Vaginal Cytology

Why is vaginal cytology performed?

To ensure fertility, detect STDs, detect cancer, and determine stage of estrous.

What type of swab is used to collect a vaginal cytology sample?

A saline-moistened swab.

How is the swab inserted into the vagina?

Through the vulvar lips, angled toward the clitoral fossa or dorsally toward the rectum.

What tools may help guide the swab?

An otoscope or vaginal speculum.

What happens if the swab is inserted too shallow?

The wrong type of cells will be collected.

What happens if the swab is inserted too ventral?

You may enter the bladder.

How is the swab applied to the slide?

Rolled/rotated several times onto a clean glass slide.

How are slides dried before staining?

Air-dried.

What stain is used for vaginal cytology?

Diff-Quik stain.

How does Diff-Quik use compare to hematology slides?

It requires more dips.

How is the slide examined?

Read under low power first, then high power to evaluate morphology.

What does exfoliative vaginal cytology help determine?

Stage of estrous cycle and optimal timing for mating or artificial insemination.

Should cytology be interpreted alone?

No, it must be interpreted with history and clinical signs.

How often are samples typically repeated?

Every few days.

What is a cornified cell?

A cell that lacks a nucleus.

What is a non-cornified cell?

A living cell containing a nucleus and organelles.

What is a keratinized epithelial cell?

Dead outermost layer; protective.

What is a non-keratinized epithelial cell?

Living cells with a nucleus; flexible.

What causes the vaginal wall to thicken?

Rising estrogen levels.

What happens as superficial cells move away from blood supply?

They detach (exfoliate).

How do exfoliated cells appear?

As flat scales.

Which cells are closest to blood supply?

Basal cells.

What happens to exfoliated cells as estrus approaches?

They become cornified.

What type of cells are exfoliated during estrus?

Cornified or squamous cells — completely keratinized with minimal/no nucleus.

What are parabasal cells?

Cells exfoliated during anestrus and early proestrus; lack keratinization.

What are intermediate cells?

Parabasal cells further along in keratinization.

What are partially cornified cells?

Cells becoming angular and more keratinized due to ↑ estrogen.

What are cornified/squamous cells?

Completely keratinized cells present during estrus; blue stain; little to no nucleus.

How are squamous epithelial cells classified?

By size and degree of cornification.

What other elements may be present on a smear?

Neutrophils, erythrocytes, bacteria (normal flora).

What are the characteristics of parabasal cells?

Smallest cells, round, large distinct nucleus, uniform in size/shape.

When are parabasal cells common?

Diestrus and anestrus; sometimes early proestrus; absent during estrus.

How large are intermediate cells?

Diameter ~3× that of parabasal cells.

Describe intermediate cells.

Large vary in shape with large cytoplasm and a small, round nucleus.

When are intermediate cells common?

All stages except estrus.

What are superficial cells?

Largest vaginal smear cells; polygonal, flat, sometimes rolled.

What do superficial cell nuclei look like?

Absent or pyknotic (dying).

What are fully cornified cells?

Superficial cells with no nucleus.

When are superficial cells seen?

Not in anestrus; increase in proestrus; large numbers in estrus; decrease at onset of diestrus.

When are erythrocytes common?

Proestrus (large numbers).

When are neutrophils common?

Early diestrus; rare during estrus.

Do neutrophils alone indicate vaginitis?

No.

What are foam cells?

Epithelial cells with vacuoles, seen in anestrus.

When are bacteria most abundant?

Estrus — normal flora.

4 stages:

• Anestrus
• Proestrus
• Estrus
• Metestrus (Diestrus)

What are clinical signs of anestrus?

No vulvar swelling, no attraction to males.

What is typical duration of anestrus?

~4.5 months.

What does anestrus vaginal smear show?

Predominantly noncornified squamous epithelial cells (intermediate and parabasal), ± few neutrophils, no RBCs, ± bacteria.

What are clinical signs of proestrus?

Vulvar swelling, reddish-brown discharge, attracts but does not accept males.

How long does proestrus last?

4–13 days (avg 9).

What does early proestrus smear show?

High numbers of RBCs, parabasal cells, few neutrophils, large numbers of bacteria.

What changes occur in late proestrus smears?

RBCs decrease; intermediate → superficial cells; angular cells; pyknotic nuclei; fewer neutrophils; many bacteria.

Clinical signs of estrus?

Swollen vulva, pink/straw discharge, accepts males.

Duration of estrus?

4–13 days (avg 9).

What does an estrus smear show?

Mostly superficial/cornified cells (often without nucleus), small numbers of RBCs, no neutrophils.

What marks the end of estrus?

Decrease in RBCs and rapid increase in neutrophils.

Clinical signs of diestrus?

Decreased vulvar swelling, decreased discharge, no longer receptive.

Duration of diestrus?

2–3 months.

What does a diestrus smear show?

Transition from cornified → noncornified cells within 10 days; abundant debris; ↑ neutrophils (first 3 days) then ↓; RBCs absent.

Are anestrus and metestrus cytologically similar?

Yes — difficult to differentiate.

What does inflammation of vulva or uterus look like?

Pinkish-white discharge without vulvar swelling or signs of proestrus/estrus.

What does vaginitis/metritis smear show?

Noncornified squamous epithelial cells, massive neutrophils, and possible bacteri