Factors Affecting Survival and Future Foaling Rates in Thoroughbred Mares with Hydrops

Prognosis for life and future fertility in broodmares following hydrops is reportedly good, but evidence to support these reports is limited. The objective of this case series was to describe the prognosis for survival and fertility in mares presented to a referral hospital following diagnosis of hydrops. Medical records were reviewed to identify mares diagnosed with hydrops. Data collected included history (gestation, sire of the foal), clinical findings at presentation and throughout hospitalization (complications, treatments, survival to discharge) and future foaling rates. Thirty mares were presented for hydrops between 2009 and 2019. Ninety percent (27/30) of mares survived (94.7% [18/19] hydrallantois, 75% [6/8] hydramnios) and 95% (20/21) of mares successfully had a future foal, of which 75% (15/21) had a foal the following year. There was no reoccurrence of hydrops. Mares managed with transcervical gradual fluid drainage demonstrated higher survival rate compared to those not managed with transcervical drainage (100% with vs. 78.6% without). The most frequent complications observed in mares that did not survive included hypovolemic shock (n = 7), hemorrhage (n = 4) and laminitis (n = 3). Complications observed in mares not returning to breeding included hypovolemic shock and hemorrhage. Causes of non-survival included peritonitis secondary to abdominal wall rupture or uterine tear, and tibial fracture. These results suggest that prognosis for survival and future fertility following a diagnosis of hydrops is good, provided the hydrops is diagnosed and treated appropriately with no damage to the reproductive tract or abdominal wall.