Assessing the Physical Properties of Fecal Matter

Assessing the Physical Properties of Fecal Matter

Ryane E. Englar

16.1 Procedural Definition: What Is This Test About?

Fecal analysis is a diagnostic test that involves both macroscopic and microscopic examination of the patient’s sample. Fecal samples are routinely obtained via “free catch,” meaning that a fresh sample is collected after the patient defecates. In dogs, this is most often achieved by picking up after the patient on leashed walks. Stool samples may be gathered with gloved hands or through a baggie that has been turned inside out to facilitate collection. Because we are essentially picking up the stool from the ground, samples frequently contain plant material, sand, dirt, or pebbles (see Figures 16.1 and 16.2).

In cats, feces are obtained by scooping the litterbox, in which case, the resultant sample is often encased with litter (see Figure 16.3).

Diarrheic samples from either species are more difficult to gather and may require serial collection to obtain sufficient material for testing (see Figure 16.4).

Occasionally, veterinarians elect to obtain fresh samples of feces during the physical examination with the assistance of a fecal loop (see Figure 16.5) [1]. This pencil‐sized polyethylene wand has a slotted end that is lubricated prior to insertion into the rectum. The looped end traps fecal material if it is present within the rectum. Following extraction of the tool from the rectum, the trapped fecal matter can be analyzed. Alternatively, veterinarians may sample feces by inserting a gloved finger into the rectum during rectal palpation. Fecal matter that adheres to the gloved finger can be evaluated following rectal examination for both macroscopic and microscopic features.

Fecal analysis begins with a macroscopic assessment of the sample. The sample is characterized in terms of its physical properties. This chapter will concentrate on the following physical properties of feces:

  • consistency
  • color
  • presence/absence of blood
  • presence/absence of mucus
  • gross parasitism
  • odor.

Subsequent chapters (see Chapters 17 and 18) will introduce microscopic assessment of feces, that is, what is traditionally thought of as fecal analysis.

16.2 Procedural Purpose: Why Should I Perform This Test?

The evaluation of feces is a critical diagnostic tool that is used in the detection and management of a variety of medical conditions ranging from localized gastrointestinal disease (e.g. small and large bowel endoparasitism) to metabolic dysfunction (e.g. exocrine pancreatic insufficiency [EPI]).

Physical characteristics of feces also provide clues about the health of seemingly unrelated body systems. For example, rock hard fecal balls may reflect prolonged retention of feces within the lower digestive tract due to orthopedic challenges that make posturing to defecate difficult (e.g. osteoarthritis).

Fecal analysis is an essential part of screening patients, especially puppies and kittens, for endoparasites, many of which are zoonotic [2, 3].

In 2018, a research team led by Caroline Sobotyk analyzed 4692 fecal flotation test results from 10 veterinary diagnostic laboratories in nine states in the United States [4]. Samples came from client‐owned dogs as well as research and shelter dogs [4]. One‐fifth of samples were positive for one or more parasites [4]. Giardiasis was confirmed in 8.33% of samples followed by parasites within the family Ancylostomatidae, Cystoisospora spp., Toxocara canis, and Trichuris vulpis, in order of prevalence [4].

Photo depicts an example of loose canine feces prior to being sampled.

Figure 16.1 Example of loose canine feces prior to being sampled. Note that this sample contains maggots and is seated against a backdrop of grass. Once gathered from the ground, this sample is likely to contain plant material as an incidental finding.

Source: Courtesy of Ryane E. Englar, DVM, DABVP (Canine and Feline Practice).

Photo depicts an example of semi-formed canine feces prior to being sampled.

Figure 16.2 Example of semi‐formed canine feces prior to being sampled. Note that this sample contains tapeworms and is seated against a backdrop of snow and decaying leaves. Once gathered from the ground, this sample is likely to contain plant material as an incidental finding.

Source: Courtesy of Michelle Lugones, DVM.

A 2020 study by Stafford et al. specifically studied fecal samples from canine patients that frequent dog parks within the United States [5]. Stafford found that, again, one‐fifth of the sample population was infected with one or more intestinal parasites [5]. Moreover, of the dog parks that were studied by the research team, 85% were contaminated with intestinal parasites [5].

Identification of endoparasites, particularly within asymptomatic patients, is of utmost importance when managing public health and maintaining the human–animal bond.

Photo depicts an example of formed feline feces prior to being sampled.

Figure 16.3 Example of formed feline feces prior to being sampled. Note that this sample is contained within a litterbox. Once sampled, this sample will contain litter as an incidental finding.

Source: Courtesy of Ryane E. Englar, DVM, DABVP (Canine and Feline Practice).

Photo depicts an example of diarrheic feces from a puppy.

Figure 16.4 Example of diarrheic feces from a puppy. This gelatinous fecal matter will be challenging to sample and may require multiple attempts to obtain sufficient volume for analysis.

Source: Courtesy of Ryane E. Englar, DVM, DABVP (Canine and Feline Practice).

The zoonotic potential associated with ascarids is a significant concern [612]. At least 750 cases of uveitis, vision loss, and blindness in people in the United States are attributed to toxocariasis annually [7, 9, 11]. Children are particularly at risk because they are more likely to play in and ingest dirt [7].

Photo depicts an example of a polyethylene fecal wand.

Figure 16.5 Example of a polyethylene fecal wand.

Source: Courtesy of Ryane E. Englar, DVM, DABVP (Canine and Feline Practice).

Tapeworms are also zoonotic. People become infected when they ingest whole fleas that contain Dipylidium caninum [1215]. Affected human patients may develop perianal pruritus as they produce tapeworm segments [7].

People may also become infected with tapeworms of Taenia spp. through accidental ingestion of tapeworm eggs after handling contaminated canine feces [7]. Infections are rare but can lead to cyst formation within the central nervous system (CNS), eye, muscle, or subcutaneous tissue [7].

Infection of people with Echinococcus granulosus is also of great concern because this tapeworm causes the development of cystic lesions within viscera [7].

Diagnosis of endoparasitism within companion animals is key to reducing the risk that their owners will contract disease. Furthermore, diagnosis paves the way for parasite treatment and preventative measures to reduce risk of recurrence [2].

According to the 2020 guidelines from the Companion Animal Parasite Council (CAPC), fecal analysis should take place at least four times during the first year of life [16]. However, it is critical to understand that parasite prevention and control does not end once puppies and kittens become adults. CAPC advises that canine and feline patients undergo fecal examinations at least twice per year throughout adulthood [16]. Patient health and lifestyle as well as parasite prevalence within the geographical residence of the patient may further influence frequency of fecal examination [16].

Beyond routine screening, fecal analysis also plays an essential part of the diagnostic workup for those patients that present with aberrant defecation histories and/or clinical presentations including, but not limited to [12]:

  • constipation – prolonged retention of feces within the colon, resulting in infrequent or difficult evacuation of the feces
  • coprophagia – ingestion of fecal matter [17]
  • diarrhea – loose, liquid bowel movements
  • dyschezia – difficult or painful defecation
  • hematochezia – the presence of fresh (red) blood in the stool from lower gastrointestinal bleeds
  • Melena – dark‐colored (often black) tarry feces containing digested blood from upper gastrointestinal bleeds
  • obstipation – inability to evacuate accumulated, dry, hard feces due to diminished or absent function of the large bowel, causing impaction that may extend the entire length of the colon
  • pica – the intentional consumption of nonfood items [18]
  • tenesmus – straining to defecate.

In addition to playing an essential role in diagnosis, fecal analysis allows us to monitor the patient’s response to case management and/or make assessments concerning disease progression. In the ideal world, patients with known endoparasites re‐present for follow‐up examination and feces are resubmitted until samples retest as “negative,” meaning that no ova or parasites are seen. This allows the veterinary team to shift focus from treatment onto parasite prevention.

Routine fecal analysis involves multiple steps:

  1. assessment of stool’s physical features
  2. microscopic examination of feces

    • direct smear/fecal cytology/wet mount (see Chapter 17)
    • fecal flotation (see Chapter 18)

      • passive (gravitational)
      • centrifugal.

There are also a variety of add‐on fecal tests that may be considered on a case‐by‐case basis, depending upon the clinician’s list of differential diagnoses and index of suspicion. For instance,

  • Fecal cultures evaluate the microbial composition and make determinations about treatment in patients that are experiencing dysbiosis.
  • The Baermann technique evaluates patient samples for free‐living parasitic nematode larvae, including, but not limited to, lungworms (in cats, horses, and ruminants primarily) and the canine intestinal threadworm, Strongyloides stercoralis [19].

These add‐on tests are beyond the scope of this text and specifically this chapter, which will concentrate on macroscopic analysis as a guide to characterizing stool based on its physical features.

Gross observations about fecal matter include consistency, color, presence/absence of blood, presence/absence of mucus, gross parasitism, and odor.

16.2.1 Sample Consistency

Fecal consistency is a useful feature because it is one of many indicators of whole‐body hydration and gut transit time. Although each patient has their own version of what constitutes “normal” fecal consistency, in general, canine and feline feces should feel a bit like Play‐Doh – compact with a shape, yet squishable, moist, and easy to pick up. As fecal matter becomes increasingly loose, as from increased water content, it loses shape and leaves a residue behind when it is sampled. At the other extreme is stool that is too firm. As fecal matter dries out, it loses its ability to become compressed. It may become impossible to indent and may trade its log shape for individual pebbles or so‐called fecal balls.

We can discuss fecal consistency with members of the veterinary team, including clients, when we assign a fecal score to the patient’s sample [20]. Because there is no universal fecal scoring system in veterinary practice, many nutritional companies have developed their own [20]. Scores provide accompanying descriptions and an assortment of visual aids that are user‐friendly and get veterinary clients and clinicians on the same page. An example of the Nestlé–Purina fecal scoring system has been provided for your review here (see Figure 16.6).

How to read the fecal score for any given patient sample and what each fecal score might mean in terms of potential etiologies will appear under the subheader, interpretation of test results.

16.2.2 Sample Color

Fecal color is a useful feature because it is one of the many indicators of gastrointestinal health. For example, feces that are yellow‐to‐orange in color may reflect underlying hepatic or biliary dysfunction, whereas feces that are gray and greasy may point toward EPI.

Refer to the subsection below, “Interpreting Test Results,” to consider what various colors of feces may indicate.

16.2.3 Presence/Absence of Blood

Evaluating feces for gross evidence of blood is a useful feature because the presence or absence of blood and whether that blood appears to be fresh or digested localizes disease within the gastrointestinal tract [12].

Refer to the subsection below, “Interpreting Test Results,” to consider how to localize gastrointestinal tract lesions based upon the presence/absence of blood and whether that blood appears to have been digested.

16.2.4 Presence/Absence of Mucous Coating

Evaluating feces for a heavy mucous coating is a useful feature because excessive mucous may be indicative of colonic inflammation, that is, colitis.

Refer to the subsection below, “Interpreting Test Results,” to consider the significance of mucus.

16.2.5 Presence/Absence of Gross Parasitism and Other “Content”

Finding evidence of endoparasites or larvae that can be seen with the naked eye is diagnostic.

Canine and feline fecal samples may contain proglottids (segments) from Dipylidium caninum and Taenia pisiformis, two common tapeworm species [19].

Adult helminths, such as Parascaris equorum, can be found whole in equine feces.

Finding evidence of nonfood items is indicative of pica, that is, the patient is ingesting material that they should not be.

16.2.6 Sample Odor

Clients may present a patient for evaluation of a particularly fetid fecal odor. Alternatively, veterinary team members might smell something unusual in a patient’s sample during fecal analysis that prompts further investigation. It is important not to discount fecal odor because a variety of scents that we are only just now beginning to explore as a profession may indicate a change in the patient’s gastrointestinal health.

Refer to the subsection below, “Interpreting Test Results,” to consider the relevance of odor to fecal analysis.

16.3 Equipment

Gross examination of a fecal sample requires minimal “supplies.” You need only:

  • exam gloves for handling biosamples
  • a fresh sample of feces
  • your eyes to see
  • your fingertips to feel
  • your nose to smell.
Snapshot of fecal scoring system for dogs.

Figure 16.6 Fecal scoring system for dogs.

Source: Courtesy of Nestlé–Purina PetCare.

16.4 Procedural Steps

  1. Obtain a fecal sample from the patient either by “free catch,” rectal examination, or via fecal loop.
  2. Place the fecal sample in an airtight, leak‐proof container with the following details:

    • animal identification (e.g. name and case number)
    • owner identification: (e.g. client last name)
    • date and time of sample collection.

  3. Analyze the fecal sample as quickly as possible but not later than 24 hours after collection to maximize accuracy of the results [19].

    If fecal analysis must be delayed beyond two hours after collection, then refrigerate the sample to slow sample degradation [19, 21].

    Refrigerated samples should not be analyzed beyond 24 hours after collection.

  4. Identify and record the patient’s fecal consistency using the scoring system of your choice.

    Refer to the subsection below, “Interpreting Test Results,” to consider what fecal consistency may indicate.

  5. Identify and record the color of the fecal sample using an appropriate descriptor, including but not limited to:

    1. white
    2. pale to light gray to clay‐colored yellow
    3. yellow, yellow‐orange, orange
    4. green, green‐blue, blue
    5. brown
    6. brown and spotted with white/white speckled/polka dotted
    7. black
    8. red streaks
    9. raspberry jam color.

    Refer to the subsection below, “Interpreting Test Results,” to consider what each color may indicate.

  6. Evaluate the fecal sample for the presence/absence of blood.

    Refer to the subsection below, “Interpreting Test Results,” to differentiate melena from hematochezia and to consider what either may indicate.

  7. Evaluate the fecal sample for the presence/absence of mucus.

    Refer to the subsection below, “Interpreting Test Results,” to consider the significance of fecal mucus.

  8. Evaluate the fecal sample for the presence/absence of macroscopic endoparasites and any other unusual contents.

    Refer to the subsection below, “Interpreting Test Results,” to differentiate common endoparasites that you may see when you assess the fecal sample macroscopically.

  9. Smell the fecal sample and record any unusual features.

16.5 Time Estimate to Perform Test

Less than five minutes.

16.6 Procedural Tips and Troubleshooting

16.6.1 Patient‐Specific Considerations: Important Clues from History‐Taking

Fecal analysis is performed to obtain data about gastrointestinal health; however, results should be considered within the context of the patient’s history and physical exam findings. Historical and physical exam data are especially vital in sick or otherwise unhealthy patients. We may need to encourage the client to share their observations with us using open‐ended questions that ask the client to expand upon the patient’s bowel habits [22]. Examples of open‐ended questions include [20, 22]:

  • “Tell me what you’re noticing at home with respect to your pet’s stool.”
  • “Describe what you’re seeing.”

You may need to clarify key details within the client’s story using closed‐ended questions [22]:

  • “When did the problem begin?”
  • “How long has the problem been going on for?”
  • “What is the problem’s frequency?”
  • “Has this happened before?”
  • “How often does the patient produce a bowel movement?”
  • “When was the patient’s last bowel movement?”
  • “Does your pet strain when passing stool?”
  • Is any stool at all passed?

    • What does the stool look like?
    • What is the stool’s shape and has it changed?

      • Dogs with prostate disease often develop ribbon‐like stools.

  • Is the stool coated with mucus?
  • Is the stool coated with fresh red blood?
  • What is the color of the stool today?
  • What is the color of the stool typically?
  • What is the patient’s fecal score today?
  • What is the patient’s “usual” fecal score?
  • Has the pet’s fecal score changed? If so, how?

If the patient is presenting for evaluation of diarrhea, then the history can help to localize disease.

Large bowel diarrhea is characterized by [12, 23]:

  • gelatinous semi‐formed stool
  • high volume of fecal mucus
  • increased frequency of defecation
  • increased urgency of defecation
  • tenesmus
  • ± hematochezia.

Small bowel diarrhea tends to be voluminous and is associated with weight loss [12, 20, 24, 25]. It typically does not involve fecal mucus, increased frequency of defecation, tenesmus, or dyschezia [12, 2426].

Diet contributes to fecal output, so it is important that we broaden history‐taking to consider what the patient is eating [22, 27]:

  • How is the pet’s appetite?

    • Is the pet still eating?
    • Is the pet’s appetite increased, decreased, or the same?

  • What does the pet eat in terms of food?
  • What does the pet eat in terms of snacks?
  • Has the pet’s diet changed? If so, how?
  • Is the pet unsupervised outdoors?
  • Does the pet have a history of eating plants, dirt, other animals, or other animals’ stool?
  • Does the pet have a history of eating nonfood items?
  • Could the pet have gotten into anything?

Because gastrointestinal health involves both ends of the dog or cat, it is important that history‐taking include whether the pet is keeping food down [22]. Consider asking [22]:

  • Is the pet vomiting?

    • If yes, then ask the client to describe the vomiting:
    • Is the pet really vomiting or is the pet regurgitating?

      • When does vomiting occur relative to eating?
      • When did the vomiting start?
      • What is the frequency? How many times has the pet vomited?
      • Is vomiting productive? Does anything come up?
      • What is the pet vomiting?
      • What color is the vomitus?
      • Does the vomitus contain blood?

Because the act of defecation involves posture, you need to also inquire about the pet’s overall orthopedic health [22]. Past orthopedic disease, such as limb dislocations or pelvic fractures, and ongoing orthopedic disease, including osteoarthritis, may make posturing to defecate challenging [22]. This may lead to incomplete evacuation of feces and constipation [22].

16.6.2 Patient‐Specific Considerations: Important Clues from Physical Examination

A physical examination may provide insight into the likelihood of any orthopedic considerations that may potentiate bowel issues.

Another key feature of the physical examination that should be considered in the context of an elimination history is the patient’s body condition score (BCS). We estimate a veterinary patient’s composition in terms of body fat by assigning them a BCS. There are several different scales for BCS. The author prefers the Purina 9‐point system of body condition scoring (see Figure 16.7). This scale determines BCS by assessing visible and palpable landmarks [28].

According to the Purina 9‐point system [28]:

  • A dog that has a BCS of 1 is emaciated. These dogs have visually prominent ribs, lumbar vertebrae, and pelvic bones that are evident without palpation. There is no palpable body fat and muscle mass is overwhelmingly poor. The waistline is exaggerated. The patient takes on a skeletal appearance.
  • A dog that has a BCS of 2 is moderately underweight, with easily visible ribs, lumbar vertebrae, and pelvic bones; however, when compared with dogs with a BCS of 1, dogs with a BCS of 2 have adequate muscle mass. The abdominal tuck remains pronounced, and there is still no palpable fat.
  • A dog that has a BCS of 3 is mildly underweight. The ribs may or may not be visible, but they are easy to palpate without overlying fat. The pelvic bones, such as the wings of the ilia, are prominent, and the tips of the spinous processes of the lumbar vertebrae are visible. Overall, there is minimal body fat. The waistline is obvious.
  • A dog that has a BCS of 4 may be considered by some to be a “lean normal” or what the author refers to as an “athletic build.” This patient has easily palpable, but not visible ribs, with minimal fat coverage, and a prominent abdominal tuck.
  • A dog that has a BCS of 5 is ideal. These patients are well‐proportioned. They have a visible waist and palpable ribs without an excess of fat coverage.
  • A dog that has a BCS of 6 is slightly overweight. There is a slight excess of fat covering otherwise palpable ribs. One can discern the waist, but it is not prominent.
  • A dog that has a BCS of 7 is mildly overweight. It is possible but challenging to feel the ribcage due to heavy fat coverage, and fat deposits may be starting to accumulate over the lumbar region and tail base. The waist is absent as is the abdominal tuck.
  • A dog that has a BCS of 8 is moderately overweight. It is not possible to feel the ribcage due to heavy fat coverage, and there is no waistline. Fat deposits are easily seen and palpable in the lumbar region bilaterally as well as at the tail base. There may also be visible rounding of the ventral abdomen due to fat deposition.
    Snapshot of assessing canine BCS using the Purina 9-point system.

    Figure 16.7 Assessing canine BCS using the Purina 9‐point system.

    Source: Courtesy of Nestlé–Purina PetCare.

  • A dog that has a BCS of 9 is extremely obese. Fat deposits are extensive: in addition to prominent lumbar “love handles,” fat is present over the neck, thorax, spine, tail, and limbs.

Cats have a similar BCS scoring system through Nestlé–Purina (see Figure 16.8).

BCS is underutilized by the veterinary team [29], yet it is an important screening tool [30] that assists the team in documenting trends. The cat that was once described as being “big‐boned” with a BCS of 7 and is now a BCS of 3 on physical exam, without any identifiable changes in diet or feeding routine at home, requires an extensive diagnostic workup.

Similarly, BCS is an important consideration when the patient presents with an aberrant elimination history. A diarrheic dog or cat that is losing body condition is important data to consider as we perform fecal analysis. In other words, fecal analysis is one of many diagnostic tools that provides clues as to digestive and overall health. However, it needs to be considered in addition to other information so that the clinician has a complete clinical portrait of the patient.

16.6.3 Sample Collection

Encourage that the client observe the patient defecating so that they can disclose the following details [12, 19]:

  • patient’s elimination site

    • normal/as expected
    • abnormal, as in house‐soiling (see Figure 16.9)

  • patient’s elimination behavior

    • normal/as expected
    • abnormal, as in new or unusual circling or nonproductive squats

  • patient’s posture during defecation

  • patient’s demeanor

    • normal and relaxed
    • abnormal and sense of urgency

  • vocalization during defecation
  • ease of defecation

    • normal
    • multiple attempts to produce stool
    • dyschezia
    • tenesmus (see Figure 16.11)

  • anatomy of the perineum

    • normal
    • abnormal (e.g. redness, swelling, fistulation and/or abscessation, discharge)

  • patient’s interest in perineum

    • normal
    • abnormal (e.g. licking, grooming, chewing, and/or biting excessively).

If the patient appears to be exhibiting tenesmus, are they straining to defecate or are they actually straining to urinate?

Feline posture for urination is often distinct from feline posture for defecation; however, not all clients are familiar with elimination postures in cats since cats tend to eliminate in privacy without spectators (see Figures 16.12 and 16.13).

It is helpful when the client witnessed the act of defecation especially in multi‐pet households so that you know the sample is truly associated with the patient in question [1, 19]. Sometimes owners will present a fecal sample that they gathered from the yard or litterbox. It may be grossly abnormal in appearance and/or microscopically, yet if more than one patient has access to the yard or litterbox, then it becomes a diagnostic challenge to know who the sample belongs to. If the fecal sample were to turn up positive in any regard [e.g. (+) for parasitism, (+) for blood, (+) for excessive mucus], then who do we treat and how? Diagnostic next steps are significantly more challenging when we must investigate everyone in the household.

16.6.4 Sample Collection Containers

Provide owners with a sterile collection cup and lid in advance of their next visit. This encourages compliance by training owners to bring in a fecal sample.

However, sometimes clients find themselves unexpectedly needing to sample fecal matter at home. In this case, they may reach for any container that is handy, including those that once housed food, detergent, or other residues. Instruct owners who find themselves in this position to use clean storage containers. The author has had fecal samples submitted to her in jam and jelly jars, many of which were not cleaned prior to filling. This impeded accurate observations about that sample’s physical properties because it was impossible to determine if the fecal matter was truly gelatinous or if that texture was the result of feces being added to a jar that contained jelly.

It is also important to note to members of the veterinary team that gloves should not be used as primary storage “containers” for fecal samples. When clinicians perform rectal examinations, they often extract feces in the process. It may be tempting for the clinician to invert the glove upon the gloved finger’s exit from the rectum, tie a knot in the glove, and consider that to be an appropriate sample holder. Although this is convenient for the clinician, feces stored within an inverted glove make a mess for the individual who must analyze the sample.

Snapshot of assessing feline BCS using the Purina 9-point system.

Figure 16.8 Assessing feline BCS using the Purina 9‐point system.

Source: Courtesy of Nestlé–Purina PetCare.

Photo depicts an example of house-soiling in a dog with diarrhea.

Figure 16.9 Example of house‐soiling in a dog with diarrhea. The patient demonstrated urgency to defecate but did not make it outside in time to release its bowels. This patient was subsequently diagnosed with colitis.

Source: Courtesy of Frank Isom, DVM.

Photo depicts normal canine posture for defecation.

Figure 16.10 Normal canine posture for defecation.

Source: Courtesy of Lisa Hallam, BS, CVT.

Photo depicts tenesmus in a dog with hematochezia.

Figure 16.11 Tenesmus in a dog with hematochezia.

Source: Courtesy of Danelle Capobianco.

Photo depicts normal feline posture for urination.

Figure 16.12 Normal posture for urination in a female cat.

Source: Courtesy of Ryane E. Englar, DVM, DABVP (Canine and Feline Practice).

16.6.5 Sample Size

Clients should be instructed on how much of a sample is needed to perform fecal analysis. On one hand, clients may be reluctant to bring in a sample for fear that they do not have “enough.” At the other extreme are those clients who may run out of space within their collection container to stow an entire log of feces.

Giving clients a visual with regard to size streamlines the sample submission process. Most in‐house fecal diagnostic tests can be run with 2–5 g of feces. For reference, one Hershey’s Kiss weighs roughly 4.6 g. This amount is less than the size of an adult’s thumb and is roughly the size of a quarter’s surface.

Photo depicts normal feline posture for defecation.

Figure 16.13 Normal feline posture for defecation.

Source: Courtesy of Ryane E. Englar, DVM, DABVP (Canine and Feline Practice).

Note that most fecal loops only extract, on average, 0.5 g of feces; therefore, unless this sample is being augmented by another source, it will not be sufficient for fecal flotation.

16.6.6 Age of Sample

  • Prolonged storage of feces will age the sample. As fecal samples age, they desiccate. This will artificially change the sample’s fecal score. You may inadvertently assign a low fecal score (if using the Nestlé–Purina scale) to a sample, implying that it is too dry when in fact it may have had an appropriate moisture content at time of collection.
  • Similarly, sample color may change over time. Aged feces do not retain the classic brown color that is associated with healthy digestion. Instead, aged feces discolor to gray, gray‐white, or even white. This process is hastened if samples are gathered from an enclosed yard in which fecal matter is exposed to intense sunlight. Sunlight will break down the normal pigments in stool. Humid environments may also trigger mold growth that discolors feces.
  • Aged feces may harbor maggots, that is, fly larvae [19] (see Figure 16.1). These are not parasitic. They do not reside within the digestive tract of canine or feline patients. They develop from hatching eggs that were laid on the feces by free‐living adult flies [19]. Some species of flies do not deposit eggs on feces; they deposit larvae directly [19]. These include flesh flies of the genus, Sarcophaga [19].
  • Prolonged storage of feces is also likely to potentiate false negative results during fecal analysis. That is, no ova or parasites may be seen. Identification of parasites microscopically (see Chapter 17) is often based upon their distinctive movement [19]. Parasites that would have been present and motile in fresh fecal samples may become immotile and/or they may die as feces age [19].
  • Finally, prolonged storage of feces may also complicate microscopic diagnosis (see Chapter 17) in that parasites rapidly develop through their various life stages [19]. In other words, parasite eggs do not remain eggs forever. They will hatch into larvae [19]. When they do, eggs will no longer be present in the sample.

16.7 Interpreting Test Results

16.7.1 Fecal Consistency

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May 3, 2023 | Posted by in SMALL ANIMAL | Comments Off on Assessing the Physical Properties of Fecal Matter

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