Surgical outcomes of transurethral enucleation with bipolar energy for benign prostatic hyperplasia: single surgeon’s initial experience

Abstract

Background

Transurethral enucleation with bipolar energy (TUEB) is one of endoscopic enucleation methods for the surgical treatment of benign prostatic hyperplasia (BPH). Authors investigated initial outcomes of TUEB performed by a single surgeon.

Methods

From 04/2016 to 06/2021, prospectively collected clinical data of 387 patients who underwent TUEB were retrospectively analyzed. TUEB was performed by transurethral resection in a saline system with a spatula loop (one-lobe enucleation technique). Patients were stratified by surgery period (early vs. late) and evaluated perioperatively.

Results

A total of 387 patients were included in the final analysis. Mean age was 72.4 years and total prostate volume was 73.1 cc as in the whole group. Total procedure time (116.0 vs. 116.8 min, p = 0.863), detailed procedure time (enucleation: 49.2 vs. 46.1 min, p = 0.099; morcellation: 26.5 vs. 23.6 min, p = 0.162) and enucleated tissue weight (26.1 g vs. 27.9 g, p = 0.350) did not differ significantly between groups. However, there were significant differences in enucleated tissue weight per unit time (g/min) (0.52 vs. 0.58, p = 0.037), reoperation rates due to bleeding (9.8% vs. 2.5%, p = 0.002), and conversion to transurethral prostatectomy (TURP) (19.2% vs. 1.5%, p < 0.001). At 6 months post-operatively, there were insignificant differences in the rates of de novo stress incontinence (p = 0.188), urethral stricture (p = 0.158), and bladder neck contracture (p = 0.477).

Conclusion

TUEB is a safe and effective technique for the treatment of BPH, resulting in significant improvements in both subjective and objective symptoms. With increasing surgical experience, efficacy of the procedure has significantly improved in terms of both bleeding complication rates and TURP conversion rates.

Clinical trial number

Not applicable.

Introduction

Recently, as an endoscopic enucleation method for the surgical treatment of benign prostatic hyperplasia (BPH), researchers in Japan developed transurethral enucleation with bipolar energy (TUEB) using the transurethral resection in saline (TURis) system and the TUEB loop to enable prostatic adenoma enucleation in hospitals that lack laser system [1]. The TUEB technique utilizing the novel loop was initially developed by Ken Nakagawa [2]. This technique is characterized by adenoma enucleation by the TUEB loop into the bladder, followed by enucleated adenoma removal by morcellation. In consideration of hospitals without a morcellator, Hirasawa et al. then reported on the safety and efficacy of a different TUEB technique using only the TUEB loop and TURis system [1]. That retrospective study demonstrated that TUEB was superior to bipolar energy transurethral resection of the prostate (TURP), with less blood loss as well as a decreased length of hospital stay (LOS) with equivalent efficacy at 1-year follow-up [1]. They subsequently reported on the safety and effectiveness of TUEB as a surgical procedure. The relief from bladder outlet obstruction also proved to be durable at 2-year follow-up [3].

Theoretically, TUEB uses normal saline for irrigation instead of glycine, which minimizes the risk of hyponatremia, even when resecting or enucleating large prostatic glands. Compared to TURP, this technique results in less frequent bleeding and tissue charring, which leads to a significantly shorter recovery time. With TUEB, the operator can perform resection, vaporization, and enucleation using a single device, which has advantages for intraoperative hemostasis and specimen removal after enucleation. While the number of conventional TURP procedures performed per year remained relatively static over the period from 2010 to 2017 (6,801 → 6,645), there was a significant increase (278 → 3,805) in the number of holmium laser enucleation of the prostate (HoLEP) procedures conducted in South Korea [4]. While HoLEP has shown comparable or even better surgical outcomes than TURP, and while it is preferred by many urologists due to fewer postoperative complications [5], conventional TURP is still widely recognized as the gold standard surgical treatment for BPH. This is because most centers have basic TUR equipment and can consistently perform TURP procedures accurately and efficiently. There have also not been many studies reporting on the TUEB experience of single surgeons. Therefore, the present study investigated the outcomes of TUEB performed by a single surgeon.

Materials and methods

Patients and perioperative evaluation

From April 2016 to June 2021, 387 patients underwent TUEB by a single surgeon. Clinical data, perioperative characteristics and surgical outcomes were prospectively collected for all patients and retrospectively analyzed for the purposes of this study. The data capturing the patients’ clinical information were accessed from 29 January 2022 to 30 June 2022. Patients were arranged in chronological order according to the date of surgery and then divided in half using a simple dichotomy, with the first half of the patients in the early period group and the second half in the late period group (early period vs. late period). Patients with bothersome Lower Urinary Tract Symptoms (LUTS) were offered surgery in cases involving preoperative International Prostate Symptoms Score (IPSS) ≥ 12 points; quality of life (QoL) ≥ 4; maximal urinary flow rate (Qmax) < 15 mL/s; post-void residual urine volume (PVR) > 50 mL; a lack of response to medical therapy; and/or a lack of willingness to undergo medical therapy. The benefits and harms of surgical treatment relative to other conservative/medical options were extensively discussed with all patients. Patients with renal impairment, neurogenic bladder, bladder stones, prostate cancer, history of prostatic or urethral surgery, and/or hydronephrosis were excluded from this study. All the patients met the inclusion criteria. This study was approved by institutional review board (IRB number: B-2202-737-107, Clinical trial number: not applicable). Ethics approval and consent to participate all procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committees and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. Informed consent was obtained from all subjects involved in the study.

The routine pre-operative assessment included measurement of prostate specific antigen (PSA), along with evaluations of prostate volume (PV) and Qmax through transrectal ultrasonography and uroflowmetry, respectively. Patients were also invited to complete the IPSS and overactive bladder symptom score (OABSS) questionnaire for objective quantifications of baseline LUTS severity [6, 7]. As recommended by the current European Association of Urology Guidelines, we offered TUEB as a surgical option to relieve LUTS/BPO in men with prostate volumes > 30 ml [8, 9]. There was no predetermined upper limit on prostate size that could be treated by TUEB. Prior to surgery, urine culture was tested for each patient and those with positive urine culture were treated on the basis of the antimicrobial susceptibility test. All patients received a preoperative wide-spectrum antibiotic prophylaxis (second-generation cephalosporin if not contraindicated). A total of 127 patients were on anticoagulant agents, and all patients were instructed to cease taking them 2–7 days prior to surgery, according to the patient’s condition. All surgeries were performed in the same tertiary referral center skin-to-skin by a single expert surgeon (S.J.J.) (> 100 cases).

The operation time, including both enucleation and morcellation times, is defined as the interval between the insertion of the surgical instrument into the patient’s urethra and the insertion of the urethral catheter. The protocol of voiding trial was as follows: Patient’s catheters were removed without retrograde normal saline filling. Patients were instructed to void within 3 h or when sufficient desire-to-void was reached. Patients in both groups were measured for voided volume (VV) and PVR via bladder scan, based on which the attending physician determined whether the patient was fit for discharge. Patients were instructed to attempt secondary voiding trial if PVR > 150 mL was identified or VV was inadequate for accurate assessment of urinary retention (VV < 150 mL). Patients unable to void after two trials were re-catheterized and instructed to return to the outpatient clinic for catheter removal and voiding trials within 1 week [10]. Hemoglobin tests were not routinely done immediately after surgery unless patient’s vital signs are unstable.

Follow-up visits were scheduled at 1, 3, 6, and 12 months. Each follow-up examination included the total sum of IPSS & OABSS scores, IPSS-QoL score, uroflowmetry with PVR measurement, and a stress test to measure the degree of incontinence. All complications that occurred perioperatively were analyzed according to the modified Clavien-Dindo (CD) classification.

Surgical procedures

TUEB was performed using the TURis system (Olympus) with a TUEB spatula loop, which is characterized by a spatula attached to a standard tungsten wire loop. A 26-Fr continuous-flow resectoscope was used and the one-lobe enucleation technique was implemented in most patients. TUEB involved enucleation of the prostate using the Olympus SurgMaster (Olympus Europa Holding GmbH, Hamburg, Germany) TURis system and the TUEB loop. After cystoscopy, resection was made at the 12 o’clock position, followed by another at the 6 o’clock position to enucleate the lateral lobes in the case of bilobular hypertrophy. In the case of trilobular hypertrophy, resection was made at the 12 o’clock position, followed by another at each of the 5 and 7 o’clock positions. Next, mucosa at the apical adenoma was incised circumferentially. These grooves were deepened to the level of the surgical capsule. Both of the lateral lobes and middle lobe were dissected off the surgical capsule in a retrograde fashion from the apex towards the bladder using the TUEB loop along with arrest of bleeding. The TUEB loop moves in exactly the same plane as the surgeon’s index finger when performing open simple prostatectomy [3]. Rather than releasing the lobes into the bladder, they were left attached at the bladder neck by a narrow mushroom-like pedicle. Fragmentation of the enucleated lobes hanging at the bladder neck was performed by traditional electrocautery wire loop resection, while the devascularized lobes were still connected to the surgical capsule by a narrow pedicle (the ‘ mushroom ’ technique) [11]. Spinal or general anesthesia was administered as appropriate in each case. A 26-F continuous-flow resectoscope (Olympus, Tokyo, Japan) and an Olympus UES-40 SurgMaster electrical current generator were used with settings of 200 W for cutting and 120 W for coagulation.

Statistical analysis

The baseline characteristics and postoperative outcomes were compared between subgroups. The frequencies and proportions of each categorical variable were compared using chi-square test or Fisher’s exact tests, as appropriate. For continuous variables, means and standard deviations were compared using the results of one-way analysis of variance (ANOVA) after normality and variance-equivalence tests. For abnormally-distributed continuous variables, median values and interquartile ranges were compared using Kruskal–Wallis tests. As for individual CD grade complication rates specifically, Fisher’s exact test (CD grade I & II) and chi-square test (CD grade III), with significance thresholds of 0.05, were utilized to determine if there is any significant difference between groups. All statistical tests were conducted at a two-sided significance level of 0.05 using SPSS 22.0 (IBM Corp., Armonk, NY). A p value < 0.05 was considered to indicate statistically significant difference.

Results

Baseline Qmax was 9.5 mL/sec when PVR was measured at 106.6 cc. Total prostate and transitional volumes were found to be 73.1 cc and 42.1 cc, respectively. 126 patients with urinary retention underwent preoperative catheterization before surgery. In terms of preoperative baseline characteristics, total operation time (116.0 min vs. 116.8 min, p = 0.863), detailed procedure time (enucleation time: 49.2 min vs. 46.1 min, p = 0.099; morcellation time: 26.5 min vs. 23.6 min, p = 0.162), and enucleated tissue weight (26.1 g vs. 27.9 g, p = 0.350), there were no significant difference between groups. There were also no significant differences between groups in terms of the rates of preoperative urinary retention history (33.2% vs. 32.0%, p = 0.801) or immediate postoperative urinary retention requiring catheterization (7.8% vs. 8.2%, p = 0.988) (Table 1). As normal saline was used for irrigation during surgery in all cases, there were no episodes of postoperative hyponatremia. Fifty-one patients with PSA elevation underwent a prostate biopsy immediately prior to surgery under general anesthesia. Twenty-nine patients were diagnosed with prostate cancer, 19 of whom underwent prostate biopsy and 10 were diagnosed from morcellated tissue fragments.

Table 1 Baseline characteristics and perioperative outcomes

There were significant differences observed in enucleated tissue weight per time unit (g/min) (0.52 vs. 0.58, p = 0.037), rate of reoperation (all transurethral coagulation) due to bleeding (9.8% vs. 2.5%, p = 0.002), and rate of conversion to transurethral prostatectomy (TURP) (19.2% vs. 1.5%, p < 0.001). Reason for TURP conversions was mostly for bleeding control. With a median follow-up of 11.0 months, there were no significant differences observed at postoperative 6 months between groups in terms of the rate of de novo stress incontinence (1.4% vs. 4.4%, p = 0.188), urethral stricture (0% vs. 0.8%, p = 0.158) or bladder neck contracture (0.7% vs. 0%, p = 0.477). Overall postoperative complication rate was 10.3% (40/387) with insignificant difference between groups (Early group: 12.4% vs. Late group: 8.2%, p = 0.176). There was significant difference in the severity (CD grade I: p = 0.033, II: p = 0.013, III: p = 0.003) of postoperative adverse events between the groups based on the CD grade. There were 5 postoperative uncomplicated urinary tract infection (UTI) cases, which comprises CD grade II, that resolved with oral antibiotic therapy in the outpatient setting without preoperative or refractory UTIs. There was no de novo erectile dysfunction case, or broken loop case during operation. All cases classified as CD grade I (i.e., cases involving urinary retention only) were successfully treated with catheterization alone without medication. All CD grade III cases (those involving hematuria with some urinary retention) were resolved primarily through transurethral coagulation surgery, with catheterization prior to surgery in some cases (Table 2).

Table 2 Complications and follow-up results of voiding parameters

Within the group, the post-operative IPSS, IPSS-QoL, and OABSS scores were all significantly different from the corresponding values in the pre-operative period, thus indicating postoperative symptom improvement. These differences were more pronounced in the IPSS questionnaire results than they were in the OABSS results (Fig. 1). There were no significant differences in questionnaire scores between the groups in the pre- and post-operative follow-up periods (all p > 0.05) (Fig. 1).

Fig. 1

Perioperative results of IPSS & OABSS questionnaires

Discussion

Recent advances in energy and technology have led to the emergence of various new types of transurethral surgical therapies, such as laser, bipolar energy enucleation, or vaporization, and aquablation, which has led to diversified BPH treatment [12]. Although there has been a growing amount of literature reporting on such treatments, the relationship between TUEB and other techniques in the management of BPH remains unclear. One meta-analysis [13] revealed that, compared to TUEB, HoLEP had a shorter catheterization time (p = 0.007), higher operative time (p = 0.03), higher enucleation weight (p = 0.01), and shorter bladder irrigation time (p = 0.01). However, there were no significant differences observed between the techniques in terms of transfusion rates, complications, LOS, or postoperative functional outcomes at 1, 3, 6, 12, or 24 months.

From our point of view, there is a difference in technique between performing HoLEP and TUEB for BPH. Regarding prostate mucosal notation, the position of the mucosa that is indicated in both techniques is similar in that, in both cases, an incision is applied to the area around verumontanum starting at 6 o’clock and heading to the capsular membrane at 12 o’clock. Meanwhile, when performing groove formation at 6 and 12 o’clock, in the case of HoLEP, the prostatic median lobe is enucleated from verumontanum in the direction of the bladder neck, while in the case of TUEB, the median lobe is excised to form a groove, and then also expanded to both sides following resection of the tissue at apex in 12 o’clock. Regarding surgical plane formation and enucleation, in HoLEP, it is easy to form the surgical plane due to the vibration of the laser; meanwhile in TUEB, it is easy to find a plane using a resectoscope or loop as if one is using a broom. When dealing with prostatic apex, in HoLEP, the incision started from 12 o’clock and was pushed down to both sides with a laser, but in TUEB, the hanging tissue is cut off with a cutting current. Regarding hemostasis, in HoLEP, the laser is irradiated until hemostasis occurs by stopping at the bleeding focus, but in TUEB, immediate hemostasis is easy using the loop at the same time of enucleation. Finally, when removing peeled tissue, in HoLEP, morcellation is performed and the remaining tissue in the fossa is cut off with a laser; by contrast, the tissue can be cut off by the loop as well as morcellation in TUEB [14]. It is ultimately concluded that HoLEP is definitely advantageous for surgical plane formation and tissue incision during the enucleation process [15], but that TUEB has more advantages for hemostasis and tissue removal after enucleation, thus providing a wide range of options [16]. Another network meta-analysis [17] showed that TUEB appeared to have superior efficacy compared to monopolar TURP and open prostatectomy in BPH with volume > 60 cc. The bipolar energy system can effectively reduce the pressure in the bladder, relieve bladder outlet obstruction, and restore the physiological function of the bladder detrusor muscle, ultimately improving urination function [17, 18].

One of the most prominent aspects of our findings is that the enucleation efficacy increased along with chronological time. This parameter is expressed as a simple fraction consisting of a numerator (enucleated weight) and a denominator (enucleation time), and this ratio was found to be increased in the ‘Late group’. This indicates that the surgeon can successfully enucleate more adenoma as they accumulate surgical experience. A prior study conducted by a single surgeon [3] suggests that TUEB has a steep learning curve, but that its effectiveness increases significantly after 50 completed procedures. In line with this finding, the rate of reoperation due to bleeding and conversion to TURP was also decreased. With accumulated operation cases, it is expected that a surgeon’s skills in hemostasis will become more sophisticated to achieve better bleeding control and a clearer operative field to reduce reoperation and technique conversion. In the subsequent follow-up cohort of patients analyzed in this study by the same surgeon, the efficiency of enucleation was evaluated according to prostate volume size. The results demonstrated that enucleation efficiency increased with increasing prostate volume (Prostate volume < 40 cc, 40-80 cc, & ≥80 cc: 0.36, 0.44, & 0.73 g/min, respectively) [19]. Furthermore, no significant differences were observed in functional outcomes or complications. These findings might be attributed to the superior hemostatic properties of the loop utilized during TUEB.

Nevertheless, some of our findings require further elucidation and detailed interpretation. First of all, as a surgeon with over 300 HoLEP procedures and also comparable number of conventional TURP procedures (relative more familiar and faster technique than TUEB), there might be little delay in decision-making regarding the conversion to TURP, which may have resulted in prompt conversion to TURP in real clinical operation field. Therefore, total operation time difference between the groups might not be significant. Secondly, prolonged LOS cases were observed in our cohort. One of the reasons for prolonged LOS was some patients’ personal circumstances, such as a desire to restart anticoagulants during the hospitalization. In the majority of other cases, the hematuria did not sufficiently improve to warrant decatheterization and discharge from the hospital. Thirdly, there was no significant difference in total OABSS questionnaire score between preoperative, postoperative 1 & 3 month. A study [20] revealed that older age was associated with a slower decline in total OABSS questionnaire score following HoLEP. Furthermore, a study reporting the outcomes of 3,000 South Korean HoLEP patients [21] did not report a statistically significant difference in the reduction of total OABSS scores at postoperative two weeks and three months compared to the baseline. These findings are believed to be applicable to ours in that we evaluated outcomes after enucleation technique, although different type of energy was used. Finally, our study showed relatively small resected weight compared to others [1, 13]. this result can be related to the surgeon’s learning curve. In our previous study [22], 70 cases will make comparable efficiency of TUEB and a systemic review [23] reported that TUEB requires approximately 40 cases to 50 cases to overcome learning curve. One recent multicenter study only needs twenty cases to achieve acceptable outcome of bipolar enucleation [24]. Notwithstanding the relatively modest resected weight, there was a significant improvement in enucleation efficiency (enucleated tissue weight per time unit) in the late group. Although those literature indicates that cases needed to achieve proficiency might vary according to level of experience, TUEB is a relatively straightforward technique that can be mastered in a few dozen, not hundreds, of cases, making it easily feasible to a broad range of surgeons. One of our findings is that there was a significant difference in the distribution of CD grades. This may be attributed to the explanation that as experience was gained, the proficiency in controlling bleeding improved, which subsequently led to a reduction in postoperative complications related to hematuria. Also, significant difference in the rate of CD grade I might be due to the relatively higher number of cases with urinary retention, in the late group, without hematuria than cases with hematuria and urinary retention.

The present study is not devoid of limitations that must be noted. The first is the retrospective nature of the study, although we set up a prospectively maintained database, which was then analyzed retrospectively. Moreover, the lack of randomization could be another limitation; however, there were no significant differences found between the groups, so this bias was likely minimized. Another important limitation of our study is the narrow application of TUEB’s learning curve to other cohorts. As the single surgeon performed over 300 cases of HoLEP before initiating TUEB, the case number needed to overcome the learning curve might be less than the expected number, although this was not fully evaluated in the current study. Another limitation is that the grouping of total patients was arbitrary, as they were classified into the first half and the second half by the chronological date of their surgery. This might not reflect the exact timing of overcoming the learning curve. Meanwhile, in order to minimize the impact of BPH complications on the surgical outcome, our analysis was limited to patients with uncomplicated voiding problems, without complications or underlying medical conditions, or whose medications for BPH were ineffective. This might differ from the methodology employed in other studies that have included patients who underwent surgery due to complications of BPH. Also, there was some follow-up losses. Although there was no follow-up loss at postoperative 1 month, 30 patients were lost to follow-up at postoperative 3 months (Early group: 4 patients & Late group: 26 patients). At postoperative 6 months, 96 patients were lost to follow-up (Early group: 52 patients & Late group: 44 patients). Moreover, the limited sample size for CD grade I and II in each group necessitates a cautious approach to the interpretation of the statistical significance observed in the comparison of CD grades. It is important to recognize that these findings may not necessarily translate into clinical significance. Lastly, as this is a single-center single surgeon series with a relatively short follow-up period, physicians should be cautious when applying our experience to their own cohorts.

Conclusions

The use of a novel spatula loop in TUEB has been demonstrated to be a safe and effective technique. With increasing surgical case load, the efficiency of TUEB, as deduced from the enucleated tissue weight per time unit, improves, while the proportion of bleeding-related complications and conversion to conventional TURP decreases significantly. Our TUEB technique could be safely adopted in centers lacking access to laser systems, surgeons with any level of experience in TURP, or in patients with high bleeding tendency. A larger multicenter study with long-term follow-up is required to validate our findings across diverse surgical settings and assess the durability of outcomes and complications reported in this study.