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 there is a feeling of entering the uterine body lumen when the tip of the finger exits the internal cervical os.
Pass the uterine lavage catheter past the inserted index finger, past the internal cervical os, and into the caudal uterine body. 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 lavage catheter. Typically, the catheter 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 cuff on the uterine catheter should be inflated with approximately 75 ml of air to prevent reflux of fluid into the vagina. The cuff should be gently snugged against the internal cervical os.Figure 18.2 Infusion of sterile saline into the uterus by gravity flow for low volume lavage.
The 150–250 ml bag of 0.9% sodium chloride or other sterile fluid is elevated to allow the fluid to flow by gravity into the uterus (Figure 18.2).
The fluid is allowed to stay in the uterus for approximately 3 minutes to allow for distribution of fluid throughout the lumen.
In addition, the uterus may be gently massaged per rectum to ensure distribution of the fluid. Care should be taken to not irritate the endometrium with the lavage catheter.
The empty bag is subsequently lowered to allow a return of fluid via gravity flow (Figure 18.3). Gentle lifting of the uterus per rectum may increase return of fluid. If the fluid does not flow readily through the tubing, gentle aspiration with a catheter tipped 60 ml syringe may be used to initiate flow.
A single 20 IU dose of oxytocin may be administered intravenously to stimulate uterine contractions and augment return of the uterine fluid.
Once adequate fluid has been obtained, the clamp on the single‐line tubing is closed or the catheter is disconnected to make sure that there is no contamination of the recovered fluid with bacteria from the vaginal vault or caudal reproductive tract.Figure 18.3 Recovery of fluid from the uterus during a low volume lavage procedure.
The cuff is subsequently deflated and the catheter removed from the reproductive tract.
An alternative method involves passage of an insemination pipette into the uterus and the infusion of 60 ml of 0.9% sodium chloride via a syringe. The uterus is massaged to distribute the fluid and then the fluid is aspirated back into the syringe. Fluid recovery may be more difficult with this technique.
Recovered fluid is placed into one or two 50 ml centrifuge tube(s) and centrifuged at 400× g for 10 minutes. Alternatively, the cellular material may be allowed to settle by gravity for a few hours.
All but 5 ml of supernatant is removed and the pellet is re‐suspended in the 5 ml of lavage fluid.
Sterile culture swabs may be placed into the re‐suspended lavage fluid to obtain samples for cytology and culture. The culture swab is transferred to a transport media and the cytology swab is gently rolled across a microscope slide. The slide is air‐dried prior to staining with a modified Wright’s stain such as Diff‐Quik®.
An additional sample may be obtained from the centrifuge tube for polymerase chain reaction (PCR) analysis for bacterial or fungal DNA.
Interpretation
It is important that sufficient fluid is recovered from the uterus to be of diagnostic use.
Enough fluid should pass through the lavage tubing so that assessment of the uterine environment is performed. Care should be taken to not just pass fluid into and out of the catheter without actually contacting the uterus.
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 mucous should be present.
The clarity and presence of debris and mucus should be noted in the effluent fluid recovered from the uterus. Typically, the recovered fluid is graded as clear, cloudy, or cloudy with mucus.
Microscopic examination is performed at 400× (10× eye piece and 40× objective) magnification or under oil immersion at 1,000× (10× eye piece and 100× objective).
Evaluate slide quality (e.g., the presence of normal uterine epithelial cells) as well as the presence and relative number of inflammatory cells (neutrophils, macrophages, lymphocytes, etc.) and any bacterial or fungal organisms.
The amount of background debris and sediment appearing on stained slides from a low volume lavage is often greater than with swab or brush techniques. The amount of debris may be correlated with the degree of inflammation.
The presence of >5–10 neutrophils per high power field is an indication of inflammation, providing that an adequate cellular sample was obtained.
The greater the ratio of neutrophils : uterine epithelial cells, the greater the degree of inflammation or endometritis.
Neutrophils are the primary white blood cells present with acute inflammation. Macrophages, lymphocytes, and plasma cells may be noted with chronic inflammation. Eosinophils may be noted in cases of fungal endometritis, urine pooling, or aspiration of air into the uterus.
The absence of white blood cells (with normal endometrial cells present) often suggests that there is no inflammation present in the uterine lumen. However, some bacteria such as Escherichia coli and Pseudomonas aeruginosa may not stimulate a large inflammatory response and a “negative cytology” (i.e., the absence of white blood cells) may provide incorrect evidence of a “clean” or non‐infected uterus. Consequently, it is recommended that both culture and cytology samples be collected and evaluated and not just one or the other.
Please see Chapter 17 for further description of cell types found on cytology.
Further Reading
1 Ball BA, Shin SJ, Patten VH, Lein DH, Woods GL. 1988. Use of a low‐volume uterine flush for microbiologic and cytologic examination of the mare’s endometrium. Theriogenology 29: 1269–83.
2 Brook D. 1993. Uterine cytology. In: McKinnon AO, Voss JL (eds). Equine Reproduction. Philadelphia: Lea and Febiger, pp. 246–54.
3 Couto MS, Hughes JP. 1984. Technique and interpretation of cervical and endometrial cytology in the mare. J Eq Vet Sci 4: 265–73.
4 Leblanc MM, Magsig J, Stromberg AJ. 2007. Use of low‐volume uterine flush for diagnosing endometritis in chronically infertile mares. Theriogenology 68: 403–12.
19 Endometrial Biopsy
Patrick M. McCue