Robot-assisted radical prostatectomy (RARP) is an established treatment for localized prostate cancer, providing durable oncologic control with a 15-year cancer-specific survival of 97% [1]. However, urinary incontinence and erectile dysfunction remain the principal adverse effects of RARP, significantly impacting postoperative quality of life [2]. To mitigate these functional sequelae, nerve-sparing (NS) techniques have been developed and are now widely adopted [3]. Preservation of the neurovascular bundle (NVB), which courses mainly along the dorsolateral aspect of the prostate, is critical for maintaining both erectile function and urinary continence [4].

Since the seminal description of NS radical prostatectomy by Walsh and Donker [5] in 1982, advances in understanding of neurovascular anatomy and neural injury mechanisms have driven continual refinement of NS techniques, particularly in the era of robotic surgery [6]. NS can be performed in an antegrade fashion (from base to apex) or retrograde fashion (from apex to base) [7]. The retrograde approach facilitates early identification and release of the NVB prior to prostatic pedicle ligation, reducing the risk of inadvertent injury and potentially attenuating neuropraxia [8]. Our institute previously demonstrated that the retrograde NS technique significantly improved early potency recovery compared with the antegrade NS technique, achieving 80.8% vs. 65.0% recovery at 3 months and 90.1% vs. 72.1% at 6 months [7]. Accordingly, we have adopted the retrograde approach as the standard technique in our current practice [9].

Nonetheless, retrograde NS in patients with large prostates remains technically demanding. The mass effect of an enlarged prostate gland distorts anatomical planes and limits pelvic working space, particularly impeding posterior dissection from Denonvilliers' fascia. In our series, the rate of full NS surgery declined markedly with increasing prostate volume—from 38.3% in prostates <50 g to 20.1% in prostates 100–150 g and 13.7% in prostates >150 g [10].

In this context, we present a case of bilateral NS RARP in a patient with a 124 cc large prostate, highlighting key elements of the retrograde NS technique, which was refined through experience with over 19,000 RARP cases at a high-volume referral center. Our aim is to share practical insights to optimize functional and oncologic outcomes in this challenging surgical scenario.

The patient is a 68-year-old man. He had an elevated prostate-specific antigen (PSA) level of 7 ng/mL and subsequently underwent a transperineal prostate biopsy. The biopsy revealed Gleason score 3 + 3 disease in the right lateral and medial posterior peripheral zones, involving two out of 11 biopsy cores. Following staging, he was diagnosed with clinical stage T1cN0M0 prostate cancer. His MRI showed an enlarged prostate measuring 67 mm × 58 mm × 61 mm (longitudinal, anteroposterior, and transverse; estimated volume 124 cc), with a Prostate Imaging Reporting and Data System category 4 lesion (0.9 cm) located in the anterior transitional zone of the medial portion of the right lobe. After informed decision-making, he underwent robot-assisted radical prostatectomy, using Da Vinci 5 robotic surgical system^® (Intuitive Surgical, Sunnyvale, CA, USA). This study used de-identified data from an IRB-approved outcomes registry (IRB no. 237998).

Conventional RARP was performed using a six-port transperitoneal approach, as summarized in Table 1. An 18 Fr Foley catheter was placed after sterile draping. Pneumoperitoneum was established at 10 mmHg using the AirSeal system. Following port placement and docking, the patient was positioned in a 26-degree Trendelenburg position. Monopolar curved scissors were used in the right robotic arm, long bipolar grasper in the left arm, and ProGrasp forceps in the fourth arm.

Table 1 . Our stepwise robot-assisted radical prostatectomy techniques.

Step	Surgical step
1	Port placement
2	Bladder dropping (Retzius space development)
3	Bladder neck transection (anterior approach)
4	Seminal vesicle dissection
5	Posterior dissection
6	Retrograde nerve-sparing (lateral dissection)
7	Apical dissection
8	Division and ligation of the dorsal vascular complex
9	Urethral division
10	Posterior reconstruction
11	Vesicourethral anastomosis
12	Peritoneal flap (only if pelvic lymph node dissection is performed)
13	Port site and skin closure

The procedure commenced with peritoneal incision and division of the bilateral median umbilical ligaments, followed by development of the Retzius space. Peritoneal incisions were extended laterally to the level of the vas deferens and completely exposed the pubic bone. This incision allowed the bladder to be mobilized and dropped for optimal exposure of the anterior prostate and bladder neck. The anterior surface of the prostate was defatted.

The anterior bladder neck was divided using a combination of sharp dissection and cautery without opening the endopelvic fascia. After exposing the Foley catheter, it was used to elevate the prostate. The posterior bladder wall was then inspected to identify the ureteral orifices, and further dissection posteriorly exposed the vas deferens and seminal vesicles. Both seminal vesicles were dissected and secured with Hem-o-lok clips while maintaining their structural integrity.

Subsequently, Denonvilliers’ fascia was incised to develop the retroprostatic plane. The rectum was meticulously released from the posterior aspect of the prostate. To facilitate precise neurovascular bundle dissection, the camera was alternated between 30-degree up and down views (toggling technique) [11]. Dissection between the neurovascular bundles and the prostatic fascia was performed bilaterally in an intrafascial plane, progressing posteriorly toward the apex, with careful preservation of the neurovascular structures (Fig. 1).

Figure 1. Intraoperative view of connecting the lateral and posterior planes. Lateral dissection was carried out until the posterior neurovascular plane was reached. The prostatic pedicles were secured with Hem-o-lok clips to ensure hemostasis.

The endopelvic fascia was then incised at the base of the prostate laterally while preserving the levator fascia. Lateral dissection continued until the posterior neurovascular plane was reached. The bilateral prostatic pedicles were secured with Hem-o-lok clips for hemostatic control (Fig. 2).

Figure 2. Intraoperative view of posterior dissection. A camera angle was alternated to a 30-degree up view (toggling technique) to enhance visualization of the posterior aspect in case of a large prostate.

During apical dissection, the dorsal vascular complex was carefully divided and subsequently ligated with a running 2-0 barbed monofilament suture (Quill^TM Barbed Suture). The urethra was then divided distal to the prostatic apex using sharp dissection, with attention to preserving as much urethral tissue as possible. The Foley catheter was withdrawn, and the posterior urethra was divided. The remaining attachments at the posterior apex of the prostate were sharply dissected to complete prostate removal.

Bladder neck reconstruction was performed using a 2-0 barbed suture (Quill^TM Barbed Suture), and posterior reconstruction was conducted according to a previously described technique using a “Rocco stitch” [12]. Urethrovesical anastomosis was completed using a running bidirectional barbed suture.

Total operative time was 80 minutes, with an estimated blood loss of 100 mL. The patient was admitted overnight and discharged the following morning without perioperative complications. His Foley catheter was removed on postoperative day 5 following confirmation of no leakage at the anastomosis site.

Achieving optimal functional outcomes while maintaining oncologic safety remains a central goal of contemporary RARP. A large prostate size introduces significant technical challenges for optimized NS owing to distorted anatomy and limited working space. Retrograde NS, however, remains a feasible and versatile technique that can be safely applied even in this anatomical complex setting. In this video (Supplementary Video 1), we present a step-by-step application of our retrograde NS technique in a patient with 124 cc prostate. Despite the technical challenges associated with large prostate size, retrograde NS combined with the toggling technique enabled safe and effective preservation of the NVB. This procedure offers distinct advantages in facilitating precise NVB dissection, resulting in favorable perioperative outcomes, with no complications and early discharge.

The retrograde technique allows for early release of the NVB prior to pedicle ligation, thereby reducing the risk of traction and thermal injury. Notably, we advocate for a graded NS strategy, tailoring the extent of dissection based on intraoperative oncologic risk and anatomical findings, rather than employing a binary all-or-none approach. We have previously described this graded approach as a systematic method for adjusting the degree of NVB preservation in real-time during surgery [13]. This five-grade system utilizes the relationship of the dissection plane to the landmark artery, in conjunction with visual cues such as pearly areolar tissue, to guide the extent of NS intraoperatively. Further, the landmark artery serves as a critical guide during retrograde NS (Fig. 3). Medial dissection relative to the landmark artery results in substantially greater preservation of nerve tissue (median 0 mm², interquartile range 0–3 mm²) compared to lateral dissection (median 14 mm², interquartile range 9–25 mm²) [14]. Use of the landmark artery as an intraoperative guide enhances both the precision and reproducibility of the dissection. In this case, bilateral full nerve-sparing (100% preservation on both sides) was achieved; however, the landmark arteries, which can typically be identified in approximately 73% of cases [14], were not visualized on either side. Nevertheless, we were able to enter the optimal intrafascial plane while using the toggling technique.

Figure 3. Intraoperative view of the landmark artery. (A) Right-sided landmark artery visualized during posterior dissection. (B) Left-sided landmark artery visualized during dissection connecting the lateral and posterior planes. The landmark artery serves as an anatomical guide to graded nerve-sparing dissection. Medial dissection along this artery enables complete or almost complete nerve preservation by consistently guiding the surgeon to the optimal intrafascial plane.

The toggling technique is the key adjunct to the retrograde approach. After incising the Denonvilliers’ fascia, we work between an avascular plane to release the posterior NVB from 5 to 1 and 7 to 11 o’clock positions on the right and left side, respectively [9]. During posterior dissection, toggling the camera from 30° down to 30° up is useful for facilitating early retrograde release of the NVB, particularly helpful in challenging large prostate cases, where limited working space can obscure conventional tissue planes. The toggling technique enables clear visualization of the medial side of the NVB, allowing the surgeon to enter the optimal intrafascial plane and reduce the risk of inadvertent NVB injury. In a propensity score-matched study, Shim et al. [11] demonstrated that the toggling technique significantly improved surgical facilitation and recovery of erectile function after RARP. Specifically, the use of the toggling technique resulted in higher tunneling success rates, defined as the ability to create a distinct dissection plane between the prostatic capsule and the preserved NVB (87% vs. 74%, p < 0.001). Moreover, the toggling group showed superior early erectile function recovery at 3 months (47% vs. 35%, p = 0.013), with a higher overall potency rate at 1 year (82% vs. 75%, p = 0.047). Therefore, we routinely incorporate toggling into our posterior dissection workflow and consider it an indispensable component of high-quality retrograde NS. In our experience, the ability to achieve consistent tunneling facilitates safe and efficient retrograde dissection, which is critical to optimizing functional outcomes even in challenging cases.

We also routinely attempt to preserve the accessory pudendal artery, an artery coursing along the periprostatic region, due to its potential role in promoting postoperative potency recovery, although we could not identify it in the present case (Fig. 4). While the clinical relevance of preservation of the accessory pudendal artery remains controversial, anatomical studies have shown that the accessory pudendal artery may serve as an alternative or supplementary source of penile arterial supply, especially in patients with compromised internal pudendal arteries [15]. Robotic surgery facilitates the precise and feasible identification and preservation of these arteries [16]. When combined with meticulous nerve-sparing techniques, accessory pudendal artery preservation may further contribute to the recovery of erectile function following RARP.

Figure 4. Intraoperative view of the accessory pudendal artery. The accessory pudendal artery is observed running along the left lateral aspect of the prostate. This artery may contribute to penile arterial supply.

However, it is essential to recognize that potency recovery is multifactorial. While meticulous surgical technique—including the precision of NS—strongly influences outcomes, patient factors such as age, baseline erectile function, comorbidities, and tumor characteristics also play critical roles. In our series, NS grade, along with preoperative Sexual Health Inventory for Men score, age, and pathological T stage, were the most significant determinants of postoperative erectile function recovery [17]. Moreover, the large prostate volume itself is independently associated with delayed and reduced potency recovery [10]. Therefore, comprehensive preoperative counseling remains vital to ensure realistic patient expectations and optimize satisfaction after surgery.

In summary, retrograde NS with toggling technique represents a valuable technique for optimizing NVB preservation in patients with large prostates. We believe that this approach can be safely and effectively applied even in anatomically challenging cases. When performed judiciously within an individualized, anatomically informed surgical strategy, it can contribute meaningfully to improved potency recovery while maintaining oncologic safety.

All authors have no conflicts of interest to declare.

No external funding was received for this research.

None.

Conceptualization: YO. Data curation: YO. Investigation: YO. Methodology: YO, SS. Supervision: VP. Visualization: YO. Writing – original draft: YO. Writing – review & editing: SS.

Video 1. This video demonstrates a step-by-step retrograde nerve-sparing technique with toggling during robot-assisted radical prostatectomy in a patient with a 124 cc prostate. It highlights key technical maneuvers to optimize neurovascular bundle preservation, with the goal of minimizing traction and thermal injury even in anatomically challenging cases.