Bladder endometriosis (BE) is present in approximately 1% of women with endometriosis (1), and it is defined as the presence of endometrial tissue in the detrusor muscle. An endometriotic lesion progresses from the serosal layer of the bladder towards the mucosa through the bladder wall. Dysuria has been reported in 21–69% in patients with BE (2). When an endometriotic nodule is observed in the bladder wall by transvaginal ultrasound (TVUS), a cystoscopy is usually performed to confirm the aetiology of the nodule and to estimate the distance between the ureteral orifices and the nodule borders. 
Our hypothesis is that TVUS could describe the degree of infiltration of BE and therefore, predict the results of the cystoscopy. Moreover, patients with more infiltrative nodules, affecting completely the detrusor, present higher prevalence of dysuria. 
The aim of the study is to compare the results of the TVUS and cystoscopy in women with BE.  Additionally, patients with less infiltrative nodules will be compared with those women with more infiltrative nodules.

A prospective study was designed, including patients with ultrasound diagnosis of BE who consecutively attended an Endometriosis Unit of a university tertiary referral centre, from January 2016 to December 2018. 
TVUS identified BE nodules and described the infiltration: nodules affecting anterior cul-de-sac and partially the detrusor were classified as less infiltrative nodules (Group 1), while more infiltrative nodules (affecting completely the detrusor with bladder protrusion) were classified as Group 2. Both ureteral meatus were tried to be identified in all cases. All TVUS were performed by two expert sonographers, using the endovaginal probe (RIC5-9, Voluson V730Expert, GE) for the pelvis and the convex probe (AB2-5, Voluson V730Expert, GE) for the kidneys (signs of hydronephrosis).  
After the sonographic diagnosis of BE, patients were invited to participate in the study, and informed consent were signed. Demographic and epidemiological variables, symptoms and previous surgeries were obtained: parity, infertility, haematuria and the prevalence and severity of symptoms (dysuria, dysmenorrhea, dyspareunia, pelvic pain, dyschezia) using the Visual Analog Pain Scale (VAS) from 0 to 10. 
A cystoscopy was performed in all patients by expert urologists, classifying the procedure in 2 categories: normal or endometriosic nodule affecting completely the detrusor with bladder protrusion. Concordance between TVUS and cystoscopy were analysed, considering that less infiltrative nodules (only partial detrusor) in TVUS would obtain a normal cystoscopy; while more infiltrative nodules (total detrusor) would be observed by cystoscopy.
Statistical analysis was carried out using SPSS v19.1. Quantitative variables were compared using Mann-Whitney U-test whereas qualitative variable were compared using Fisher exact test.

From 2016 to 2018, the two sonographers of the Endometriosis Unit performed TVUS to a total of 2207 women. BE was identified in 22 patients (1% of women), who were included in the study. The mean age was 35,8%±6.7 years old, only 2 were multiparas, 7 were infertile and 14 have had previous surgeries for endometriosis. 
Among the 22 nodules, 9 them affected only the anterior cul-de-sac and partially the bladder detrusor. These 9 women obtained normal cystoscopies (total concordance). TVUS detected 5 nodules that completely infiltrated the detrusor and protruded into the bladder cavity, and 8 nodules that additionally infiltrated the bladder mucosa. All 13 nodules were clearly visualized by cystoscopy (total concordance), although one of the nodule described as mucosa infiltrative by TVUS was described as normal mucosa by cystoscopy (5% discordance). Ureteral meatus were visualized up to 20/22 women by TVUS, while were identified and not obstructed by the endometriotic nodules in 21/22 women (5% discordance).  The mean of the major diameter of the nodules was 23.95±8.96 mm.
Considering symptoms, 14 patients reported dysuria (63%) and the mean severity of this symptom was 1±2.7 in Group 1 and 5.7±3.5 in Group 2 (p=0.0004). No statistically significant differences were found between groups in the rest of symptoms (globally, mean dysmenorrhea 7,60±2.4, dyschezia 3,05±3.7, pelvic pain 2,15±3.2 and dyspareunia 3,95±3.9). Only 4 patients reported haematuria, 3 of them with infiltrative nodules. 
Finally, only 4 women had signs of hydronephrosis in the abdominal ultrasound, all of them due to retrocervical nodules affecting ureters. BE did not cause hydronephrosis in any case.

The infiltration of endometriotic nodules in the bladder wall could be identified by TVUS, predicting the findings of the cystoscopy with high precision.
Nodules that partially affect the detrusor and do not protrude into the bladder cavity present normal cystoscopies, which should be avoided. 
Women with more infiltrative nodules referred more dysuria than women with nodules that not protrude in the bladder cavity.
Bladder nodules do not usually affect ureteral meatus and do not frequently cause hydronephrosis.

TVUS can diagnose the degree of infiltration of the endometriotic nodules in the bladder wall and the involvement of the ureteral meatus, with high accuracy in comparison with cystoscopy.  Cystoscopy should not be routinely performed in women with BE identified by TVUS.

Gabriel B, Nassif J, Trompoukis P, Barata S, Wattiez A. Prevalence and management of urinary tract endometriosis: a clinical case series. Urology 2011;78:1269–74.
Villa G, Mabrouk M, Guerrini M, et al. Relationship between site and size of bladder endometriotic nodules and severity of dysuria. J Minim Invasive Gynecol 2007;14:628–32.