Urgency is the sudden and intense desire to pass urine which is difficult to defer. It is often triggered by things like putting the key in the door, hearing the sound of running water etc.
Urge urinary incontinence is leakage of urine associated with this sudden urge. Not everyone that has urgency will have incontinence.
The most common cause of urgency is ‘overactive bladder’. The bladder itself is a muscle that is in relaxation mode to expand as it gradually fills with urine. As the bladder fills we should get a gradual build up in the desire to urinate relative to the amount of urine in the bladder. This allows us to voluntarily urinate when we need to. When we decide it is time to urinate the bladder muscle contracts and our pelvic floor relaxes which allows urine to come out. In ‘overactive bladder’ the bladder muscle spontaneously contracts at variable urine volumes. If the pelvic floor muscle is not strong enough to withstand the bladder contraction then leakage will occur.