Urethral plugs in dogs

Background: Crystalline-matrix urethral plugs have not been previously reported in dogs. Hypothesis/Objectives: To report the composition of urethral plugs in dogs, describe clinical features of the disease, and identify overrepresented breeds. Methods: Retrospective case series. A Minnesota Urolith Center (MUC) record search was performed for urethral plugs in dogs submitted during a 6-year period. The composition of the plugs and signalment of affected dogs were recorded. Breed risk analysis was performed using a control group without plugs from the Veterinary Medical Center, University of Minnesota (VMC UMN). Breed risk was also calculated for a group of dogs with struvite (plugs and uroliths). Medical records for the subset of plug cases from the VMC UMN were reviewed and described. Results: Between 2006 and 2011, 42 urethral plugs from dogs were submitted to the MUC. All came from male dogs, and the mineral component of the majority (83%) was struvite. Thirty (71%) samples were from Pugs. Pugs were overrepresented in plug submissions (OR 179; CI 88-389; P < .001), and for struvite in general (OR 14.3; CI 7.9-24.4; P < .001). Nine of the dogs were treated at VMC UMN; all were castrated male Pugs. None of these cases had bacteriuria or positive urine cultures, and no underlying cause of plug formation was identified. Conclusions and Clinical Importance: When evaluating dogs with urethral obstruction, plugs need to be considered, especially in male Pugs. Further investigation into the underlying cause of plug formation in dogs is warranted.