The importance of fecal testing

There is a wealth of information that can only be found in a direct fecal analysis that will not be possible in a “floated” sample

Photos courtesy Cade Wilson

Stool samples, a fecal analysis, parasite screenings, a “poop check.” It does not matter what you call it, if you work in a veterinary hospital, it is not the most popular test. Yet, they are performed, most likely, multiple times a day. They give a practitioner a wealth of knowledge, if done correctly, that cannot be discovered by any other means.

I have practiced long enough that I have seen these performed in multiple ways. Some are done very well, and others are completed with poor techniques that make diagnosis of disease and parasites more difficult, not easier. The goal of this article is to make you think through how these tests are performed within your clinic. Is there a protocol? From one patient to the next, how confident are you in the samples you or your staff are evaluating? How much of that information is making it into the files? When I speak with other veterinarians, veterinary technicians, and veterinary assistants, I often ask questions about what they are looking for within certain tests. The answers are often very interesting. This goes for when I read through old records for new patients in my veterinary practice. “No Parasites Found (NPF)” is the only thing written on 90 percent of records under results of a “fecal.” Seriously, that is the only take away they got from the test?

Chock full of info

A fecal analysis may be performed for a wide range of reasons. On any given day, we could be reviewing a sample from a healthy pet, a sick kitten with coccidia, a sock-stuffed goldendoodle, or a yet-to-be diagnosed parvo puppy, and that is just in the morning. All those scenarios have their own distinct colors, textures, and smells.

The notes associated on three of the four of the charts should not say, NPF. Yes, technically, that would be a true statement, but there is so much more information that can be added to the patient record. Adding in the descriptors will not only help with the diagnosis during this visit, but also aid in what is normal for this specific patient down the road.

What else should I be adding in my patient record, you might ask? Well, paint me a picture with your description so I can see in my mind what you are describing. What was the consistency? Color? Amount? What did the direct analysis look like under the microscope? What did the “float” look like? Were the number of bacteria present normal or excessive? Were the bacteria alive or not? Were parasites observed? If so, how many? What kind? Did you have a diagnostic sample, or did you only get a smeared fecal loop? These things impact the ability to make an accurate, definitive diagnosis, and they should matter to you.

Size your sample

Coccidia under a microscope.

Let’s start at the beginning. How much sample are you working with and how was it obtained? In a perfect world, the owner delivers you a diagnostic sample from home. This might be in a baggie, a plastic tub, or a sample cup picked up from your clinic prior to the appointment, but hopefully not soaked up in a paper towel (Yes, I have seen that one, too).

A diagnostic sample is something more than a gram of stool. Early in my veterinary school career, it was explained to me that this is about the size of a sugar cube. A gram of stool should be equal to a full teaspoon.

When in doubt, use more, as too much of a sample is not a problem in this case. Too small of a sample size, though, can and will get you in trouble. Fecal loops can be used for collection of fecal samples, but remember, volume matters. One fecal loop worth of stool is not going to be enough for the diagnostic sample. When using a fecal loop, do not put so much “lube” that it fills the opening from where the fecal material is to be collected. I have seen this performed, and it will not yield the best sample.

Give a thorough description

Now that you have a sample to work with, it is time to begin the description. You can start with something as easy as saying you received a diagnostic sample: anything more than a gram or teaspoon or less than an adequate diagnostic sample. Adding this information at the beginning of the record will be helpful to anyone reviewing these notes in the future. If you are not able to make a confirmed diagnosis after the physical examination and fecal analysis, you need to be able to go back in time and know without a shadow of a doubt the sample size was not part of the problem.

If the patient continues to have digestive issues and you see there was not enough material for a proper fecal analysis originally, then you know another fecal analysis must be completed. However, if the notes only say NPF, then you cannot make that determination. Often, you may be the one going back to these notes. Help yourself out by being very descriptive from the initial analysis and not having to rely on your memory.

After documenting the volume of the sample, the color of the stool should be described next. Black, brown, tan, yellow, red, white; it matters and should be added to the notes. If I only told you the color of the stool sample we are working with, I bet you are already adding problems to the differential diagnosis list and likely excluding others. What if I told you I had a schnauzer patient with bright red stool? What are your thoughts? How about a 10-week-old kitten with yellow diarrhea? Okay, now a 13-week-old puppy with black stool? If your differential list began with hemorrhagic gastroenteritis (HGE), coccidia, and then hookworms from those three made-up scenarios, we are on the same page. If the notes do not have the color, then you just made your next decisions more difficult than they needed to be.

Check consistency

Hookworms under a microscope.

Consistency of the bowel movements is also something I see excluded in the notes that I believe is very important. There are many ways this can be documented. You could use words that are agreed upon within your specific veterinary practice, use descriptive words that are determined case-by-case, or use a numbering system that can be easily added to the chart. Purina has a scoring system that uses a one to seven numerical code with a handy picture guide that is easily obtained (this guide also makes a very good white elephant gift when framed). Descriptions such as watery, solid, or jelly-like stools can be very helpful in localizing what is going on in the digestive tract for the patient you are examining. There have been many times in my professional career, where I have had to dig through the clinic trash to “know” the answer to what the consistency was for a specific case. This is not on my list of top 10 favorite things to do. Write down the consistency for your future self or for whomever may be taking the next step in diagnostics for the case in question. There are very few things grosser than the trash can in a vet hospital where the fecal samples are thrown away!

Start analysis

The first round of documentation for your analysis is now complete. It has been documented that there is, or is not, a diagnostic sample. The color and the consistency of the sample is known before microscopic observations.

I personally believe the microscopic analysis is a two-step process. It should start with a “direct sample” placed on a slide with a drop of sterile saline. This is done to look at the bacterial colonies, types of bacteria present, health of the normal gut bacteria, to look for cells such as red blood cells, evaluate the food particles present, look for foreign debris such as grass, and for the presence of parasites and parasitic ova.

This is likely where you will find things such as giardia or certain tapeworms. This is also a good time to break open that proglottid that was found under your patient’s tail when getting that sample in the exam room and add it to the direct sample. Having information to assist in proving to the client you are dealing with Dipylidium tapeworms (which proves the pet ate a flea) backs up your recommendation for flea prevention.

There is a wealth of information that can only be found in a direct fecal analysis that will not be possible in a “floated” sample. The takeaway is the benefits that result from taking a couple of extra minutes in better describing and documenting your fecal analysis before and after looking at your microscope. Taking your time to truly evaluate what is normal and abnormal with each pet visit and document in the client record will save you time and increase your effectiveness in the long run.


Be as thorough with your fecal analysis as you can—including timekeeping and notetaking from the “float” stage onwards.

Not all protocols for this are equal and here are my personal tips to make this as productive as possible:

1) Obtain appropriate sample size. This is where at least one gram, or a full tablespoon, is required. Anything less means you could be missing something.

2)  Mix with a high-density solution. There are several varieties available that can be purchased or produced in office, but zinc sulfate and Sheather’s sugar solutions lead the pack. Zinc sulfate has a specific gravity of 1.18, and the Sheather’s sugar solutions will have a specific gravity greater than 1.27. These both, given enough time, will float the heaviest of parasite ova found in the patients of a small animal practice.

I use a premade sugar solution within my practice, that has a 1.27 specific gravity and I am very satisfied with its results. Your ability to diagnosis parasites such as Trichuris sp. will skyrocket when using these.

3)  Centrifuge your samples. There is no doubt this is a better method and after doing side-by-side tests more than 15 years ago, I will not be going back to non-centrifuged samples.

Cade M. Wilson, DVM, is a practicing veterinarian and a three-doctor mixed-animal practice owner in Ardmore, Okla. He has been practicing small animal medicine for the last 18 years and been a practice owner for the last 15 years.

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