What is the typical signalment for a dog with urethral sphincter mechanism incompetence?

Urethral sphincter mechanism incompetence (USMI) is commonly observed in middle-aged, medium to large breed spayed female dogs. This condition arises due to the loss of tone in the urethral sphincter mechanism, often related to hormonal changes that occur after spaying. The risk of developing USMI is significantly higher in spayed females, particularly those that are middle-aged.

Spaying leads to a decrease in estrogen levels, which plays a crucial role in maintaining the integrity of the urethral sphincter. This is particularly evident in medium to large breeds where the anatomical structure and hormonal influences contribute to the susceptibility to this condition.

While younger dogs, senior dogs, and smaller breeds may experience other urinary issues, they are less likely to develop USMI specifically related to the loss of tonicity in the urethral sphincter as seen in the described demographic. Thus, the signalment accurately reflects the breed, age, sex, and reproductive status most commonly associated with this disorder.