Bipolar Transurethral Resection of Prostate: Current Status in the Management of Bladder Outflow Obstruction

Introduction

The surgical management of benign prostatic hyperplasia (BPH) has traditionally been by transurethral resection of the prostate (TURP). This uses monopolar high frequency current which allows electroresection of prostatic tissue [1]. The procedure results in improvement of obstructive voiding, improvement in urinary peak flow, reduction in post void residual and symptom scores and is associated with a low initial failure to void rate [2,3]. Rassweiler et al. have recently published a large review of men who underwent monopolar TURP (mTURP) and assessed complications specifically associated with the procedure from various time periods [1]. Blood transfusion following intraoperative haemorrhage was required in as high as 22% in early series but has reduced to 0–7.1% in more recent series and transurethral resection (TUR) syndrome although rare (0–1.1% in recent studies), is associated with significant mortality [1]. Another recent large scale study on mTURP involving approximately 10,000 patients in 2002–2004 suggested that the mortality from the procedure was 0.1% and that the cumulative short term morbidity was 11% [3]. The most relevant complications were failure to void (5.8%), surgical revision (5.6%), significant urinary tract infection (3.6%), bleeding requiring transfusions (2.9%) and transurethral resection syndrome (1.4%) [3]. These contemporary studies have given us newer more realistic data on traditional TURP benefits and morbidity which will enable effective comparisons between newer technologies and techniques developed to treat bladder outflow obstruction and their outcomes. These newer modalities have been largely developed in an attempt to reduce the complications, which in some cases can be potentially life threatening, seen with TURP. These procedures have incorporated a number of lasers to vaporise or enucleate the prostatic tissue [2]. Another new technique utilises bipolar electrosurgical current and allows surgery to take place in a traditional TURP fashion but utilises normal saline as the irrigation fluid. In this setting prostatic tissue can be vaporised or resected.

In the opinion of the authors, who have experience in a number of bladder outflow surgical de-obstructing procedures, bipolar transurethral resection of the prostate (bTURP) is the procedure of choice. This is mainly due to the fact that the procedure allows surgery to take place in exactly the same way as traditional mTURP, allows specimens of prostatic tissue to be sent for histology and has an excellent side effect profile and is safer than mTURP. This review will focus on bTURP, explaining the technology and principles behind its use and will review the literature concentrating predominantly on randomised controlled trials.

Technology

Electrosurgery employs high-frequency electrical energy, attained through the conversion of standard electricity via a generator, to cut and coagulate tissue. The essential difference between monopolar and bipolar electrosurgical circuits is the position and distance between the active and return electrodes. Typically, in a monopolar circuit the active electrode is at the tip of the surgical implement with the return electrode being at distance, in the form of a large plate on the patient's skin. In bipolar circuits, however, both electrodes are in close proximity usually within the surgical instrument.

In mTURP the prostatic tissue impedes this energy, generating heat which is sufficient to vaporise intracellular water or denature intracellular proteins and hence achieve the desired cutting or coagulation. The remaining energy then requires excessive voltage to push the energy through the body to the return electrode. In order to avoid excessive dispersion of this energy a nonconductive low electrolyte hypo-osmolar fluid such as glycine or mannitol is required. The significance of this is the risk of excess absorption of irrigant solution and dilutional hyponatraemia with resultant TUR syndrome. In contrast, however, with bTURP these concerns are theoretically obliterated as isoosmolar physiological saline is utilised, owing to the minimal distance between the active and return electrodes. As energy flow is confined to the resection site, less energy and voltage are also required. The energy is transmitted from the resectoscope loop into the surrounding saline causing evaporation and the subsequent creation of a gas interface around the loop resistant to energy flow. Addition of voltage to this gas interface causes excitation of sodium ions to form a highly ionised plasma layer, which disrupts tissue at a molecular level allowing effective cutting of prostatic tissue. In order to achieve coagulation with the bipolar system, voltage is minimized to prevent plasma formation and consequently produce tissue-resistive heating, whereby vessel walls are ‘sealed’ through the dissipation of heat.

Bipolar technology was initially applied in the form of transurethral vaporisation of the prostate [4], however vaporisation does not allow histological assessment. Furthermore medium term results have questioned its efficacy in comparison to mTURP with inferior outcomes at 3 years follow-up [5]. Several devices have since been developed to perform bTURP and are outlined below.

Clinical efficacy

Although the long-term effects of bTURP are still to be established, many studies have shown the efficacy of bTURP to be comparable to that of mTURP in the short and medium term. Some critics of the technique may suggest that as tissue is resected along with some vaporisation and subsequent charring, prostatic chippings maybe suboptimal for analysis. Although this effect leads to potentially smaller tissue resection weights when compared to mTURP, the quality of tissue specimens obtained with bipolar resection has been proven to be comparable and thus not affecting histological examination [9]. In another study coagulation depth appeared to be superior with bTURP [10]. Furthermore a recent meta-analysis did not find a significant difference in resection weights between m- and bTURP [11].

Mamoulakis et al. performed a systematic review and meta analysis of randomised controlled trials published up to February 2009 comparing bTURP and mTURP [12]. Studies with vaporisation or hybrid vaporisation and resection were excluded. It was felt overall study quality was low in general with poor randomisation techniques and/or blinding and lack of statistical power in several studies. Seventeen studies were involved totalling 1406 patients. Pooled analysis of the five trials reporting on maximal flow rate (Q-max) values at 12 months follow-up showed a small statistically significant advantage of bTURP. However it was noted that this increase in Q-max was unlikely to be clinically relevant. No statistically significant difference in the improvement of International Prostate Symptom Score (IPSS) and Quality of Life (QoL) scores was identified in the pooled analysis of 4 and 3 trials, respectively, reporting on those variables at 1 year follow-up. Operative times were similar in the 2 groups. Another meta-analysis assessing several forms of bladder outflow surgery with conventional mTURP has also recently been reported with similar outcomes for m- and bTURP [11]. However they noted less catheter time post-operatively in favour of bTURP.

More recently a trial by Chen et al., involving 100 patients, showed no significant difference in improvement of IPSS or Q-max at 24 months post-operatively [13]. Similarly after 1 year of follow-up of 212 patients enrolled in a study by Engeler et al., no significant differences were found in IPSS score, improvement in Q-max, decrease in post-void residual volume and QoL assessment [14]. When assessing prostates >60g Michielsen et al. reported no significant difference in patient age, prostate size, PSA, uroflow rate, post voiding residual urine, operation time, catheterization time, and hospital stay between m- and bTURP [15]. However, with the mTURP group a significant drop in serum sodium was observed compared with the TURis group. One case of clinical TUR syndrome was observed in the conventional mTURP group.

Complications and safety profile

The use of normal saline as irrigating fluid eliminates the risk of dilutional hyponatraemia and TUR syndrome, a potentially fatal complication occurring in up to 1.4% of cases with mTURP in a modern series [3]. In the meta-analysis of RCTs published by Mamoulakis et al. including 1362 patients, TUR syndrome occurred in 13/681 with mTURP versus 0/681 with bTURP [12]. Interestingly, most individual trials reported non-significant differences between the two arms with regards to blood transfusion. However with regards to clot retention, pooled analysis of seven studies showed a significantly higher occurrence in the mTURP arm, with one less episode occurring for every twenty bTURPs performed. Furthermore a reduction in duration of irrigation after TURP seemed to favour bipolar resection [12]. Although trial protocols were variable and as a result a meta-analysis could not be formally performed there was a trend to reduced catheter times with bTURP.

Long term follow-up data on bTURP are still awaited and further studies are necessary to provide its long term safety profile. In early studies bTURP was associated with a higher incidence of meatal and urethral injury and stricture, possibly explained by the use of larger resectoscopes in the case of the PK system [16] or possibly due to the electrical current leaking via the sheath in the TURis system [6]. Although in the case of the latter, the manufacturer could not demonstrate any current leakage on testing [6]. Overall the numbers of strictures in the above series are very small and pooled analysis of differences in cumulative incidence rates at 12 months between mTURP and bTURP were insignificant [12]. In the recent RCT of 100 patients by Chen et al., rates of urethral stricture and bladder neck contracture were found in 6% of patients in the bTURP arm compared to 10% in the mTURP arm with a follow-up period of 2 years [13]. Furthermore in another study comparing TURis with mTURP, with approximately 250 patients in each arm, differences in stricture rates were insignificant between the groups being 1.4 and 2.5%, respectively [17].

No significant difference in the incidence of erectile and ejaculatory dysfunction in patients undergoing m- and bTURP has been found to date. Equal numbers of patients were found to suffer with erectile and ejaculatory dysfunction [18]. Chen et al. in their trial reported that of those patients still sexually active, 8 out of 22 patients (36%) in the bTURP arm, and 9 out of 18 patients (50%) in the mTURP had retrograde ejaculation with no significant reduction in erectile function noted in either arm [13].

In a recent study 16% of patients in the bTURP arm and 20% in the mTURP arm reported urge incontinence initially, which was found to be transitory and resolved within 6 months [13]. At 2 year follow-up, no patients who underwent bTURP and only 2 patients (4%) of those who underwent mTURP reported stress incontinence. No significant difference in stress incontinence incidence has been reported in another review [18].

Implications for training

In mTURP it is good practice to complete the operation within an hour usually and using the least amount of irrigating fluid in order to avoid electrolyte imbalance, TUR syndrome and excessive blood loss. This has obvious negative implications on trainees performing transurethral resections, with a low threshold for the supervising consultant to intervene. In bTURP the use of normal saline as irrigating fluid should result in less time constraints as resection time can be extended over the conventional hour. In theory in larger prostates, longer resecting times are possible in order to achieve adequate de-bulking. Conversely, with the potential for less bleeding and the potentially clearer visual field, this may translate into resection times that are comparable if not even shorter than with mTURP as the whole procedure may become more efficient. Furthermore the potential for better visualisation with bTURP is beneficial in allowing identification and thus avoidance of injury to structures such as the sphincter and prostatic capsule. For these reasons some trainees with experience in various surgical procedures for BPH have suggested bTURP would have been the most beneficial for them in the early part of their learning curve with TURP.

The Dartford experience

Surgeons at Dartford have performed >600 bTURPs over the years and have utilised this as their procedure of choice for the surgical management of BPH. To date only 1 patient (the first patient) has required a blood transfusion directly related to the surgery. No patient has developed TUR syndrome and they have not observed a higher than normal rate of stricture formation, an early concern with the technology. Approximately 70% of patients are able to be discharged within 24h of surgery, catheter free (personal communication IKD).

Conclusions

bTURP has been shown to have comparable efficacy to the current “gold-standard” of mTURP with the added benefits of no TUR syndrome, reduced catheter time and the potential for earlier discharge. The safer approach for patients together with the improved visual field and reduced time constraints for resection means that both patients and trainee surgeons may benefit from the use of bTURP and further research with longer term follow-up and cost effectiveness analysis is warranted.