Sandbox:VD

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Vishal Devarkonda, M.B.B.S[2]

Overview

A stool analysis is a series of tests done on a stool (feces) sample to help diagnose certain conditions affecting the digestive tract  These conditions can include infection (such as from parasites, viruses, or bacteria), poor nutrient absorption, or cancer.

For a stool analysis, a stool sample is collected in a clean container and then sent to the laboratory. Laboratory analysis includes microscopic examination, chemical tests, and microbiologic tests. The stool will be checked for color, consistency, amount, shape, odor, and the presence of mucus. The stool may be examined for hidden (occult) blood, fat, meat fibers, bile, white blood cells , and sugars called reducing substances. The pH of the stool also may be measured. A stool culture is done to find out if bacteria may be causing an infection.

Indications

Common indication for stool analysis in general practice are

• Help identify diseases of the digestive tract, liver , and pancreas . Certain enzymes (such as trypsin or elastase) may be evaluated in the stool to help determine how well the pancreas is functioning.
• Help find the cause of symptoms affecting the digestive tract, including prolonged diarrhea, bloody diarrhea, an increased amount of gas, nausea, vomiting, loss of appetite, bloating, abdominal pain and cramping, and fever.
• Screen for colon cancer by checking for hidden (occult) blood.
• Look for parasites, such as pinworms or GiardiaGiardia.
• Look for the cause of an infection, such as bacteria, a fungus, or a virus.
• Check for poor absorption of nutrients by the digestive tract (malabsorption syndrome). For this test, all stool is collected over a 72-hour period and then checked for fat (and sometimes for meat fibers). This test is called a 72-hour stool collection or quantitative fecal fat test.

Specimen collection

Advice the patient to urinate and put on gloves to gloves(prevent infection) before collection of stool. Ask the patient to pass stools in a given dry container and close the container with a lid and label it with name, time, and date.

CDC recommendations for stool collection for laboratory identification of parasitic diseases of public health concern

• Collect the stool in a dry, clean, leakproof container. Make sure no urine, water, soil or other material gets in the container.
• The image on the right demonstrates the distribution of protozoa in relation to stool consistency and should be taken into consideration when specimens are received.
• Fresh stool should be examined, processed, or preserved immediately.  An exception is specimens kept under refrigeration when preservatives are not available; these specimens are suitable for antigen testing only.
• Preserve the specimen as soon as possible.  If using a commercial collection kit, follow the kit's instructions.  If kits are not available, the specimen should be divided and stored in two different preservatives, 10% formalin and PVA (polyvinyl-alcohol), using suitable containers.  Add one volume of the stool specimen to three volumes of the preservative.
• Insure that the specimen is mixed well with the preservative.  Formed stool needs to be well broken up.
• Insure that the specimen containers are sealed well.  Reinforce with parafilm or other suitable material.  Insert the container in a plastic bag.
• Certain drugs and compounds will render the stool specimens unsatisfactory for examination.  The specimens should be collected before these substances are administered, or collection must be delayed until after the effects have passed.  Such substances include: antacids, kaolin, mineral oil and other oily materials, non-absorbable antidiarrheal preparations, barium or bismuth (7-10 days needed for clearance of effects), antimicrobial agents (2-3 weeks), and gallbladder dyes (3 weeks).
• Specimen collection may need to be repeated if the first examination is negative.  If possible, three specimens passed at intervals of 2-3 days should be examined.

Preservation of specimens

• Preservation of specimens is necessary when stool specimens cannot be examined within the prescribed time interval. Various preservatives are available, with the two most commonly used being 10% aqueous formalin and PVA (polyvinyl-alcohol). 

Analysis

Appearance

Shape and consistency

Bristol Stool Chart

The shape and consistency of stool depend with good statistical correlation from the time of permanence of the same in the colon. Bristol stool chart based on shape and consistency classifies stool into seven categories. Bristol stool scale is part of the diagnostic triad for irritable bowel syndrome.

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Color

Color	Inference
Light to dark brown	Normal
Green stool	Consumption of green leafy vegetables Green food coloring Food may be moving through large intestine quickly
Red	Lower gastrointestinal tract bleed Red food coloring
Black	Upper gastrointestinal tract bleed(Melena) Intake of Vitamins containing iron and bismuth subsalicylate
White	Bile duct obstruction Colored food sometimes may cause it

Chemical test

PH
Electrolytes
Osmolarity
Antigen essay
Fat
Blood
Bile