Cholelithiasis associated with recurrent colic in a Thoroughbred mare

A 13-year-old Thoroughbred mare, retired from race, was admitted to Equine Hospital, Korea Racing Association with signs of colic. One and a half months following the previous treatment (second time) and 11 days following her previous discharge (third time), the mare repeatedly exhibited signs of colic and finally along with icteric eyes. Routine medical treatment with intravenous fluids, analgesics resulted in resolution of signs of colic in the first and second admission. The condition of the mare did not improve in the third admission despite over one month supportive treatment and she was subject to euthanasia at the request of the owner on the thirtyeighth day of hospitalization (95 days from her first admission). The clinical signs (fever, icterus, mild intermittent colic) in conjunction with clinical laboratory findings (leukocytosis, elevations of serum total bilirubin, direct bilirubin, alkaline phosphatase, aspartate aminotransferase, gamma glutamyl transferase, creatine phosphokinase, lactic dehydrogenase and blood fibrinogen indicative of obstructive biliary disease) in this mare suggested possible chlolelithiasis. However, liver enzymes and bilirubin estimations are often not part of routine screening in emergency colic cases. At necropsy, multiple dark brown choleliths of various sizes obstructing hepatopancreatic ampulla were found in the hepatic duct. The choleliths were found as large as 3-5 cm in diameter, faceted to each other, dark brown in color and showed soap consistency. Histopathologic findings revealed: biliary fibrosis, plugging of the bile canaliculi with bile pigments, cholangiohepatitis and pigmentation of the hepatic lymph node with bile pigment laden macrophages. Although definitive diagnosis of cholelithiasis might be challenging, clinicians should consider this condition in the differential diagnosis of recurrent colic.