Diagnosis

Few mares presenting with signs and physical findings supporting a presumptive diagnosis of uterine tear have another lesion that could present in a similar manner. Affected mares typically are presented for evaluation up to 6 days after parturition, but the sooner a diagnosis of a uterine tear is made, the better the prognosis. The classic presentation is a mare that has depression, inappetence, colic, congested membranes, reduced frequency of borborygmus, and fever within the first few days after parturition. One fourth to one half of affected mares have gastric reflux.

Diagnosis by transrectal or transvaginal uterine palpation is complicated by the large size of the postpartum uterus in mares, which puts most uterine horn tears beyond reach (see Table 160-1). Also, pronounced postpartum endometrial folds can conceal small or partial-thickness tears. In large tears that develop secondary to uterine torsion, the foal can be palpated in the abdominal cavity directly through the rectal wall and more cranially in the abdomen than is usual. In such cases, the uterus can feel smaller than expected and highly toned.

Leukopenia is strongly associated with a diagnosis of uterine tear, although leukopenia can also be detected to a lesser extent in mares with metritis and postpartum disease of the cecum and small colon. Although mares with uterine tear associated with dystocia can have leukocytosis and neutrophilia with a left shift on the day of delivery, this is followed by marked leukopenia and neutropenia developing by day 3 after parturition and persisting to day 5. Circulating neutrophils frequently have toxic changes on cytology.

Abdominal ultrasonographic examination immediately after foaling may reveal no abnormal changes, but increased quantities of abdominal fluid with increased echogenicity and possibly fibrin tags are suggestive of peritonitis, and this can be confirmed by abdominocentesis. It is important to realize that normal parturition and even prolonged obstetrical manipulations do not change the peritoneal fluid profile from normal. A high value for a single peritoneal fluid analysis parameter can be considered as incidental, but two or more of the following could indicate severe postpartum disease: total protein concentration higher than 3.0 g/dL, total nucleated cell count higher than 15,000 cells/µL, and percentage of neutrophils higher than 80%. In mares with a uterine tear, peritonitis is exacerbated when uterine infusion is performed to remove a retained placenta and by fecal peritoneal contamination from foals that had fetal diarrhea during birth. Microbial culture of peritoneal fluid may yield no growth or polymicrobial growth, but monomicrobial growth is the most common culture result. Microorganisms isolated from peritoneal fluid can have a similar profile to the species of bacteria cultured from the uterus of postpartum mares. On cytologic examination, phagocytized bacteria, hemosiderin-laden macrophages, degenerated neutrophils, and extracellular bacteria can be seen.

In a small proportion of mares, uterine tears can be complicated by concurrent gastrointestinal lesions, such as large colon volvulus or evisceration (through the tear) of the large colon, small colon, or small intestine; hemorrhage from the vagina and uterine artery rupture are additional possible complications. Eviscerated intestine should be lavaged with warm sterile 0.9% saline and examined for mesenteric and vascular damage before it is returned to the abdomen, and abdominal surgery for resection and anastomosis may be necessary. Rare presentations that have been reported are a long-standing tear that caused a 16-month history of infertility as the sole clinical sign in one mare, and a partial-thickness tear that formed a small fluid-filled diverticulum covered by intact serosa in another mare.