Vaginal Smear for Oestrus Detection in the Bitch

()Map REPRODUCTIVE SYSTEM (Map) FEMALE REPRODUCTIVE TRACT VAGINA

Introduction

Vaginal smears can be used to determine the stage of the oestrous cycle. Smears are generally stained with Leishman's or a Trichrome stain such as Shorr's.

Vaginal Smears

• At the onset of pro-oestrus, large numbers of erythrocytes are present.
• When true oestrus occurs, the nuber of erythrocytes is reduced, and the smear consists of superficial cells from the stratified squamous epithelium. Such cells include:
  • Anuclear cells
  • Cells with pyknotic nuclei
  • Large intermediate cells
• Towards the end of oestrus, polymorphonuclear neutrophil leukocytes appear. These become the dominant cell type during metoestrus.
• In anoestrus,different cell types are present,these are:
  • Nucleated basal of the stratified squamous epithelium
  • Intermediate cells of the stratified squamous epithelium
  • Few neutrophils

Cell Type	Para Basal	Small Intermediate	Large Intermediate	Anuclear Keratinised	Red Blood	Neutrophils
Early Pro-Oestrus	+++	+++	+-	-	+	+
Late Pro-Oestrus	+	++	++	++	+++	-
Early Oestrus	-	-	+++	++++	++	-
Late Oestrus	-	-	+++	+++	-	+
Ealy Metoestrus	-	+	-	+-	-	+++
Anoestrus	++	+	-	-	+-	+
Vaginitis/Pyometra	+-	+-	+-	-	+-	++++

Vaginal Epithelium

• Anoestrous: low columnar-cuboidal, comprises of 2-3 layers.
• Pro-oestrus: high stratified squamous persists until late stages of oestrus.
• Stratum corneum and the layers immediately beneath it are lost by desquamation during pro-oestrus and oestrus. This leaves low squamous epithelium, which becomes converted to columnar epithelium 1-3 weeks after the end of oestrus.
• Metoestrus and pregnancy: high columnar, higher than during anoestrus.
• During pro-oestrus, oestrus and early metoestrus, the epithelium and lamina propria are infiltrated with large numbers of neutrophils, which eventually escape into the vaginal lumen.