Discussion
A considerable proportion of patients with BPH ultimately undergo surgical treatment for BPH and, recently, laser prostatectomy has been increasingly selected 1, 2, 20. However, even though surgical treatment for BPH has been performed, a recent study reported that about a half of patients with BPH are still treated with medication due to the persistent LUTS6. In this regard, current clinical guidelines recommend a number of preoperative examinations 21. However, even though these examinations are performed, it is not easy to accurately predict the postoperative symptomatic improvement, and some novel parameters for predicting improvements in postoperative storage symptoms after laser surgery are needed due to the impairment of storage symptoms after laser prostatectomy as mentioned above. To the best of our knowledge, this is the first study to report the prevalence of decreased bladder compliance in patients with BPH who underwent laser prostatectomy and to evaluate the impact of bladder compliance on functional outcomes after laser prostatectomy.
In the previous study, the bladder compliance has been reported to decrease as men age 22, which is consistent with the findings of the current study. In that study, about 1 out of 5 patients showed decreased bladder compliance regardless of its severity, and about 1 out of 33 patients showed bladder compliance < 12.5 mL/cmH2O among patients with BPH who opted for laser surgery. In these men with bladder compliance <12.5 mL/cmH2O, preoperative subjective symptoms, especially storage symptoms, were impaired compared to men with bladder compliance > 25 mL/cmH2O. which is in accordance with previous study. These relations thought to be came from increased detrusor overactivity in men with poor bladder compliance23. Although decreased compliance could be related with the neurogenic bladder, in the current study, the prevalence of neurological or cerebrovascular diseases was not associated with bladder compliance, which might be due to the exclusion of patients with moderate to severe neurogenic bladders who were generally regarded as not optimal candidates for BPH surgery. In addition, in this study, bladder compliance was negatively associated with prostate volume or bladder outlet obstruction, in accordance with a previous study 24, 25. A previous study also suggested that BPH-induced decreased bladder compliance could be due to collagen deposition in the bladder smooth muscle fiber26.
The findings of the study suggest that as preoperative bladder compliance decreased, more improvements in storage symptom could be expected at long-term follow-up. However, interestingly, storage symptom was similarly improved regardless of the degree of bladder compliance at the short-term or mid-term follow-up, i.e., at 1 and 12 months postoperatively. Relief from of BPH seemed to be helpful for improving storage symptoms induced by decreased bladder compliance, although a few years are needed to realize these improvements, which was consistent with a previous study27. This could also be supported by another previous study demonstrating that restoration of bladder compliance was not significantly observed at 6 months after surgery 28. These findings might be related to the elimination of collagen deposition in the bladder smooth muscle fiber after resolving bladder outlet obstruction; however, this hypothesis needs to be validated in a future study. In addition, based on the results of the current study, clinicians could be more interested in the laser surgery for BPH in men with severe storage symptoms and decreased bladder compliance. However, because storage symptom was similarly improved regardless of the bladder compliance until 1 year, the clinicians should be careful for offering laser surgery in these patients with decreased bladder compliance by expecting immediate improvement in storage symptoms. In other words, clinicians should not avoid laser surgery in men with severe lower urinary symptoms because of the low bladder compliance, because storage symptoms might be alleviated with the time. One concern was that the effects of bladder compliance on functional outcomes might be not equivalent according to surgical methods. Based on the current study, HoLEP seemed to be superior compared to PVP regarding long-term voiding and storage symptom improvements, which might come from large removal of the prostate. However, the differences in storage sub-score outcomes according to surgical methods seemed to be minimized compared to voiding sub-score. In other words, compared to voiding sub-score, impacts of laser prostatectomy on long-term storage functional outcomes according to bladder compliance seemed to be similar regardless of surgical methods.
In addition, based on this study, bladder compliance < 12.5 mL/cmH2O was thought to be a reliable and reasonable cut-off value for predicting long-term functional outcomes after laser prostatectomy. This was because bladder compliance with 12.5–25 mL/cmH2O showed similar improvements for subjective symptoms compared to the bladder compliance ≥ 25 mL/cmH2O. Although several cut-off values for bladder compliance have been suggested17, 18, none of these cut-off values have been validated in patients with BPH who underwent laser prostatectomy. Furthermore, the results of the current study need to be validated in a future study with a larger number of patients and longer follow-up duration.
There were several limitations in the current study in addition to its retrospective design. Due to the long study period, the selection of the surgical methods may have changed, and this may affect the results of the current study. In addition, a relatively high drop-out rate through the long-term follow-up after surgery may have inadvertently created a selection bias. However, the results of the current study could be useful for clinicians to properly predict and explain surgical outcomes, especially in men with decreased bladder compliance.