To differentiate between stress incontinence and detrusor instability investigation done is -

Genuine stress incontinence is defined as urinary leakage occurring during increased bladder pressure when this is solely due to increased abdominal pressure and not due to increased true detrusor pressure. It is caused by sphincter weakness. Detrusor instability this is phasic increase in detrusor pressure (due to phasic contraction of detrusor muscle) giving rise to sensation of urgency of micturition and urge incontinence. It is found in pts with several types of neurogenic bladder dysfunction such as multiple sclerosis (MS) Parkinson disease or following a stroke or ceain types of spinal injury when it is known as detrusor hyperreflexia. Usefulness of Urodynamic testing: Distinguishing genuine stress incontinence from detrusor instability in women. Classification of neurogenic bladder dysfunction Distinguishing bladder outflow obstruction from idiopathic detrusor instability in men. Investigation of incontinence. Ref : Bailey & Love 25/e p1319