Overactive bladder syndrome in nulliparous women

Overactive bladder (OAB) syndrome, a multifactorial and nonspecific storage symptom complex with poorly defined pathophysiology, is characterized by urinary urgency, usually accompanied by increased daytime frequency and nocturia, with or without urgency urinary incontinence (UUI), in the absence of urinary tract infection (UTI) or other obvious pathological condition.^1–4 The International Continence Society (ICS) further recommended that these symptoms are usually “suggestive of urodynamically demonstrable detrusor overactivity (DO), but can be due to other forms of urethra-vesical dysfunction, and all of which can be named as lower urinary tract symptoms (LUTS).³ OAB may significantly affect quality of life, since there are a handful of studies showing the negative impact of OAB, such as increased health care visits, disturbance of sleep, higher rates of depression and anxiety, increased risk of fall-related injuries, increased risk of UTI, and of most important, reduced work productivity.⁵ Nonmodifiable risk factors and contributory factors for OAB in women include age, metabolic syndrome, post menopause, and pelvic organ prolapse (POP).^2,6,7 The possibility of OAB in young women without history of delivery (nulliparous [NP] women) is often neglected, resulting in underestimation of prevalence or incidence rate of OAB in the young population. Therefore, only few studies have attempted to investigate the impact of OAB on these young women, and many of them focused on the association of female sexual function.⁸ We are happy to introduce the current article from the Taipei Medical University Hospital to focus on the topic addressing OAB in NP women.⁹

The authors retrospectively enrolled 906 women with OAB, which were further separated into three groups as 221 NP, 571 parous women via normal spontaneous vaginal delivery (NSD), and 114 parous women via cesarean section delivery (C/S) to compare the urodynamic changes among three groups via urodynamic study (UDS).⁹ The NP had statistically higher rates of DO and female voiding dysfunction, including decreased peak flow and decreased mean flow, compared with NSD or C/S did.⁹ As expected, the NP were younger, and had higher maximum urethral closure pressure (MUCP) and longer functional urethral length (FUL) than NSD or C/S did.⁹ The current article is interesting and worthy of discussion.

First, as recommendation by the Urogynecology Section of the Polish Society of Gynecologists and Obstetrics guidelines on the management of non-neurogenic OAB in women, although the detailed diagnostic process is necessary to confirm the diagnosis of OAB before treatment, a UDS is not necessary during the initial assessment and is not the essential condition to initiate treatment.¹⁰ The diagnostic process and evaluation selection can be tailored to the individual needs and symptoms of the patients.¹⁰ Since the authors had performed UDS to evaluate subjects of OAB, it is supposed that these women may have other symptoms out of OAB or the physicians may consider the presence of other comorbidity of OAB. All were associated with a high possibility of the selection bias. In fact, this selection bias can be easily identified by significant difference of age among three groups in their study.⁹

In terms of UDS parameters in the current Fang et al’s study⁹ and based on the order of data presented in NP, NSD, and C/S groups, mean peak flow was 18.9, 21.4, 20.7 mL/s; mean flow was 7.5, 9.4, and 9.0 mL/s; mean MUCP was 104.9, 77.9, and 86.4 cm H₂O; mean FUL was 31.0 24.5, and 27.1 mm; and mean maximum cystometric capacity (MCC) was 339, 345, and 325 mL, respectively.⁹ Compared with previous OAB Taiwanese women reported by Dr. Hsu et al,¹¹ who has shown below that mean peak flow was 17.9 mL/s; mean MUCP was 73.4 cm H₂O; mean FUL was 26.5 mm; and mean MCC was 333 mL,¹¹ the certain degree of difference may exist, if statistical analysis was performed. However, both data were significantly lower than that obtained from the healthy women (23.5 mL/s for mean peak flow and 13 mL/s for mean flow as an example).¹² In fact, Dr. Hsu et al¹¹ further separated their OAB patients into the absence and presence of DO, and found the statistically significant difference of certain-type UDS parameters between two groups, including residual urine and peak flow rate.¹¹ Even though Dr. Hsu et al¹¹ tried their effort to distinguish OAB from interstitial cystitis,¹¹ since the latter should be managed by different strategies, such as an intravesical hyaluronic acid therapy,^13,14 the statistically significant difference was dramatically varied greatly when OAB women if these women were further separated into the absence of presence of DO.¹¹ Some are different and others are similar. Of most importance, the consistency is not always reproducible. All hinted us if we cannot clearly dissect the pathophysiology of OAB, it is difficult for us to manage these OAB women, even though the UDS procedure is applied.

As shown by authors, the authors hypothesized that NP may have hypertonicity or poor relaxation of the pelvic muscle, causing functional bladder outlet obstruction (BOO), which may be related to their OAB.⁹ It is reasonable. However, POP is a well-known cause of OAB symptoms in the affected women and BOO is a main reason of POP contributing to OAB symptoms. Based on the recommendation from the Polish Society of Gynecologists and Obstetricians guideline, the diagnosis of OAB should be made after excluding POP as the cause of OAB symptoms.¹⁰ In fact, Dr. Fang et al’s⁹ study showed the mean MUCP of NP with OAB was statistically significantly higher than that of both NSD and C/S with OAB, and also dramatically higher than that of normal volunteers (72-79.3 cm H₂O).¹⁵ Although the clinical meaning is uncertain for the aforementioned finding, it is worthy of further evaluation.

Finally, OAB is a bothersome disease, although it is not life-threatened and often underestimated, any effort to clarify its underlying pathophysiology and offer a better therapy is welcome. We hope to see more research articles addressing this topic in near future.

ACKNOWLEDGMENTS

This article was supported by grants from the Taiwan Ministry of Science and Technology, Executive Yuan, Taiwan (MOST 109-2314-B-075B-014-MY2 and MOST 109-2314-B-075-056), and Taipei Veterans General Hospital (V110C-082 and VGH109E-005-5).

The authors appreciate the support from Female Cancer Foundation, Taipei, Taiwan.