The phrase "urethral sphincter" refers to a muscular valve located in the urinary system. It helps control the flow of urine, allowing us to hold it in or release it when needed. Full definition
For example, if she was sound asleep, it might be due to a condition called urethral sphincter mechanism incompetence (USMI). (petsmagazine.com.sg)
Early gonad removal is commonly associated with urinary incontinence in female dogs and has been linked to increased incidence of urethral sphincter incontinence in males. (meisterhunde.com)
The poor success rate could be due to a variety of causes including a disease we call urethral sphincter mechanism incompetence (USMI - a urethra that does not have enough tone to keep the urine from leaking involuntarily). (vetmed.ucdavis.edu)