Association Between Serum Total T4 Concentrations and Gallbladder Biliary Sludge in Dogswith Non-Thyroid Disorders: A Retrospective Case Control Study

Biliary sludge (BS) is a collection of solid particles that have settled out of bile.It is composed of precipitated crystals, glycoproteins, calcium salts, cellular debris and mucins.It can cause complications like biliary colic, acute cholecystitis, and acute pancreatitis.Hypothyroidism has been linked to BS formation, but dogs with reduced serum total thyroxin (tT4) concentrations caused by non-thyroid diseases may be predisposed to BS formation.A retrospective study was planned to investigate BS stages and sludge scores in dogs with non-thyroid diseases and their association with serum tT4 concentrations.For this purpose, records of 68 dogs with non-thyroid diseases (45 dogs with BS and 23 without BS) from private owners were evaluated.Gravity-dependent biliary sludge (GBS), non-gravity dependent biliary sludge (NGBS), gallbladder mucocele (GBM), sludge score, serum concentrations of tT4 and bile acids were recorded in all dogs.Results showed that BS was present in 66.18% of the dogs, with GBS being the most common stage (84.44%), and 60.53% of GBS dogs had sludge score 1.The BS group had significantly lower mean serum tT4 (P<0.05) and higher mean bile acid concentrations (P<0.01)than the non-BS group.The proportion of dogs with lower tT4 and higher bile acid concentrations was higher in the BS group (65.9 and 37.8%, respectively) and was significantly associated with the presence of BS (tT4: P<0.05, OR=3.3; bile acid: P<0.05, OR=6.0).In conclusion, BS formation was prevalent with an over-representation of GBS score 1 in dogs with non-thyroid diseases.As seen in primary hypothyroidism, dogs with lower serum tT4 concentrations due to non-thyroid diseases and higher bile acid concentrations would be predisposed to BS formation.