INFLAMMATION, INFECTION, OR BOTH? ROOT CAUSES OF ENDOMETRITIS


may be used to define the endometrial inflammation: normal (no white blood cells [WBC] to rare WBC/100 epithelial cells [EC]), mild inflammation (1–2 WBC/100 EC), moderate inflammation (3–5 WBC/100 EC), and severe inflammation (>5 WBC/100 EC).32 Endometrial biopsy has traditionally been the gold standard of diag- nosis of endometritis.34–36 This allows assessment of the inflammatory cell character and distribution and sever- ity of inflammation. Endometrial biopsies can be useful for identifying chronic endometritis when traditional cytologic sampling fails to identify inflammation.34–36


5. Noninfectious vs. Infectious Endometritis


Noninfectious endometritis can occurwhen there is con- tamination (air or urine) that continues to inflame the endometrium or when inflammation from foaling or caustic agents does not resolve but does not contain an infectious component. Post-mating-induced endometri- tis is often noninfectious. Identification of infectious en- dometritis is best achieved with diagnostic tests that identify microbes, such as aerobic culture of uterine swab, lavage efflux, or endometrial biopsy.14,19 Aerobic culture of uterine biopsy is the most sensitive and spe- cific means of diagnosing infectious endometritis.31,34,39 Aerobic culture of low-volume lavage efflux and subjec- tive character of lavage fluid have been reported as also being sensitive for detecting microbial organisms that may be harder to detect (E. coli, fungal organisms).40 Polymerase chain reaction and next-generation sequenc- ing of uterine samples are also helpful for detecting diffi- cult infectious organisms, but these tests are less readily available.41 Disruption of biofilm, “activation” of latent infections, and biofilmassessment have been pro- posed as novel diagnostic tools to identify underlying infections and susceptibility to nonantimicrobial agents not identified with traditional methods.20,42–44 These methods employ infusions of either biofilm disruptors or inflammation-inducing agents that stimulate suspected latent bacteria to replicate and make them easier to identify and treat.20,42–44 Using currently available diagnostic tests, it is


essential to incorporate all available information to make an appropriate diagnosis. Assessment of medi- cal and reproductive history and evaluation of the mare’s reproductive tract in estrus and diestrus (to include transrectal evaluation, vaginal speculum ex- amination, and digital cervical evaluation) allow iden- tification of anatomic findings that may contribute to subfertility. Intrauterine fluid, uterine edema, a cer- vix that fails to close, evidence of air in the vagina or uterus, and/or hyperemic vaginal mucosa during diestrus are not normal findings.19 During estrus, hy- peremia of mucosal surfaces, excessive endometrial edema, excessive intrauterine fluid accumulation >2 cmat any time (particularly if echogenic), and fail- ure of the cervix to dilate are abnormalities that war- rant further investigation.2,4,5,17 Culture and cytology


samples are often taken during estrus as there is a decreased chance of obtaining a false negative sample. Furthermore, the mare’s immune system is better prepared to respond to iatrogenic contamination intro- duced during sample taking. Moderate inflammation and any significant growth on aerobic culture of the endometrium suggests that the mare has endometri- tis and may require treatment. Hysteroscopy is used in cases of persistent endometritis despite appropriate treatment or when ultrasonography reveals signifi- cant abnormalities of the uterus (hyperechoic debris that persists, abnormal fluid accumulations).Once en- dometritis is diagnosed, the inciting cause must be identified in order to formulate an appropriate and successful treatment. History is again important as dystocia or unusual intrauterine treatments can often cause issues that must be addressed to abate the inflammation (cervical defects, uterine adhesions). Anatomic factors that cause chronic endometritis are important to identify and resolve as often without their resolution, no intrauterine treatment will be cu- rative. Failure of the vulva, vestibuo-vaginal fold, and/or cervix to protect the uterus from contamination must be addressed, most often surgically (Caslick’s, cervical repair). Recto-vaginal fistulas, urine pooling, and aspiration of air into the reproductive tract are not as common causes of contamination butmust also be ruled out in cases of chronic endometritis.Adhesions, diverticulae, scar tissue, and large cysts can form areas of debris and pathogen accumulation, which may alter normal uterine clearance mechanisms. Evaluation of the systemic health of the mare is equally essential as immune function and ability to resolve uterine infec- tionsmay be compromised by poor body condition, endo- crinopathy (pituitary pars intermedia dysfunction, equine metabolic syndrome), excessive body condition, pain, or stress.


6. Summary


Endometritis is a condition that involves both normal and abnormal progressive uterine responses to inflam- matory factors such as sperm, microbes, and debris. The challenge for the clinician is differentiating the abnormal uterine response and implementing appro- priate treatment. Careful evaluation of the mare, appropriate diagnostic tools, and interpretation of results can aid in identification of pathology and lead to appropriate treatment. Unfortunately, there is no single test with perfect sensitivity or specificity for identifying causes of endometritis. Therefore, practi- tionersmust rely on complete clinical evaluation of the mare to institute effective treatments. Fortunately, the majority of pathologic endometritis cases can be cor- rectly identified and easily diagnosed in routine brood- mare practice.


AAEP PROCEEDINGS / Vol. 68 / 2022 19


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