The Risk Factor and Outcome of Transient Incontinence After Prostate Enucleation Surgery

Lower urinary tract symptoms caused by benign prostatic hyperplasia (BPH) are the most common urological problem among men. Approximately one-third of men over the age of 50 are affected by this problem. Surgical intervention is the most effective treatment for BPH, with around 100,000 procedures carried out annually in the United States. Of all surgical treatments, monopolar transurethral resection of the prostate (TURP), in which the enlarged prostate tissue is resected piece by piece using a monopolar electrode, has been the gold standard since the 1970s. It can substantially improve the maximal flow rate (Qmax), urinary symptoms (International Prostate Symptom Score, IPSS), and health-related quality of life (QOL), with long-term efficacy compared to medications or other minimally invasive treatments. However, monopolar TURP is a risky procedure because of the likelihood of severe complications such as massive bleeding or transurethral resection (TUR) syndrome. Therefore, it is of paramount importance to develop minimally invasive surgical techniques with outcomes similar to those of monopolar TURP, but with fewer side effects.

Since the 2000s, new energy systems for BPH surgical interventions quickly became popular, including systems that use bipolar energy and various laser systems, such as the holmium laser, potassium-titanyl-phosphate (KTP) laser, thulium laser, and diode laser. The trend in BPH surgical therapy has shifted from monopolar TURP to laser therapies and bipolar TURP over the past 10 years. Bipolar energy can be used to incise, resect, and vaporize prostate tissue using different electrodes. Holmium and thulium laser beams are mainly absorbed by water and act as incisional lasers. The KTP laser is selectively absorbed by hemoglobin and debulks prostate tissue through vaporization. The diode laser is absorbed by water and hemoglobin can therefore vaporize and incise prostate tissue. These new methods all use normal saline instead of distilled water to avoid hyponatremia. They can be further divided into three types according to their treatment principles: resection methods (resection of prostate tissue piece by piece), vaporization methods (vaporization of excessive prostate tissue), and enucleation methods (peeling the enlarged prostate from the prostate capsule).

Enucleation methods was proved to have better Qmax and IPSS after surgery than vaporization and resection methods. In a network meta-analysis, enucleation methods, including bipolar enucleation of prostate , holmium, thulium, and diode laser enucleation of prostate, yielded greater Qmax values at 6-12-months after surgery than did the resection and vaporization methods, and the difference could still be observed at 24-36 months after treatment. The advantages of the enucleation over vaporization methods were mainly observed in large prostates. Enucleation methods also achieved better IPSS than resection and vaporization methods, although the difference was not statistically significant. The new methods were generally safer than monopolar TURP. They were less likely to require patient transfusion, cause blood clot tamponade, lead to postoperative hemoglobin decline, or cause TUR syndrome.

However, the risk of short-term transient incontinence was higher in enucleation than in resection methods. Compared with resection methods, enucleation methods had more events of short-term transient urinary incontinence than resection methods. (odds ratio (OR)=1.91, 95% Confidence interval (CI); 1.35 to 2.71) Liu et al compared bipolar enucleation with bipolar TURP and found that after Foley removal, the incontinence rate was higher in enucleation than in resection at 24 hours (35.6 % vs 18.9%, p<0.01) and one week (20% vs 7.8%, p<0.05).28 There was no difference after two weeks postoperatively (3.3% vs 2.2 % at 2 weeks).

Xu et al retrospectively reviewed 1288 patient receiving bipolar enucleation and found that older age and large prostate volume were associated with postoperative stress urinary incontinence. Besides, operation time and blood loss were also reported as risk factors.

Hence many authors used modified methods such as upside down, apical preservation methods, defining the limits of dissection proximal to external sphincter prior to enucleation, in order to reduce postoperative urinary incontinence. Besides pelvic floor exercise was demonstrated to shorten the periods of stress urinary incontinence. However, the role of pelvic floor exercise in enucleation methods in BPH patients are unclear. These questions need further investigations.

6、study aim： To investigate the risk factors of transient incontinence and establish model to predict the incontinence. Besides we will evaluate different surgical methods and treatment methods to improve transient incontinence and the long-term results of different enucleation methods.

7、material and methods： I. study design: prospective cohort study II. . We plan to invite 300 patients whom received enucleation (laser or bipolar) surgery for BPH during 2020 march to 2022 march in National Taiwan University Hospital yun-lin branch to participate this study. We adopted usual care and collect patient's preoperative, intraoperative and postoperative data. The preoperative data include age, comorbidities, medication history, urodynamic parameters and urinary questionnaire. Intraoperative data include operative methods, operative time and surgical complications. Postoperative parameters include urinary questionnaire such as International Consultation on Incontinence Questionnaire-Urinary Incontinence Short Form (ICIQ-SF), 4-time use pad questionnaire, IPSS, 7-item Overactive Bladder Symptom Score (OABSS) and urodynamic parameters.

III. Outcome measure

1. Maximum urinary flow rate (Qmax) Prostate volume (TRUSP) , post-voiding residual urine (PVR ) at baseline, 3, 6, 12, and 24-month follow-up visits, pressure-flow study at baseline if indicated.
2. If incontinence and using pad, then biofeedback, ICIQ-SF, 4-item use pad questionnaire every week until incontinence cured. and different type of urinary incontinence such as stress UI, urge UI, total incontinence, mixed incontinence et al
3. IPSS, OABSS instruments, flow, TRUSP and PVR will be scored per instructions for each instrument collected at baseline and at baseline, 3, 6, 12, and 24-month follow-up visits
4. Pre-operative parameters: Age, BMI, comorbidities (DM, Hypertension, heart disease, neurologic disease), anal tone (DRESS), PSA
5. Op parameters: op methods (original en blcok or anterioposterio dissection, preserve 11-1 ocolock) enucleation and morcellation time， catheterization duration,
6. Complication: using modified clavien-dindo classification grade 1-4