King Saud University
College of Science
Department of Biochemistry
Disclaimer
 The texts, tables and images contained in this course presentation (BCH
376) are not my own, they can be found on:
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Chapter 17
Fecal Analysis
Professor A. S. Alhomida
1
Fluid Regulation in GI Tract
1. Approximately 900 mL of ingested fluid, saliva,
gastric, liver, pancreatic, and intestinal secretions
inter the digestive tract each day
2. 500-1500 mL of this fluids reaches the large
intestine, and only about 150 mL is excreted in the
feces (stool)
2
Fluid Regulation in GI Tract,
Cont’d
3. Water and electrolytes are absorbed in both small and
large intestines
4. Large intestine can absorb about 300 mL of water,
when the amount of water exceeds this amount is
excreted in the feces producing diarrhea
3
Fluid Regulation in GI Tract
4
Specimen Collection
1. Routine Specimens
•
Qualitative Testing
2. Timed Specimen
•
Quantitative Tests
5
Composition of Feces on an
Average Diet
Component
% of Total Weight
Water
75
Solid
25
% of Total Solids
Cellulose & Other Indigestive Fiber
Variable
Bacteria
30
Inorganic Material (mostly Ca & Ph(
15
Fat & Fat Derivatives
5
6
Fecal Analysis Tests
1. Macroscopic Screening
•
•
Color
Appearance
2. Microscopic Examination
•
•
•
Fecal Leukocytes
Muscle Fibers
Qualitative Fecal Fats
(Steatorrhea)
7
Fecal Analysis Tests, Cont’d
3. Chemical Tests
1. GI Tract Bleeding (Occult Blood )
2. Quantitative Fecal Fat Tests
3. Fetal Hemoglobin (Apt Test)
4. Fecal Enzymes
8
Fecal Analysis Tests
Chemical Tests, Cont’d
5. Carbohydrates
6. Liver diseases
7. Biliary duct disorders
8. Maldigestion and Malabsortion Syndromes
9. Inflammation
9
Fecal Analysis Tests
10
Macroscopic Screening Tests
11
Fecal Screening Tests
12
Fecal Pigments
1. Normal color of feces is influenced by both amount
of uroblin present and the kind of food taken
2. Largely vegetable diet gives light-colored stools
while one rich in meats gives darker, brown color
13
Fecal Pigments, Cont’d
3. Undigested portions of some vegetables may color
the stools
•
Carrots
Reddish-brown
•
Spinach
Greenish
•
Fruits
Bilberries, grayish-purple
•
Milk diet
Pale-yellow or Orange
14
Abnormality of Fecal
Compositions
• Steatorrhea
1.Abnormality of absorption and digestion of lipids
2.It occurs when obstruction of flora of bile due to the
biliary obstruction
3.Leads to increase fat content of stools
15
Abnormality of Fecal
Compositions, Cont’d
•
Occult Blood
1. When bleeding is severe, the stools are dark color
2. Bleeding > 2.5 mL/150 g of stool is considered
pathologically significant
3. In intestine, oxyhemoglobin is converted to hematin and
porphyrins
4. Only hematin gives +ve results with fecal occult blood test
5. Ulcers and cancers of color give +ve results
16
Occult Blood Tests
17
THE END
Any questions?
18