Introduction

The management for large prostate glands of more than 80 g in obstructive benign prostate hyperplasia (BPH) remains challenging [1]. Open simple prostatectomy (OSP) can still be considered to be the standard of care, if laser enucleation or vaporization is not available or institutionally standardized. However, the blunt dissection with the fingertip in the apical and sphincteral areas makes this procedure very invasive regarding perioperative and functional outcomes. Therefore, alternative approaches have been proposed, such as laser techniques, conventional laparoscopy and robotic-assisted simple prostatectomy (RASP).

Open simple prostatectomy (OSP)

Open Simple Prostatectomy (OSP) was first described in 1901. Freyer reported the first 4 cases in open transvesical technique, which is still used today by many urologists [2]. In 1949, Millin proposed the retropubic transcapsular approach [3]. In general, it is widely accepted that the risk of complications, i.e. severe bleeding, transfusion rate and prolonged hospital stay is quite significant. In a contemporary series with 1800 patients, an overall complication rate of 29%, severe bleeding in 12% with transfusion rate of 8% and sepsis in 9% was described [4]. OSP is still a common treatment even in developed areas for benign prostate enlargement with a range of up to 40% of all cases performed [1, 5,6,7] (Table 1).

Table 1 Open simple prostatectomy (OSP): published open series
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Conventional laparoscopy

Conventional Laparoscopic Simple Prostatectomy (LSP) in transperitoneal and extraperitoneal technique has been repeatedly evaluated since 2002 [8,9,10,11,12,13,14,15,16]. Functional results after LSP were found to be stable for 4 years, while thereafter Qmax decreased significantly [9]. So far, over 1200 cases of LSP have been published in the literature with the accepted benefits of less invasiveness and morbidity, i.e. reduced blood loss and transfusion rate, shorter hospitalization and very rare reoperations (Table 2). The biggest series in LSP so far was published by Zarraonandia et al. in 2019. They evaluated in 272 patients a median IPSS of 4 and Qmax of 23 ml/s after 3 months. However, due to longer learning curves and an increasing availability of laparoscopic robotic technology, LSP is not commonly distributed (Table 2).

Table 2 Laparoscopic simple prostatectomy (LSP): published laparoscopic transperitoneal and extraperitoneal series
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Laser technology

Although OSP has been the gold standard for a long time, a variety of minimally invasive treatment techniques—such us Holmium laser ablation and enucleation, KTP-laser prostatectomy and photosensitive vaporization—have been proposed to decrease invasiveness [17]. Enucleation and Ablation of the Prostate (EEP) mostly by Holmium laser (HoLEP) and Greenlight laser (GreenLEP) show excellent results with short catheterization time and hospitalization without significant blood loss [18]. The growing availability of different EEP procedures has reduced the number of OSP substantially [19].

History of robot-assisted simple prostatectomy

Feasibility of robot-assisted simple prostatectomy (RASP) was first reported by John et al. at the Annual AUA Convention 2007 as a video presentation [20]. Sotelo et al. [21] published the first transperitoneal RASP series one year later with 7 cases in 2008, while John et al. [22] reported 13 extraperitoneal RASP cases in 2009. In 2014, Stolzenburg confirmed the feasibility of extraperitoneal RASP in 10 cases [23].

RASP series show encouraging results with short hospital stay, and low blood loss and transfusion rates [21,22,23,24,25,26,27,28,29,30,31,32,33,34,35] (Table 3). Within 13 years after the first mention of RASP, a variety of modifications of RASP have been described.

Table 3 Robotic-assisted simple prostatectomy (RASP): overview
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Surgical techniques of robotic-assisted simple prostatectomy

Transperitoneal/extraperitoneal and transvesical/extravesical access

With all robotic platforms currently in use, RASP is technically feasible. Most teams prefer a transperitoneal access reflecting the experience with robotic radical prostatectomy. In general, a 4-arm robotic system is installed either transperitoneally or extraperitoneally. In the initially described techniques by Sotelo and John [21, 22], a transverse cystotomy was performed. Pokorny et al. proposed a vertical cystotomy after dropping the bladder beginning at the vesico-prostatic junction [30]. The bladder can also be left in place, attached to the abdominal wall at the dome region for approaching the adenoma. In their bladder neck sparing technique, Shahait et al. observed in a very recent study (2020) 42% of the patients with intact antegrade ejaculation [36].

Enucleation of the adenoma

Most centers ligate the dorsal venous complex to prevent back-bleeding during the enucleation, however, it is not always required.

In the transvesical approach, the incision of the mucosa is first performed at the dorsal edge of the adenoma and then continued circumferentially. If the ureteral orifices are close to the line of resection, they can be temporarily stented. The adenoma is developed by sharp and blunt dissection, starting dorsally. The adenoma can be maintained in toto or divided in both lateral lobes including middle lobe. The feasibility of single-port enucleation was evaluated by Desai 2010 and Fareed 2012 [37, 38]; however, the technology was not further standardized, and benefits for RASP were not obvious.

Apical dissection

The direct view within the prostatic fossa is a big advantage of RASP, allowing prostate capsule penetrating vessels to be coagulated under visual control (Figs. 1, 2, 3 and 4). The sphincter area remains efficiently protected, as the apical adenoma is released under visual control [39].

Fig. 1
figure 1

This figure is reprinted with permission from “Robotic Urology” (John H/Wiklund P, Eds), 3th edition, p 269, 2018

Transperitoneal transvesical approach, the dropping of the bladder is facultative, horizontal or vertical cystotomy showing both ureteral orifices. The tip of the transurethral catheter Ch20 marks the beginning of the prostatic urethra. ©KSW.

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Fig. 2
figure 2

This figure is reprinted with permission from “Robotic Urology” (John H/Wiklund P, Eds), 3th edition, p 269, 2018

Sharp and blunt dissection of the adenoma with fenestrated bipolar forceps and scissors. Both ureters can be stented facultatively if the orifices are close to the resection borders. ©KSW.

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Fig. 3
figure 3

This figure is reprinted with permission from “Robotic Urology” (John H/Wiklund P, Eds), 3th edition, p 269, 2018

The intraprostatic hemostasis is done under vision. As in open surgery, the fossa is then tamponated around the indwelling catheter Ch20, the balloon is gently blocked. ©KSW

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Fig. 4
figure 4

After removal of the adenoma, the control of bleeding from the prostate fossa can be performed under vision. The bladder neck and the trigone are drawn into the prostate fossa toperform a posterior vesico-urethral anastomosis which decreases the surface of the prostate fossa [40, 41]. ©KSW

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Reconstruction

Coelho et al. described in 2011 a plication of the posterior prostate capsule in a pilot series of 6 patients in transperitoneal transvesical technique with a continuous vesico-urethral anastomosis [26]. To decrease the size of the prostate fossa and control bleeding from the fossa, Castillo et al. [40] proposed in 2016 to plicate the prostatic capsule but to perform only a posterior vesico-urethral anastomosis, which was confirmed by Häcker and Thüroff [41]. Performing a total prostatic urethral sparing enucleation, Wang et al. reported preservation of the antegrade ejaculation [42].

Comparative studies

Multiple RASP series have been performed over the last 13 years. All of these series confirmed the technical feasibility, as well as efficiency and safety; furthermore, some technical modifications were described. However, despite big multicenter retrospective series [24], randomized prospective studies are missing. This is a common situation in surgical research, as operative teams usually focus on one technique that is developed and afterwards compared with the current standards. RASP has been compared with OSP, LSP and EEP in several trials.

Robotic-assisted versus open simple prostatectomy (RASP-OSP)

RASP versus OSP was studied by Sorokin et al. [43], Mourmouris et al. [44] and both Dotzauer et al. [45] and Hamann et al. [46] in 2020 (Table 4). In all trials, RASP showed significant advantages concerning hospital stay, blood loss and blood transfusion rate. Dotzauer described a lower complication rate in the RASP group (Dindo-Classification ≥ 2) and mentioned a very low urethral stricture rate after RASP. On the other hand, operative time is generally longer in the RASP group. Fewer complications and shorter hospital stays might offset the higher material and operative costs of RASP (Table 4).

Table 4 Robotic-assisted simple prostatectomy (RASP): comparative series with open simple prostatectomy (OSP), endoscopic enucleation (EEP) and laparoscopic simple prostatectomy (LSP)
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Robotic-assisted versus laparoscopic simple prostatectomy (RASP-LSP)

Since the first series from Mariano et al. 2002, LSP has become a viable option to transfer OSP to laparoscopy [8, 11] with the benefits of a less invasive technique, thus reducing blood loss, hospitalisation and complications (Table 2) Pavan et al. [47] compared 2016 in a multicenter retrospective analysis 130 RASP and 189 LSP patients and found no differences in blood loss, catheter and hospitalisation time and complications (Table 4). Martin Garzon confirmed these findings the same year with a smaller cohort [48].

After implementation of RASP in 2007, robotic-assisted technique gained in importance and surpassed standard laparoscopy. In particular, it is hardly possible to perform some of the intraprostatic reconstructive technical and anastomotic modifications with conventional laparoscopy [26, 40]. Today, LSP might still play a role in centers without access to robotic technology but a presence of laparoscopic expertise instead.

Robotic-assisted simple prostatectomy versus endoscopic enucleation (RASP-EEP)

Several series demonstrated, that EEP, especially HoLEP, provides similar outcomes to OSP [1]. Laser enucleation is, therefore, recommended as first-line treatment for large benign prostates [49]. RASP has a slightly longer indwelling catheter time (3d vs 2d) and hospitalization (4d vs 2d). However, Umari observed similar operative times [50] and similar clinical outcomes between RASP and EEP-HoLEP. (Table 4). Zhang [51] observed a high transfusion rate of 9.2% and longer operative times in only 32 RASP patients compared to 600 HoLEP patients, which might be explained by the small study subgroup and possible early robotic experience. Transfusion rate of RASP in general is reported to be about 3% in the literature [46].

Several authors discuss the possibly underestimated urethral trauma during EEP. In fact, HoLEP procedures require a 26F urethral sheath. Narrow urethras in small men might thus be damaged following long manipulation times, possibly resulting in urethral strictures. After RASP, urethral strictures very rarely occur with a reported incidence of 0.6% [24]. Urethral stricture rate after HoLEP procedures is reported with 3.3% [52], implying that urethral microtrauma during EEP might be underestimated. A higher percentage of bulbar urethral stricture rate of 4.8% was found by Shah et al. in prostates over 100 g, which may be explained by a longer urethral manipulation time [53].

Erectile function does not seem to be impaired substantially either by RASP or HoLEP evaluated with pre- and postoperative IIEF-scores [42, 54, 55] Placer et al. observed in 202 sexually active men after HoLEP a deterioration of erectile function in 12% and an improvement of IIEF of 7%. Loss of antegrade ejaculation after HoLEP varies between 70 and 80% [56]. Maintained antegrade ejaculation was reported by Wang et al. in 13/14 (93%) patients after urethral sparing RASP [42]. Integrity of the bladder neck and proximal prostatic urethra might play a crucial role in maintaining antegrade ejaculation. However, the impact of sexual function after RASP has not been studied thoroughly.

RASP seems to have a significantly shorter learning curve than EEP, especially HoLEP. Brunckhorst estimates the learning curve of HoLEP to be about 50 cases [57, 58] and complications occur in about 20% in the first 40 cases. In comparison, the learning curve of RASP is reported with 5–10 cases for surgeons with prior robotic experience [59]. However, the term “learning curve” cannot be directly translated to “operative quality”, as the experience curve of a surgeon never stops. Every skilled team will have good clinical outcomes if its operative technique is frequently used and trained within the entire team—including anesthesiology and nursing staff. Therefore, current guidelines for the treatment of LUTS due to large prostates recommend that clinicians should consider endoscopic, robotic, laparoscopic or open simple prostatectomy depending on their expertise with these respective techniques.

Conclusion

Robot-assisted simple prostatectomy reaches equivalent efficacy and clinical outcomes compared to the historical gold standard of open simple prostatectomy. In contrast to open simple prostatectomy, it is a minimally invasive technique with less blood loss and shorter hospitalization. Compared to endoscopic enucleation, the robotic approach causes less urethral trauma with potentially lower postoperative stress incontinence and has a shorter learning curve for surgeons in established robotic radical prostatectomy programs. However, with the lack of prospective randomized trials, potential benefits over transurethral laser enucleation techniques remain unclear. Nevertheless, robotic-assisted simple prostatectomy is being increasingly adapted. Robotic-assisted simple prostatectomy is certainly here to stay and should be considered as a standard to treat large benign prostate glands, especially because it also offers the option to treat concomitant pathologies like bladder diverticula or stones.