Macroscopic examination of stool specimen

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stool specimen

Once a stool specimen is received in the medical laboratory, the analytic phase of laboratory testing is initiated which is refers to as processing. The stool specimen is examined from two perspectives that is, Macroscopic and microscopic. In this article, we shall be talking about the macroscopic examination of stool.

Macroscopic examination of stool specimen

Stool sample is first examined macroscopically in order to determine its consistency and color. To perform this task, the laboratory technician or scientist must make sure to receive a fresh and unpreserved stool sample. The stool sample is also screened and examined for the presence of gross abnormalities. Whether heterogeneous (mixed with other elements) or homogeneous.

In this article, we shall discuss on the three macroscopic features of stool taken into consideration during macroscopic examination of stool that is, Consistency, Color and Gross abnormalities.

Consistency of stool specimen

Stool consistency also referred to as the degree of moisture may serve as an indicator of the presence of a parasite. I once remember seeing a motile protozoan trophozoites (Entamoeaba histolytica) in a watery stools from a child. Protozoan’s cysts such as Entamoeba coli are more likely to be found in formed stools. I once saw strongyloides stercolaris ova and larva in formed stool of a kitten.

Consistency is also useful in defining constipation as with hard or formed stools and diarrhea with water stool or liquid stools.

Color of stool specimen

During macroscopic examination of stools, the color of the stool sample is of great consideration. Pale or clay colored stools sample may be indicative of a problem with the drainage of your biliary system or the presence of excessive fat in stools (steatorrhea).Protozoans such as Giardia lamblia is commonly found in pale stools. Yellow stool could be as a result of pancreatitis.

The range of stool colors varies, including black (tarry) to green to clay, and colors in between. The color of normal stool is brownish meanwhile unusual stool colors are purple, red, or blue, typically suggest that the patient is on a particular medication.

Gross abnormalities of stool

Adult worms, proglottids, pus, and mucus are some of the potential gross abnormalities found in stool. To begin, look for parasites such as pinworms, tapeworm proglottids, and adult worms on the surface of the stool. After that, the sample should be broken up with a wooden applicator stick and examined again for macroscopic parasites, especially adult helminths.

Other macroscopic abnormalities in the specimen may indicate parasitism. Blood and/or mucus in loose or liquid stool, for example, may indicate the presence of amebic ulcers in the large intestine. Irritation and bleeding are commonly associated with bright red blood on the surface of a formed stool.

A number of possible terms may be used to describe the macroscopic appearance of a stool specimen. A suggested list of possible consistency, color, and gross abnormalities descriptions is found in table below

Consistency TermsPossible ColorsGross Appearance Terms
HardDark brownConspicuously fibrous
SoftBlackFiber scanty to
moderate
MushyBrownColloidal
(homogeneous)
LoosePale brownScanty mucus
DiarrheicClayMuch mucus
Watery, liquidYellowMucus with scanty
blood
FormedRed-brownOther (e.g., blood,
barium)
Semi-formedGreen,
other
 
list of possible consistency, color, and gross abnormalities

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