Performing a Fecal Examination
Posted: Monday, March 25th, 2024 | Updated: Monday, March 25th, 2024
Posted: Monday, March 25th, 2024 | Updated: Monday, March 25th, 2024
Sample Collection and Storage
A fecal examination ideally requires a fresh stool sample typically less than two hours old. Refrigeration of the sample is recommended if the examination can't take place until later on. Samples may be stored for up to approximately two months under proper refrigeration. They should be free of any environmental debris such as cat litter, gravel, etc. If able, the sample size collected should be about 2-5 grams.
Obtaining a Diagnostic Sample
Samples collected for fecal examination may be collected directly and gently from the rectum with proper PPE or indirectly from the environment.
Sample Handling
It's of the utmost importance when working with any bodily fluid or production to wear the appropriate PPE to avoid exposure to any zoonotic diseases. At minimum, work with clean surfaces and utilize gloves.
Fecal Colors
Fecal Flotation Procedure (Passive and Centrifugal)
In order to perform a fecal flotation, you will need a microscope, microscope slides, a cover slip, feces, a container to easily float the fecal sample (ex. a fecalizer), and either a zinc sulfate solution (SG: 1.18), a Sheather's sugar solution (SG: 1.25-1.27), or a sodium nitrate solution (SG: 1.20-1.33). Solutions with a specific gravity of >1.20 will float heavier eggs (ex. whipworm eggs) and solutions with a specific gravity of <1.20 will be more likely to float protozoal organisms (ex. Giardia cysts). Zinc sulfate solutions are best used to float lungworm larva such as Aelurostrongylus Abstrusus. To begin, place the fecal sample into the delegated float container. Add a small amount of the flotation solution. Gently and thoroughly mix and breakdown the fecal matter. Further dilute the mixture by adding more of the flotation solution until a meniscus is visible at the top of the container. Carefully place a coverslip on top of the meniscus. Try not to spill the sample when doing so. Leave the coverslip in place and undisturbed for about 15 to 20 minutes. At this point, the eggs should have floated to the top. Remove the coverslip and place it on the microscope slide. Examine the sample for any parasite eggs or protozoal oocysts/cysts. You may scan the slide using the 10x or 40x objective lenses.
For a more accuracy or reliability, centrifugal flotation may be utilized instead of passive flotation. Begin by placing a sample into a container of your choosing to mix the fecal matter with the flotation solution. Gently and thoroughly mix and breakdown the fecal matter. Pour the sample into a centrifuge tube by passing it through a kitchen or tea strainer. A funnel may help you pass the sample into the smaller tube. Further dilute the mixture by adding more of the flotation solution. Slowly fill the tube to a level that is full enough to where the sample will just avoid making contact with the cap while centrifuging. Properly balance the sample and centrifuge for three to five minutes at 1000 to 1500 RPM. Carefully remove the tube trying not to disturb the mixture. Slowly drop more flotation solution into the tube near the edge. Fill the tube until a meniscus is visible at the top of the container. Carefully place a coverslip on top of the meniscus. Try not to spill the sample when doing so. Leave the coverslip in place and undisturbed for about 10 to 20 minutes. At this point, the eggs should have floated to the top. Remove the coverslip and place it on the microscope slide. Examine the sample for any parasite eggs or protozoal cysts/oocysts. You may scan the slide using the 10x or 40x objective lenses.
Direct Smear Procedure
In order to perform a direct smear, you will need a microscope, microscope slides, and a fresh fecal sample. You may find that using a wooden applicator tip to collect and spread the fecal sample on the microscope slide works the best. Only use a small amount of sample. Spread the sample across the slide by gently rolling the applicator stick back and forth. You're slide should still be semi-transparent in color. If it's not transparent at all, you've likely placed too much sample on the slide. Let the slide air dry completely. Once dried, you may fix and stain the slide using a product like Diff-Quik. When examining the slide, you may see some eggs, bacteria, and/or giardia cysts on higher objectives. When viewing at 100x magnification, be sure to use oil immersion.
Wet Mounted Fecal Examination Procedure
In order to perform a wet mounted exam, you will need a microscope, microscope slides, a coverslip, a fresh fecal sample, and normal saline. On the microscope slide, mix a small amount of fresh feces with a couple small drops of normal saline. You may find that using a wooden applicator stick is helpful to mix the sample. The mixed sample should be semi-transparent in color. Place a coverslip on the area of the slide you made your mixture. Examine at various objectives. You are likely to see giardia cysts with this method. You may also occasionally see a trophozoite. A sample mixed with Lugol's iodine may help visualize cysts. Additionally, creating a darker field by lowering the condenser lens may help visualize the cysts.
A fecal examination ideally requires a fresh stool sample typically less than two hours old. Refrigeration of the sample is recommended if the examination can't take place until later on. Samples may be stored for up to approximately two months under proper refrigeration. They should be free of any environmental debris such as cat litter, gravel, etc. If able, the sample size collected should be about 2-5 grams.
Obtaining a Diagnostic Sample
Samples collected for fecal examination may be collected directly and gently from the rectum with proper PPE or indirectly from the environment.
Sample Handling
It's of the utmost importance when working with any bodily fluid or production to wear the appropriate PPE to avoid exposure to any zoonotic diseases. At minimum, work with clean surfaces and utilize gloves.
Fecal Colors
- Varying shades of brown: This is typically the normal stool color
- Dark black and tarry in texture: This may indicate bleeding in the upper gastrointestinal tract (i.e. stomach/small intestine)
- Bright red or maroon: This may indicate bleeding in the lower gastrointestinal tract (i.e. large intestine/colon)
- Yellow, grey, greyish white: This may indicate a problem with the liver, pancreas, and/or gallbladder
- White: This may indicate a diet too high in calcium (ex. eating bones/eggshells)
- Other: Sometimes medications, food, and other food sources may effect the color of the stool as well. Pet foods that are black in color may lead to dark brown to black stools also. Pets that receive barium may experience white stools at some point and pets that receive activated charcoal may experience black stools at some point. A pet with tapeworms may produce stool with white spots or specks. Lastly, a pet that has eaten grass may likely pass that along undigested in their stool.
Fecal Flotation Procedure (Passive and Centrifugal)
In order to perform a fecal flotation, you will need a microscope, microscope slides, a cover slip, feces, a container to easily float the fecal sample (ex. a fecalizer), and either a zinc sulfate solution (SG: 1.18), a Sheather's sugar solution (SG: 1.25-1.27), or a sodium nitrate solution (SG: 1.20-1.33). Solutions with a specific gravity of >1.20 will float heavier eggs (ex. whipworm eggs) and solutions with a specific gravity of <1.20 will be more likely to float protozoal organisms (ex. Giardia cysts). Zinc sulfate solutions are best used to float lungworm larva such as Aelurostrongylus Abstrusus. To begin, place the fecal sample into the delegated float container. Add a small amount of the flotation solution. Gently and thoroughly mix and breakdown the fecal matter. Further dilute the mixture by adding more of the flotation solution until a meniscus is visible at the top of the container. Carefully place a coverslip on top of the meniscus. Try not to spill the sample when doing so. Leave the coverslip in place and undisturbed for about 15 to 20 minutes. At this point, the eggs should have floated to the top. Remove the coverslip and place it on the microscope slide. Examine the sample for any parasite eggs or protozoal oocysts/cysts. You may scan the slide using the 10x or 40x objective lenses.
For a more accuracy or reliability, centrifugal flotation may be utilized instead of passive flotation. Begin by placing a sample into a container of your choosing to mix the fecal matter with the flotation solution. Gently and thoroughly mix and breakdown the fecal matter. Pour the sample into a centrifuge tube by passing it through a kitchen or tea strainer. A funnel may help you pass the sample into the smaller tube. Further dilute the mixture by adding more of the flotation solution. Slowly fill the tube to a level that is full enough to where the sample will just avoid making contact with the cap while centrifuging. Properly balance the sample and centrifuge for three to five minutes at 1000 to 1500 RPM. Carefully remove the tube trying not to disturb the mixture. Slowly drop more flotation solution into the tube near the edge. Fill the tube until a meniscus is visible at the top of the container. Carefully place a coverslip on top of the meniscus. Try not to spill the sample when doing so. Leave the coverslip in place and undisturbed for about 10 to 20 minutes. At this point, the eggs should have floated to the top. Remove the coverslip and place it on the microscope slide. Examine the sample for any parasite eggs or protozoal cysts/oocysts. You may scan the slide using the 10x or 40x objective lenses.
Direct Smear Procedure
In order to perform a direct smear, you will need a microscope, microscope slides, and a fresh fecal sample. You may find that using a wooden applicator tip to collect and spread the fecal sample on the microscope slide works the best. Only use a small amount of sample. Spread the sample across the slide by gently rolling the applicator stick back and forth. You're slide should still be semi-transparent in color. If it's not transparent at all, you've likely placed too much sample on the slide. Let the slide air dry completely. Once dried, you may fix and stain the slide using a product like Diff-Quik. When examining the slide, you may see some eggs, bacteria, and/or giardia cysts on higher objectives. When viewing at 100x magnification, be sure to use oil immersion.
Wet Mounted Fecal Examination Procedure
In order to perform a wet mounted exam, you will need a microscope, microscope slides, a coverslip, a fresh fecal sample, and normal saline. On the microscope slide, mix a small amount of fresh feces with a couple small drops of normal saline. You may find that using a wooden applicator stick is helpful to mix the sample. The mixed sample should be semi-transparent in color. Place a coverslip on the area of the slide you made your mixture. Examine at various objectives. You are likely to see giardia cysts with this method. You may also occasionally see a trophozoite. A sample mixed with Lugol's iodine may help visualize cysts. Additionally, creating a darker field by lowering the condenser lens may help visualize the cysts.
Sources:
Haller, JoLynn. "The Veterinary Nurse's Guide to Fecal Flotation Techniques" Today's Veterinary Nurse. Fall 2021, https://todaysveterinarynurse.com/clinical-pathology/the-veterinary-nurses-guide-to-fecal-flotation-techniques/
Wortinger, Ann. "Giardiasis in Cats" Today's Veterinary Nurse. Summer 2021, https://todaysveterinarynurse.com/parasitology/giardiasis-in-cats/
Haller, JoLynn. "The Veterinary Nurse's Guide to Fecal Flotation Techniques" Today's Veterinary Nurse. Fall 2021, https://todaysveterinarynurse.com/clinical-pathology/the-veterinary-nurses-guide-to-fecal-flotation-techniques/
Wortinger, Ann. "Giardiasis in Cats" Today's Veterinary Nurse. Summer 2021, https://todaysveterinarynurse.com/parasitology/giardiasis-in-cats/