Stress urinary incontinence ( SUI ) is the most frequent involuntary urinary leak in women, constituting 10.7% of urinary complaints in urogynecology out patient clinics, being the cause of social, hygienic and psychic discomfort ¹.
The high indicator of therapeutic failure (15-30%) in the following five years of surgery are attributed mainly to an incorrect diagnosis ¹.
The urinary continence in women depends on the anatomical integrity of the bladder neck and proximal urethra, and the no damage of nervous fibres of these structures, keeping the bladder stable and the intra-urethral pressure superior to the vesical ².
Most of the authors agree that the lack of support in the vesical base, the bladder neck and the urethra, with enlargement of the mobility of the urethra to stress may cause SUI and the evaluation is important in the treatment of this nosological entity ^3,4,5,6.
The demonstration of the absence of an anatomical deficiency in patients with stress urinary incontinence and urgency, it is possible through the urodinamic study , visualizing the detrusor contraction during the filling of the bladder and the patients ability to inhibit this contraction when asked to do so ³ , while in instability of the detrusor we see an opening of the bladder neck with urinary voiding which the patient cannot inhibit ⁷ and in SUI we see a posterior rotation and a lowering of the bladder neck ( Fig 1A/B ).
For a correct diagnosis of the cause of urinary incontinence a history must be done, a physical and a gynecological exam, as well as a complementary propaedeutic that may include:

a) A urodinamic evaluation where the vesical filling and the voiding are analized, observing the presence of non inhibited contractions of the detrusor muscle, that characterize the vesical instability.

b) The Q tip test, that consists in the evaluation of the rotation deviation of the bladder neck backwards and downwards during physical effort.

c) Urethrocystometry that establishes a relation between the bladder neck and the pubic symphysis and evaluates the amplitude of the displacement of this structure of rest to effort, measuring the posterior urethrovesical angles and the urethral inclination.

d) Ultrasound, that is an alternative to the radiology methods, which may be associated to the urodinamic study.