Hypothesis / aims of study
Urethral kinking, or mechanical obstruction secondary to urethral compression, which is associated with anterior compartment prolapse , has been suggested as an important risk factor for lower urinary tract symptoms .
Although some studies suggest the urethra may become kinked in cystocele with intact retrovesical angle, as a result of injury in ligamentous structures like pubo-urethral ligaments, the etiopathogenic mechanism is still unknown.
Pelvic floor ultrasound imaging has been demonstrated to be a useful tool to diagnose urethral kinking.
Even though kinking has been associated with voiding dysfunction, it is still not clear why some women with this condition do not have this dysfunction. In these field, there might be other urogenital symptoms that could have a stronger association with kinking and have not yet been studied.
The aim of the study was to evaluate the risk factors associated with urethral kinking, including epidemiological, ultrasound and clinical factors.
Study design, materials and methods
This is a retrospective study of 93 patients who were visited in a tertiary pelvic floor unit for a symptomatic anterior compartment prolapse (POP-Q STAGE ≥ II) from January 2018 to January 2019. All patients were assessed using anamnesis, validated ICS/IUGA questionnaires (ICIQ-SF, EPIQ), physical examination and translabial 4D- ultrasound.
We established 2 groups of study depending on urethral kinking finding in translabial pelvic floor ultrasound examination, diagnosed as cystocele with intact rectovesical angle, which results in a urethral compression against pubis as shown in Image 1.
Variables compared in both groups were: age, BMI, parity, maternal age at first birth, birth weight of the heaviest baby, previous history of instrumental delivery, prolapse severity (POPQ classification), and postvoid residual volume (including total and more than 50cc), levator ani avulsion muscle, ballooning of hiatus and urethral mobility by translabial ultrasound. Postvoid residual volumes were calculated according Dietz’s formula .
Once normality of variables was checked by Saphiro Wilk test, we performed a univariate analysis using a T-student test if the independent variable was quantitative and a Chi-square test if the independent variable was categorical.
We incorporated statistically significant variables in our univariate analysis in a multivariate analysis by logistic regression.
93 women were finally assessed, 52 patients (55,91%) had urethral kinking and 41 patients (44,09%) didn’t.
Epidemiological, clinical and ultrasound data of both groups are presented in Table 1-A.
In the univariate study, age, BMI, birth weight of the heaviest baby, levator ani avulsion, stage IV of POP-Q, total postvoid volume and postvoid residual volumes larger than 50cc were statistically significative when comparing both groups. However, after incorporating all these variables in a multivariate analysis, only total postvoid volume, postvoid volumes larger than 50cc and stage IV of POP-Q remained significative (p=0,0429 and p = 0,015).
Reported odds ratio of significant variables in multivariate analysis are presented in Table 2-A.
Interpretation of results
In our study Urethral kinking was associated with postvoid residual volume assessed by US, especially larger volumes. We also found an association between kinking and advanced anterior POP (stage IV).
We didn’t find epidemiological data or clinical data related to urethral kinking, including clinical postvoid dysfunction. The analysis of the ultrasound data did not show any levator injury, neither avulsion nor ballooning, associated with urethral kinking.
Our results suggest that urethral kinking could be a good indicator of ultrasound voiding dysfunction. However, in our study kinking was not associated with stress incontinence, overactive bladder or levator ani muscle avulsion but it was associated with advanced anterior POP. This last finding should be assessed in further investigation. Moreover, future studies are also needed in order to evalute how kinking and its clinical outcomes are affected after surgery correction.