Texas Equine Veterinary Association

• 15 • Idiopathic low grade colic: Like other horses, pregnant and post-partum mares can develop a low grade colic (Slone, 1993). Changes in motility and location of the large colon because of the increasing size of the uterus may contribute to this type of colic. Another cause would be mild contraction of the uterus or fetal movement leading to discomfort in the mare (Steel & Gibson, 2001). During the examination of low-grade colic, special consideration should be taken to palpate the uterus to check for evidence of uterine torsion and the fetal tonus and movement, which would indicate fetal viability. Traditional treatment of mild colic signs includes analgesics such as flunixin meglumine and laxatives. If the mild colic signs persist, this could be indicative of a more serious issue. Large colon volvulus: In a longitudinal study, the incidence of postpartum colic in mares was 11% out of a given broodmare population (Weese et al., 2015). 36% of these mares were diagnosed with large colon volvulus which holds a high mortality rate (Driscoll et al., 2008). In another study, broodmares were 13 times more likely to develop large colon volvulus compared to their maiden counterparts (Suthers et al., 2013). Finally, one- fih of the surgeries performed within a 24-year period at an equine referral hospital were broodmares with large colon volvulus (Hackett et al., 2015). ese statistics indicate the importance of large colon volvulus in postpartum mares, an aspect that needs further research, including the change of the gastrointestinal microbiome over the equine pregnancy they may contribute to these postpartum colic cases. Large colon torsion: Large colon torsion is a more serious cause of colic in mares. It is the most common cause of surgical treatment in the pregnant mare (Boening & LEENDERTSE, 1993). e signalment of ~100 day postpartum mare is most commonly associated with this fatal form of colic (Hance et al., 1991). Clinical signs of large colon torsion include acute, violent colic with progressive abdominal distension. Gastric reflux is present in up to 35% of the cases. Signs can get as severe as shock with rising heart rate and deterioration, with pale mucous membranes if intestinal strangulation is present. Upon rectal exam, a severely gas distended large colon will be palpated. e diagnosis is based on severity of pain based on unresponsiveness to analgesia. e definitive diagnosis will be determined upon abdominal exploration. e survival rate is increased by early surgical intervention in these causes (Embertson et al., 1996). Large colon torsion recurrence is frequent with 15% of mares surviving the first episode relapsing (Hance et al., 1991). Urogenital tract-related colic: Urogenital tract colic is typically caused by arterial rupture and hemorrhage, which can affect up 3% of broodmares (Arnold et al., 2008). Small vessel tears are commonly related to the trauma associated with parturition. e small tears are likely contained within the peritoneal folds of the broad ligament (Offer et al., 2022). If major arteries are involved, such as the uterine or ovarian arteries, and if the bleeding continues, it can become painful causing tachycardia and anemia leading to shock, which presents as colic. Urogenital trauma is more common in aged multiparous mares (median age 13 years old). Anemia, hypoproteinemia, and hypofibrinogenemia are clinical findings associated with urogenital tract hemorrhage (Dolente et al., 2005). Leukopenia has also been associated with urogenital hemorrhage. e diagnosis of this disease is challenging because of the large size of the gravid or post gravid uterus. Definitive diagnosis can be made on palpation in certain mares (Dolente et al., 2005). Another diagnostic method is laparoscopy of the uterus and celiotomy. Another cause of urogenital tract colic is uterine tract tears. ese tears can be detrimental to the mare, eventually leading to septic peritonitis, the release of endotoxins and death. Mares present febrile, depressed, painful, with pale mucous membranes and bloody vaginal discharge. It is common for the mare to present days aer the injury occurred (Hooper et al., 1993). Cecal or colonic rupture: is form of colic is associated with parturition and can occur aer normal birth or dystocia (Dart et al., 1997; Rossdale, 1994). Aer the rupture, peritoneal contamination, severe peritonitis, profound endotoxemia, and death usually occur within 24 hours. is form of colic can be diagnosed by rectal palpation, abdominal ultrasound, and examination of the peritoneal fluid. e peritoneal fluid analysis reveals intestinal content and septic peritonitis. Euthanasia is oen necessary aer confirmation of this disease (Steel & Gibson, 2001). Rectal prolapse: Rectal prolapse is in general uncommon in horses. ere are four types of rectal prolapses recognized in the mare. Type I involves the mucosa or both the mucosa and the submucosa.

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