Fecal Analysis
Composition and characterstics of feces :feces consist mainaly of cellulose and other undigested foodstuff ,bacteria ,and water (as much as 70 percent ).Other substances normally found in stools include epithelial cells shed from the gastrointestinal tract ,small amount of fats ,bile pigmentsin the forms of urobilin ,gastrointestinal and pancreatic secretion ,and electrolytes.
The average adult excretes 100to 300g of fecal material per day, the residue of approximately 10 L of liquid material that enters the intestinal tract each
Feces are normally brown because of bacterial degradation of bile pigments to stercobilin .the characteristic odor of feces is caused by bacterial action on proteins and other residues that produce substances such as indole ,skatole,phenol,hydrogen ,sulfide,and ammonia.the normal consistency of feces is described asplastic that is ,stoolsshould not normally be liquid ,mushy,or hard.
The shape and caliber of normallstools is the same as that of the distal colon
Alteration in color ,odor,consistency or shape may indicate the presence of disease.Although these characteristic are not always specifically studied in the laboratory.
Laboratory analysis of feces includes microscopic examination ,chemical tests for specific substances,and microbiologic tests .
Laboratory analysis of feces is performed much less frequently than are studies of blood ,urine and other body fluids.
One reason for this is that client and health –care providers dislike collected stool specimens
Leucocytes :E xamination of feces for leucocytes ,especially neutrophils and monocytes,is usually performed in the initial evalution of diarrhea of unknown etiology .Testing for the presence or absence of leucocytes can provide important diagnostic clue and these yield results faster than do stool.
Epithelial cells:normally small to moderate numbers of epithelial cells are presents in feces .Large number of epithelial cells (or large amount of mucus),however ,indicate ihat the intestinal mucosa is irritated.
Qualitative fats :Fats are found in the feces primarily in the formsof triglycerides (neutral fats),fatty acids, and fatty acids salts .Their presence is determined through various staining techniques before microscopic examination .through these methods,the number of fat droplets and their size can be determined ,and the type of fat can be identified .The finding of more than 60 fat droplets per high –power field(HPF)usually indicates steatorrhea which simply means excess fat in the stool.
The size of the droplets also must be considered in arriving at adiagnosis .the fat droplets in steatorrhea are usually larger than normal.
Excess fat in the stool is usually caused by either malabsorption syndromes or deficiency in pancreatic enzymes .Microscopic examination for fecal fat may aid in differentiating between these two disorders .An increase in triglycerides generally indicates adeficiency of pancreatic enzymes that normally breakdown triglycerides to fatty acids .In contrast ,individuals with malabsorption syndromes usually have normal amount of triglycerides in their stools but excessive fatty acids because these clients are unable to absorb the fats once they are broken down .Othercauseso of excessive fecal fat include surgical resection of fistulas of the intestines and recent intake of excessive amount of dietary fats.
False negative results may occur in individuals with malabsorption problems who restrict their fat intake because of enorexia.
Microscopic tests for fecal fats are essentially qualitative in nature .the test simply indicates whether excessive fat in present and ,if so ,the nature of that fat.The definitive test for evaluating steatorrhea is quantitative analysis for fecal fat .This eevalution is aaccomplished through a72 –hour stool collection while the client is on adietcontaining 100g of fat per day.