Homogenize one part stool with two parts water.Mix emulsified stool with one drop 95% ethyl alcohol on slide.Add two drops saturated Sudan III in 95% ethanol.

Mix and coverslip. Examine under high power

Count orange droplets per high-power field

Split Fat Stain Procedure

Mix emulsified stool with one drop of 36%

acetic acid.Add two drops saturated Sudan III.Mix and

coverslip.

Heat gently almost to

boiling.

Examine under high

power.

Count and measure the orange droplets per

high-power field

Procedures

Raed Z. Ahmed, Medical Parasitology Lab.,2012-2013Slide13

Quantitative Fat Testing

Quantitative fecal fat analysis is used as a confirmatory test for steatorrhea.Quantitative fecal analysis requires the collection of at least a 3-day specimen.

The patient must also maintain a regulated intake of fat (100 g/dl)

prior to and

during the collection

period.

Refrigerating the specimen prevents any bacterial degradation.The method routinely used for fecal fat measurement is the Van de Kamer titration, although gravimetric methods are available.

Fecal lipids are converted to fatty acids

and

titrated to a neutral endpoint with sodium

hydroxide.

Raed Z. Ahmed, Medical Parasitology Lab.,2012-2013Slide14

Continue …….The fat content is reported as grams of fat or the coefficient of fat retention per 24 hours.

The coefficient of fat = Normal values based on a 100 g/dl intake are 1 to 6 g/dl or a coefficient of fat retention of at least 95%.

Although the Van de Kamer titration is the gold standard for fecal fat, the acid Steatocrit is a rapid test to estimate the amount of fat

excretion.

It is similar to the microhematocrit

test.

( dietary Fat – Fecal Fat )

dietary Fat

X 100

Raed Z. Ahmed, Medical Parasitology Lab.,2012-2013Slide15

The acid steatocrit is a reliable tool to monitor a patient’s response to therapy and screen for steatorrhea in pediatric populations.Acid

steatocrit % =An acid steatocrit value less than 31% was considered normal while a value greater than 31% indicated steatorrhea in adults.Acid steatocrit is higher in infants and

droppped with age . An acid steatocrit of less than 10% is indicative of steatorrhea in children.

Continue …….

fatty layer length in cm

(

fatty layer length in

cm +

solid layer

length)

X100

Raed Z. Ahmed, Medical Parasitology Lab.,2012-2013Slide16

Calculate the fecal fat in grams per 24 hours.In adult:Fecal

fat in g/24 hrs.= [0.45 X acid steatocrit %] – 0.43

In children up to 15 years:Fecal fat in g/24 hrs.=

[0.1939

X acid

steatocrit %

] – 0 .2174Continue …….Raed Z. Ahmed, Medical Parasitology Lab.,2012-2013