Acquired urinary incontinence in the bitch: update and perspectives from human medicine. Part 2: The urethral component, pathophysiology and medical treatment.

Various pathologies can affect the bladder and/or urethral contractility causing signs of urinary incontinence. In this second part of a three-part review, the pathophysiology of impaired urethral contractility (including urethral hyper- and hypotonicity) in the bitch and in women is discussed. Urethral sphincter mechanism incompetence (USMI) is the most common form of acquired urinary incontinence in bitches and is characterized by a decreased urethral tone. The pathophysiology and current recommended medical treatment options for USMI and cases of modified urethral tonicity due to a neurological disorder or functional outlet obstruction are discussed. Treatment options in human medicine in cases of impaired urethral contractility are described.