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Cytology in dogs and cats: indications and the course of the examination

Cytology in dogs and cats

On the skin of our pets, disturbing changes often appear - discoloration, hair loss, oozing wounds, pimples.

They often have problems with a runny nose or discharge from the conjunctival sac.

To cure your pet, you need to know what is causing the problem. One of the methods of diagnosing skin lesions (and not only) is cytology - a minimally invasive method, at the same time providing many answers.

In human medicine, it is mainly used for the prevention and early diagnosis of cervical cancers.

What exactly is cytology? When should you decide to have a Pap smear test?? What can be determined by a cytological examination?

I will try to present the topic of cytology in the article below.

  • What is cytology?
  • How to obtain material for a Pap smear?
  • Recovered material - and what's next?
    • What can be seen in Pap smear and when it is used?
  • Advantages and disadvantages of cytology
  • Risks and side effects

What is cytology?

Cytology involves taking a small amount of cells from an altered site, skin lesion, tumor, outflows or pustules, and transferring a thin layer of cells to a microscope slide.

The preparation obtained in this way is dried, fixed and stained (e.g. by Diff-Quick method or its derivatives) and evaluated by microscopic examination, initially under low magnification.

Disturbing areas of the specimen are then carefully assessed under higher magnification.

Pap smear should be performed by a physician experienced in the evaluation of preparations, or by sending the collected samples to a diagnostic laboratory.

The collection and proper fixation of the material is undoubtedly a success, however, improper assessment or ignorance of the appearance of cells in microscopic examination will make it difficult to diagnose the patient, and the examination will have no diagnostic value.

How to obtain material for a Pap smear?

Cells from the shift can be obtained in several different ways.

The impression preparation is obtained by pressing a slide placed over the skin lesion - it is the simplest method of obtaining a small amount of material for evaluation.

However, it works only in cases where the lesion is localized on the skin.

Cytology can also be performed before impressing the sample of an organ taken during the surgical intervention on the slide - cells from the top part of the cut will adhere to the slide, and after staining it will be possible to evaluate them.

The material can also be obtained by taking a swab with a swab or a brush.

This method is effective for lesions located in the animal's mouth or, for example, in the vagina.

The material obtained by fine-needle or coarse-needle biopsy (so-called tru-cut) allows the assessment of changes under the skin or in slightly deeper parts of the animal's body.

Cytology can also be made of sediment obtained from centrifuged urine or fluid collected from body cavities.

For cytological evaluation, it is worth taking the discharge from oozing wounds and pustules to check what exactly contains the lesion.

Recovered material - and what's next?

Pap smear

As I mentioned, after collecting the material, place it on a microscope slide and make a gentle smear.

It is important that the material is not placed in the form of a thick layer of cells, but a thin layer - conglomerates can make it difficult to correctly assess.

Often, several or a dozen slides are needed for proper assessment.

The smear should be dried and fixed.

The next step is staining - if the doctor undertakes cytological evaluation in the clinic, or securing the material and sending it to the laboratory.

What can be seen in Pap smear and when it is used?

Cytology is an important diagnostic tool. The image seen under the microscope depends on the type and location of the lesion from which the material was taken.

And so, in preparations for skin lesions, you can observe epithelial cells or deeper layers of the skin:

  • bacteria,
  • mushrooms,
  • hair,
  • skin parasites.

Crystals, epithelial cells, erythrocytes and leukocytes are sometimes visible in the urine sediment.

In the centrifuged fluid collected from the body cavities, fibrin, bacteria, erythrocytes and leukocytes can be observed.

In the material collected using the fine needle biopsy method, cells from the examined organ are visible. You can observe abnormalities in its structure - for example, neoplastic changes in cells, their deformation, fatty tissue of the organ.

In the case of vaginal cytology, the appearance of vaginal epithelial cells can be assessed. It is related to the oestrus cycle phase, on its basis the optimal mating or insemination date can be determined.

Cytological evaluation is used to determine the cause of skin lesions.

It is worth having a cytological assessment of the discharge from wounds, conjunctival sac or nose to see what may be its cause.

Cytology is performed when superficial lesions are suspected.

It is worth choosing this test in the case of recurrent inflammation of the bladder or diarrhea that do not respond to the antibiotics used (evaluation of the presence of Clostridium spores in a rectal swab).

As I mentioned, cytology is necessary in determining the stage of the oestrus cycle, and thus in determining the optimal fertilization date.

Advantages and disadvantages of cytology

Like any diagnostic method, cytology also has its advantages and disadvantages.

The undoubted advantage is the speed of diagnosis, if it is performed by an experienced doctor. The cytology assessment can be performed in several minutes to an hour.

It is irreplaceable in diagnosing skin lesions, helps in determining the etiology of changes - whether the infection is caused by bacteria, fungi or parasites.

Thanks to this, you can quickly implement effective treatment, or send material for further testing (for example, for bacteriological or mycological culture).

It is a fairly cheap test, its cost usually does not exceed PLN 150 - it sometimes depends on the number of microscope slides tested.

Usually, the patient does not need to be anesthetized to collect the material. Except for a few exceptional situations (for example in the case of a venous biopsy), the collection of the material is practically painless.

The disadvantage of cytology is the limited possibility of obtaining material in the diagnosis of lesions located in the deeper parts of the body.

When performing a biopsy of the parenchymal organs, the doctor must be very lucky to be able to get to a specific lesion, despite the ultrasound-guided biopsy.

In such cases, a better solution is a histopathological evaluation of an organ segment.

In the case of patients who are impatient with the collection of the material, the obtained sample may be insufficient for evaluation or not very representative.

The second disadvantage of cytology is the human factor.

Not every doctor is a specialist in the cytological assessment of changes, some changes are sometimes misdiagnosed, which delay the treatment process of patients.

A minor mistake during the staining of the preparation is enough, or the material spread too thickly on the slide for the cells to look completely different - this may also cause incorrect diagnosis of changes.

Risks and side effects

Cytology from the material obtained by a slide imprint or smear is a practically non-invasive method, so there is no need to prepare your pet for the test in a special way.

It has no side effects or risks.

A fine needle biopsy can be a bit unpleasant for an animal, but no more than an injection.

If the material is collected by biopsy, there is a risk of cancer cells being transferred to the so-called biopsy channel.

However, if the test result shows a neoplastic change, the site after inserting the needle is surgically removed anyway, so the risk of metastasis is negligible.

In order to obtain material by core-needle biopsy or organ removal, the animal must be prepared for anesthesia according to the recommendations of the attending physician.

Most often it is eight hours of fasting and blood tests before anesthesia, however preparation may vary depending on the patient's condition.

More than once, doctors hear from their caregivers "why move it ", "it's not worth doing research ", "why tire a dog or a cat ".

Diagnosing problems with the cytology method is not tiring for the animal or the owner's wallet, and it can provide an answer to the question of how to help the pet.

Do not be afraid to perform this test.

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