Objectives To describe the electrophoretic pattern of proteinuria in dogs with naturally occurring Cushing's syndrome. We hypothesised that urine protein electrophoresis in dogs with spontaneous Cushing's syndrome will reveal glomerular proteinuria. We also hypothesised that the severity of proteinuria would decrease during treatment with trilostane. Materials And Methods This prospective study included dogs with spontaneous Cushing's syndrome (n = 19) and healthy dogs (n = 10) serving as controls for urine protein electrophoresis. Urinary proteins were evaluated using sodium dodecyl sulphate agarose gel electrophoresis. Results Thirteen dogs with Cushing's syndrome had glomerular proteinuria, with high molecular weight bands between 66 and 150 kDa. Three dogs with Cushing's syndrome had mixed glomerular and tubular proteinuria, with low molecular weight bands between 14.3 and 26 kDa, in addition to high molecular weight bands. Three dogs with Cushing's syndrome had a physiological pattern of urine protein electrophoresis and these dogs were non-proteinuric. Seven dogs were re-evaluated 4 to 6 months after initiating treatment with trilostane. Before treatment, six dogs were proteinuric and one dog was non-proteinuric. After the treatment, three dogs were non-proteinuric and four dogs were proteinuric. Of these, proteinuria decreased in one dog (50%) and increased (up to 70%) in three dogs. Clinical Significance Dogs with Cushing's syndrome predominantly exhibit glomerular proteinuria. No systematic improvement was observed during trilostane treatment.
