Introduction

Stress urinary incontinence (SUI) can occur following prostate surgery, whether for benign prostatic enlargement or prostate cancer if the underlying external urethral sphincter complex is damaged [1••, 2, 3]. The prevalence of prostatectomy incontinence (PPI) is more common in patients undergoing radical prostatectomy and published literature shows that innovations in robotic techniques and judicious adherence to pelvic floor physiotherapy can improve the continence outcomes in patients undergoing radical prostatectomy for prostate cancer [4, 5]. There is a consensus that progressive recovery of continence rates during the postoperative period can be expected up to 12 months with an estimated 10% of patients living with PPI in the long term [3, 6]. Although the presence of postoperatively de novo overactive bladder and urge incontinence is not common even without the addition of radiation therapy [7, 8], the question arises whether patients presenting with PPI should undergo formal urodynamics to exclude detrusor overactivity prior to continence surgery. While it is not established what duration of recovery time must be allowed to elapse to determine the final (irrecoverable) continence outcome, it is likely that the severity of PPI coupled with the presence of other equally important factors such as postoperative radiation therapy means spontaneous recovery of continence is less likely and there is a need to consider an earlier surgical intervention for persisting incontinence.

The AMS 800™ (Boston Scientific, previously the American Medical Systems, Minnetonka, MN, USA) artificial urinary sphincter (AUS) is widely acknowledged as the standard of care to treat males with moderate to severe stress urinary incontinence (SUI), following radiation-induced SUI and as a salvage option in those who failed male sling surgery [1••, 9•, 10•]. While it has been five decades since the landmark paper on the first modern AUS prototype was published [11], continued scientific advances in both device technology and surgical techniques have significantly improved its clinical efficacy, mechanical durability, and safety profile [12•, 13,14,15,16]. On the other hand, the modern synthetic male sling (MS) was developed in the early 2000s but has gained considerable recognition as an effective and less invasive surgical alternative to the AUS, and the patient is able to void spontaneously postoperatively [12•]. The modern MS can be categorized as an adjustable or non-adjustable sling. Despite the theoretical advantage of adjustable MS over non-adjustable MS with the ability to revise the sling tension in the event of persistent and/or recurrent incontinence, adjustable MS had higher complication and explant rates with each revision surgery [17, 18].

The most recent systematic review and network meta-analysis of various surgical treatments for PPI [19] showed that pooled overall odds ratios of patients achieving urinary continence compared with no treatment was 3.31 (95% credible interval, CrI: 0.749, 15.710) in AUS, 2.97 (95% CrI: 0.412, 16.000) in adjustable sling, and 2.33 (95% CrI: 0.559, 8.290) in nonadjustable sling based on 11 analyzed studies, with AUS ranked first in terms of continence rate, pad weight, and pad use count for under the cumulative ranking curve values of ranking probabilities for each treatment performance. Nonetheless, the unique noninferiority randomized MASTER trial reported that MS provides similar continence rates as an AUS (difference 3.6% [95% CI − 11.6 to 4.6, PNI = 0.003]) in terms of improvement in incontinence symptoms [20•] although post hoc secondary outcome measures analysis found the AMS 800 device to deliver superior clinical outcomes in terms of postoperative continence, overall satisfaction, and complication rates. Therefore, whether MS is indeed superior to AMS 800 device to treat PPI is a difficult question to answer (or prove) since both therapeutic devices are designed to treat different degrees of PPI. Equally, pertinent questions on whether urodynamics can assist or predict the success rate of MS or AUS in PPI, and if the sequence of continence surgery in relation to the timing of radiation therapy will alter the continence outcomes, require further research and critical discussion. This paper aims to evaluate the current evidence on the role of urodynamics in PPI and should MS or AUS surgery be performed before or after patients receiving radiation therapy in terms of continence outcomes.

Methods and Materials

Relevant English-published literature pertaining to PPI, MS, and AUS between January 1, 2000 and June 1, 2023 were undertaken and the following terms “artificial urinary sphincter,” “stress incontinence,” “postprostatectomy,” “male sling,” “recurrent incontinence,” and “complications” were searched in MEDLINE and EMBASE databases. The specific emphasis is placed on the task to address two important questions, namely: (1) Should urodynamics be performed prior to MS or AUS surgery?; (2) Should MS or AUS surgery be done in a patient prior to, or after salvage radiation for a biochemical recurrence?

Given there are very few prospective and almost non-existent randomized-controlled trials between MS and AUS surgery have been published, a full Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol was not adopted for this article; instead, a narrative approach was taken. A detailed analysis of all relevant studies including a full surgical description is not the goal of this paper although a brief discussion of the potential clinical challenges and surgical strategies to mitigate them will be provided in this narrative review.

Should Urodynamics be Performed Prior to MS or AUS Surgery?

Published international guidelines recommended that urodynamics may be performed to facilitate the diagnosis of incontinence and/or aid in patient counselling [1••, 7, 9•, 10•, 16]. Urodynamics provides a valuable diagnostic tool in determining the extent of true SUI in patients presenting with non-classic PPI or in a mixed urinary incontinence setting. Not all PPI is due to genuine SUI since de novo overactive bladder is estimated to occur in up to a third of male patients following radical prostatectomy [21, 22]. Furthermore, secondary detrusor overactivity can occur in patients who have poor preoperative bladder capacity or developed subsequent bladder outlet obstruction in the settings of bladder neck contracture or urethral stricture following surgery or radiation therapy [23,24,25]. For patients with non-classic SUI or mixed incontinence symptoms, urodynamics plays an important role in assessing underlying bladder (storage) dysfunction and detrusor contractility to exclude bladder outlet obstruction. Another study found that intrinsic sphincter deficiency (ISD) can be demonstrated in 54 patients (90%) out of 60 patients with PPI, although 27 patients (45%) patients were diagnosed with underlying bladder dysfunction and 16 (27%) of SUI cases were related to bladder dysfunction (rather than isolated ISD) [26].

The diagnosis of true ISD is based on the measurement of leak point pressure during the Valsalva manoeuvre (VLPP). The predictive value of VLPP in determining the success of MS has been reported in the literature, especially during the intraoperative setting of adjusting the optimal sling tension in adjustable MS cases [27,28,29]. However, it is important to note that a negative VLPP does not always exclude complete urinary continence since the measurement of VLPP in the presence of a urethral catheter may create some degree of urethral obstruction resulting in a false reading [30]. Hence, it has been recommended that VLPP should be repeated without a urethral catheter in situ [31, 32]. Furthermore, in some patients with severe PPI with complete sphincteric damage, it is not possible to fill the bladder to a sufficient volume to fully assess its storage pressures since it is not possible to achieve a steady state of filling, and use of foley catheter balloon or penile clamp may be necessary.

On the other hand, urodynamics-proven DO is thought to be quite common, especially in patients with mixed incontinence symptoms, and decreased bladder compliance can be observed in up to two-fifths of patients with PPI [33]. The presence of preoperative DO, bladder compliance, and capacity have been reported as adverse predictive factors in successful outcomes for male slings [34,35,36] and AUS outcomes [37, 38]. Adequate bladder contractility is a pre-requisite for MS since most MS cause some degree of urethral obstruction [39], whereas this would be less of a concern in the setting of an AUS where the circumferential urethral occlusion is released during micturition.

While the role of urodynamics can be useful in non-classic SUI or mixed incontinence symptoms with PPI, the more critical question to evaluate is whether the urodynamics findings will significantly alter the decision-making process in deciding whether to proceed with a continence surgery or not. These urodynamics parameters while not necessarily contraindicating a specific type of surgery, do provide useful information to counsel patients regarding postoperative expectations and the extent of continence (or voiding) outcomes. It is important to consider that many of these so-called de novo (or secondary) overactive bladder problems are often minor, may not be of clinical significance in the overall PPI presentation, and can be addressed effectively following continence surgery. Hence, international guidelines recommend the use of urodynamics in selected PPI cases such as those with a history of neurological disorder, pre-existing symptoms prior to postprostatectomy, or worsening incontinence following radiation therapy [1••, 9•, 10•, 40,41,42].

Should MS or AUS Surgery be Done in a Patient Prior to, or After Salvage Radiation for a Biochemical Recurrence?

Given that it is estimated around 10% of patients who underwent radical prostatectomy will end up with PPI at 12 months despite strict adherence to pelvic floor exercise therapy [3, 5, 6], and that radiation is shown to worsen PPI [1••, 6, 43], the question arises whether these PPI patients should undergo a continence surgery prior to radiation therapy or to wait and see if their incontinence rates get worse following radiation therapy.

Radiation can cause endarteritis and chronic vascular changes which invariably lead to decreased blood flow, thereby increasing the urethral tissue vulnerability and may result in higher complication rates; hence, it is generally agreed that patients who received radiation therapy constitute a group of high-risk patients with substantially higher risks of urethral stricture, atrophy, and device-related erosion [44,45,46]. The poor urethral tissue may also increase prosthetic-related infection risk [47, 48].

The rationales for proceeding with continence surgery in patients with PPI who will need salvage radiation therapy later include earlier restoration of continence and quality-of-life domains, potentially safeguarding against worsening SUI following radiation, and minimizing the theoretical risks of higher complication rates when operating in irradiated patients [49,50,51]. Furthermore, some of the patients with PPI may be able to choose from MS since it is considered a relatively contra-indication for radiated patients to receive MS due to lower continence outcomes and the perceived higher risk of sling erosion in irradiated urethra [52,53,54]. The hypothetical benefits for MS in PPI prior to radiation therapy are patients will be able to achieve continence and potentially safeguard this outcome with radiation therapy can “fix” the sling in place through radiation-induced tissue fibrosis [55].

On the other hand, given that radiation therapy may worsen PPI, perhaps it is best to wait until after salvage radiation therapy to determine the true extent of incontinence given the first continence surgery often offers the most effective therapeutic intervention. The decision to undertake surgery is likely dictated by patient preference and the urgency for salvage radiation therapy. Data pertaining to continence outcomes following AUS surgery in irradiated patients are mixed [49, 50, 56], although most literature shows that AUS patients with a prior history of radiation have higher rates of revisions given the higher rates of urethral erosion and atrophy [49, 57, 58]. The reasons for the poorer outcomes may be related to urethra atrophy or erosion [59, 60•] or perhaps secondary to other non-SUI lower urinary tract symptoms such as subsequent development of de-novo overactive bladder or (overflow) incontinence with stricture diseases which can occur over time [37, 51, 61]. The AUS is considered the superior option to salvage MS failure rather than a secondary MS surgery [9•, 10•, 62, 63]. Surgical strategies to manage recurrent incontinence in AUS patients with subsequent urethral atrophy include downsizing the cuff size, repositioning the cuff to a new urethral position, placing tandem (double) cuffs, increasing reservoir pressure, and performing transcorporal cuff placement or interposition of a biologic graft material between the cuff and urethra [60•, 64,65,66]. For irradiated patients, it is generally recommended that performing transcorporal cuff placement is a better and safer option to minimize the risk of cuff erosion in the fragile urethra [9•, 10•, 60•].

Conclusions

Both AUS and MS are effective surgical treatments for PPI. Urodynamics should be organized in non-classic SUI or mixed incontinence symptoms with PPI and those who had radiation therapy since it can provide useful information in counselling patients regarding continence outcomes and postoperative expectations. While the exact choice of MS or AUS, and the sequence of continence surgery in relation to salvage radiation therapy are debatable, irradiated patients are considered a high-risk group with substantially higher risks of postoperative complications. Hence, it is important to place greater emphasis on preoperative evaluation and surgical vigilance in irradiated patients with PPI.