IN-DEPTH INTERACTIVE: REPRODUCTIVE DISORDERS – PATHOLOGY TO TREATMENT


tools. However, it has been shown that uterine in- fections with E. coli and P. aeruginosa are not easily detected by positive cytology using traditional meth- ods. Therefore, the growth of one of these patho- gens warrants further investigation in the mare with a history of chronic subfertility. Procedures such as low-volume uterine lavage can be helpful in identifying infectious endometritis caused by gram- negative organisms.


Low-Volume Uterine Lavage


Low-volume uterine lavage can be performed to ob- tain a more representative sample of the uterine contents.10,19 It has been postulated that this method allows for sample collection from the entire uterine lumen rather than an isolated sample using an endometrial instrument (swab, brush, or biopsy). Low-volume lavage is best performed during di- estrus to allow complete dilation and exposure to recesses between endometrial folds. When the technique is performed during estrus, fluid tends to collect in between edematous endometrial folds and can be difficult to retrieve. After fecal evacuation and preparation of the per-


ineal area, a sterile Foley-type catheter is asepti- cally inserted through the cervix and into a uterine horn. Using transrectal guidance, the catheter is fed into the tip of one uterine horn. The catheter balloon is not inflated so that the catheter tip can be manipulated easily to aid in fluid evacuation. Ster- ile saline (150–250 mL), lactated Ringer’s solution (LRS), or phosphate-buffered saline are infused into the uterus. The fluid is agitated throughout the uterus using rectal massage for at least one minute. Oxytocin (10–12 IU) is administered intravenously to promote uterine contractility for fluid collection. Using transrectal manipulation, fluid is moved to the tip of the uterine horn where the catheter tip is placed. With the operator’s hand cradling the tip of the uterine horn around the catheter, the fluid is allowed to drain out through the catheter and back into the bag so that the system remains “closed.” Fluid is then transferred into conical 50-mL tubes. A minimum of 50 mL of efflux is needed for accu- rately representing uterine contents. Further- more, fluid should be processed for evaluation within 1 hour of collection to avoid iatrogenic cellu- lar changes.10 The clarity of the fluid is evaluated for mucus strands and cloudy contents that may indicate endometritis. In one study,20 cloudy and mucus effluxes were highly correlated with the pres- ence of microorganisms (E. coli and -hemolytic Streptococcus). The contents are allowed to settle for at least 1 hour, or the tubes are centrifuged immediately for 10 minutes at 400g. Determining g force on a standard benchtop centrifuge can be done with a nomograph and has been well de- scribed.21 After processing, fluid is decanted (if centrifuged) or aspirated (if allowed to settle), leav- ing 5 mL of supernatant and the pelleted cells. Two sterile cotton swabs are used to obtain samples


from the pellet. One sample is placed in transport media for bacterial culture; the second sample is smeared directly onto a slide for cytological evaluation. Low-volume uterine lavage provides a concen-


trated sample of cells and debris that can help identify subclinical infections. Results from low- volume uterine lavage should be interpreted cau- tiously; however, because the concentration process also increases the likelihood of isolating bacterial contaminants. It is best to interpret the samples from low-volume uterine lavage in conjunction with additional evidence of endometritis such as abnor- mal intraluminal fluid accumulation (especially in diestral or early estral mares), exuberant uterine edema, and repeated pregnancy losses after using good breeding management techniques. Positive indicators of subclinical uterine infection obtained from low-volume uterine lavage include cloudy or mucus fluid, isolation of known uterine pathogens, and more than onePMNidentified per high-powered field of concentrated cells. It is interesting to note that the cytological interpretation method recently reported by Kozdrowski et al.18 may be perfectly suited for evaluating samples from low-volume uter- ine lavage.


Endometrial Biopsy


Uterine tissue obtained through endometrial biopsy is considered to be the gold standard for detecting reproductive pathologies in the mare’s uterus.22 Microscopic examination of the endometrium pro- vides the most accurate means of identifying inflam- mation and other pathologies in the mare’s uterus. The endometrial biopsy should be taken at the base of one uterine horn, and a single sample has been shown to be representative of the entire uterus when considering inflammation or periglandular fibrosis. The sample should be submitted to a laboratory in an appropriate fixative (Bouin’s solution, Davidson’s solution, or 10% formalin) along with a detailed history of behavioral, ovarian, and uterine findings at the time of biopsy. Based on the degree of change in the characteristics that are described in the sections that follow, a grade is given with the modified Kenney scoring system.


Inflammatory Cells


Types, location, and distribution of inflammatory cells in the endometrial sample are noted. Neutro- phils often indicate acute inflammation, whereas lymphocytes indicate chronic changes. The pres- ence of a significant number of plasma cells is a poor prognostic sign because it indicates long-standing persistence of antigenic stimulus—usually bacteria. The presence of eosinophils indicates uterine irrita- tion such as urine pooling and/or pneumovagina. Treatment can resolve many types of inflammation.


AAEP PROCEEDINGS  Vol. 61  2015 279


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