Further Reading
1 Byrne BA. 2007. Laboratory diagnosis of bacterial infections. In: Sellon DC, Long MT (eds). Equine Infectious Diseases. St Louis, MI: Saunders Elsevier, pp. 236–44.
2 Ferris RA, Dern K, Veir JK, Hawley JR, Lappin MR, McCue PM. 2013. Development of a broad‐range quantitative polymerase chain reaction assay to detect and identify fungal DNA in equine endometrial samples. Am J Vet Res 74: 161–5.
3 Ferris RA, Veir JK, Lappin MR, McCue PM. 2010. Development and clinical application of a broad range 16S quantitative PCR assay for detection of bacteria in the uterus of the mare. Anim Reprod Sci 121: S98–S100.
17 Uterine Cytology Collection: Swab/Brush
J. Dascanio1 and Ryan A. Ferris2
1 School of Veterinary Medicine, Texas Tech University, USA
2 Summit, Equine, USA
Introduction
A cytologic examination of the uterus should always be performed in conjunction with a uterine culture. Cytologic evaluation of the uterus involves the collection and interpretation of cells lining the uterus (endometrium) and within the uterine lumen. Endometrial cytology is a rapid, inexpensive technique to detect the presence of endometritis in the mare.
There are circumstances whereby a uterine cytology may be normal (no inflammatory cells) and an infection is still present. These include isolated infections, deep‐seated infections, or infections early in their course. It is also more common to have a negative cytology (i.e., no inflammatory cells) in the presence of an Escherichia coli infection than in the presence of a Streptococcus equi subspecies zooepidemicus infection.
Typically a guarded swab or a brush is used to obtain a uterine cytology sample; collection of a uterine sample with unguarded swabs may result in significant contamination from the vestibule, vagina, and cervix. A low volume uterine lavage may be more diagnostic than swab or brush samples in situations where isolated infections are present (see Chapter 18).
Equipment and Supplies
Tail wrap, tail rope, non‐irritant soap, roll cotton, stainless steel bucket, disposable liner for bucket, paper towels, sterile lubricant, sterile sleeve, guarded culture device (Kalayjian swab, single‐guarded; McCullough swab, double‐guarded or uterine brush), microscope slides, modified Wright’s stain (Diff‐Quik® or equivalent), microscope.
Technique
Remove feces from the rectum.
Place a tail wrap and tie the tail out of the way (see Chapter 4).
Clean and dry the perineum of the mare (see Chapter 3).
Place a sterile sleeve on the arm.
Place the guarded culture device into the palm of the hand.
Place sterile lubricant on the knuckles and down the length of the sleeve being careful not to get lubricant onto the palm. If the culture device becomes inundated with lubricant, it may be more difficult to obtain a diagnostic sample.
Rub lubricant from the knuckles onto the vulva, straighten the fingers and insert through the vulva, staying dorsal so as to not rub across the clitoris.
Using a slight rotating motion, pass the hand into the vagina so that the mid‐forearm is to about the level of the vulva. This should enable palpation of the external cervical os.
Gently insert the index finger into the external cervical os. Sometimes the os may be off‐center, located slightly downward, or to the left or right of center.
Pass the index finger through the cervix to the last knuckle (metacarpo‐phalangeal joint). Usually one can tell when the tip of the finger exits the internal cervical os and enters the uterine body lumen.
Insert the uterine swab/brush instrument along the inserted index finger through the cervix and into the uterine lumen. Sometimes, if the cervical canal is under the influence of progesterone and is toned, the index finger may need to be removed prior to passing the culture device. Typically, the instrument would be pointed in a slightly downward direction when being passed through the cervix due to the dependent nature of the suspended uterus within the abdomen.
The inner swab/brush is then advanced forward through the cap/guard.
Allow the swab/brush to be in contact with the endometrium and uterine secretions for 10–15 seconds and then reverse the procedure to remove the device.
Gentle rotation of the swab/brush may be indicated to pick up cells, but care should be taken to limit “heavy‐handed” movements of the uterine culture swab as this may predispose to breaking of the end of the swab or may be associated with mild hemorrhage and contamination of the swab with blood.
Once the culture instrument has been withdrawn from the external cervical os, a cupped hand should be placed over the device to limit vaginal cellular contamination to the swab/brush.
If a single swab was used, the swab should be gently rolled over a sterile microscope slide (and can then still be used for uterine culture). If a sterile slide is not available, then a second swab may be used to obtain a uterine culture.
If a single brush is used, a swab of the brush may be made for culture and then the brush rolled gently over a microscope slide. If the material discharged is thick, a second slide is placed over the first and gently pulled apart to create a smear.
It is also common practice to collect two samples from a mare; first a swab for microbial culture and then a brush sample for endometrial cytology.
Two slides are prepared from every sample in the event that one is broken prior to evaluation or if more than one stain is to be used.
Microscope slides should be air‐dried and may be fixed to preserve cellular architecture. The slides may then be stained with a modified Wright’s stain such as Diff‐Quik®.
Additional stains that may be considered are a Gram stain or a fungus‐specific stain such as Grocott methenamine silver (GMS) stain.
Interpretation
A cytology brush may yield significantly more cells than a swab for interpretation.
Distortion of cells may occur when a swab is rolled across a slide or during the collection of cells. This is more common if the swab is smeared instead of rolled across the slide.
Note any discharge present on the sterile sleeve when the gloved arm is pulled from the vagina. There should not be any purulent or hemorrhagic discharge, only the lubricant and clear mucus should be present.
Ensure that the culture device is intact and that no part of the instrument was left within the mare’s reproductive tract. Breakage of the swab/brush is more likely when the device is placed into a dependent uterus (older broodmare) and rotated, causing undue stress on the device tip.
Note any discharge on the tip of the culture device. It is not uncommon to see very mild hemorrhage on the culture device as it rubbed against the endometrium.
Microscopic examination is performed at 400× (10× eye piece and 40× objective) magnification for uterine endometrial cells (individual