Introduction
The diagnosis of bladder outlet obstruction (BOO) in women has become a challenge for Urology. There exist accepted nomograms for men such as the Abrams-Griffiths, the linpuRRR nomograms and the International Continence Society, any of these are applicable for women because the etiological factors for BOO are more diverse in females. The dynamics of voiding in females is more complex due to mobility of the bladder neck, proximal urethra and action of pelvic floor movements, whereas benign prostatic hyperplasia is the main cause in men. 
Normal voiding consists in a sustained and voluntary contraction of the detrusor muscle capable of evacuate the contents completely due of a coordinated and sustained relaxation of the external urethral sphincter and the entire pelvic floor.
Voiding symptoms like poor urinary stream hesitancy, straining and sense of incomplete emptying are suggestive of BOO, anyway a complete urodynamic evaluation must confirm it, other useful diagnostic studies are the ultrasonography in which the presence of residual urine volume higher than 150 cc is suggestive of BOO and cystoscopy which could determine the site of obstruction. 
Not only the absence of an etiology well identified, but also the lack of a universal agreement in urodynamics has resulted in the development of many definitions for BOO exclusively for women, plenty of definitions have taken place, yet it hasn’t been standardized 
Objectives:
The aim of our study is to compare the different definitions for BOO and find which one is most specific and sensitive in order to achieve a more accurate diagnosis

This retrospective study included the urodynamics and clinical data of 79 women already diagnosed with voiding disfunction. We categorized the women as obstructed or unobstructed based on Farrar, Chassagne, Lemack, Defreitas, Blavais and Groutz, Solomon-Greenwell definitions of BOO. The control group consisted of women who had been categorized as obstructed with at least 3 definitions of BOO. We then compared the control group with every definition of BOO and estimated the variance components with the Maximum Likelihood Positive Method (ML), P values were considered significant at <0.05.

From a total of 79 women, 50 were categorized as obstructed and 29 as unobstructed, the comparison between our control group and every definition of BOO has shown statistically significant difference. The Solomon-Greenwell nomogram has shown to be the more specific and sensitive, obtaining the highest likelihood positive ratio >100.

The urodynamic assessment of voiding provides critical data for workup and management for patients with BOO. Despite the urodynamics definitions of BOO having different cut-offs resulting in a pool of sensitivity and sensibility compared to one another, the Solomon-Greenwell nomogram has shown to be the most accurate definition.

To sum up, the diagnosis of BOO requires expertise and individualization, it is made through physical examination and complete urodynamic study.