Incidence of USMI after ovariectomy
Urinary incontinence is the involuntary loss of urine . In intact bitches urinary incontinence is rare (0-1 %) ,
whereas in spayed bitches the incidence is up to 20% .
The underlying pathophysiological mechanism is mainly an acquired insuffi cient closure of the urethra after spaying
. Therefore urinary incontinence after spaying is called urethral sphincter mechanism incompetence (USMI).
Within one year after spaying the urethral closure pressure is signifi cantly reduced. Because many bitches may only
become incontinent years after surgery it took a long time until the causal relationship between ovariectomy and the
occurrence of incontinence was proven . In one study, 83 of 412 (20%) bitches became incontinent 3 to 10 years after
As long as 40 years ago urinary incontinence was described as a rare side effect of spaying . However, it took 20
years to verify the causal relationship between the removal of the ovaries and urinary incontinence . The triggering
mechanism is still unclear.
Neuronal damage can most likely be disregarded, as the risk of urinary incontinence is the same in ovariectomised
and ovariohysterectomised bitches .