The Role of Anterior Bladder Flap Neourethra (ABFN) in Early Urinary Continence after Laparoscopic Radical Prostatectomy The Anterior Bladder Flap Neourethra (ABFN) in RP

Purpose To evaluate the impact of anterior bladder ap neourethra (ABFN) technique on early urinary continence after laparoscopic radical prostatectomy(RP). Forty patients who underwent laparoscopic to were prospectively randomized into two groups: the ABFN group (n = 20) and the control group (n = 20). We compared continence rates and ICIQ-SF at 1d, 30 90 d and 180 d after catheter removal. In addition, the urethral pressure of two groups, the and of in the were at after catheter removal.


Results
The ABFN group had marked improvement incontinence rates at 1d, 30d and 90d after catheter removal vs the control group, while had the nearly same continence rate at 180 d. ICIQ-SF scores of the ABFN group were lower than the control group. Maximal urethral pressure (MUP), functional urethral length (FUL) and functional urethral area (UFA) for the ABFN group has signi cantly improvement than the control group. MRI showed that the neourethral length of the ABFN group was 13.7-16.2 mm, the thickness was 3.6-5.2 mm.

Conclusions
The ABFN technique markedly improved the early continence rate after laparoscopic RP.

Background
Early incontinence rates are as high as 26-93% in the rst Mon and 19-85% in the third Mon after the standard radical prostatectomy (RP), dramatically impacting the patient's quality of life [1][2][3][4] . Multiple surgical techniques aimed to improve post-RP early continence rate, for instance, methods with preservation of membranous urethra 5,6 , bladder neck 7 , Retzius space 8 , puboprostatic ligaments 9 , endopelvic fascia 10 , apical complex and lateral prostatic fascia 11 , and also techniques with the reconstruction of posterior reconstruction of rhabdomyosphincter 12 , periurethral suspension stitch 13 , anterior reconstruction 14 , anterior suspension and posterior reconstruction 2 , total anatomical reconstruction 15 . Although many patients had bene ted from the above techniques, the effect is still uncertain and unreproducible 16 . For example, continence rates one month after RP with posterior reconstruction technique were 8.2%-82.6% [16][17][18][19] . In addition, some methods had a risk of positive surgical margin (PSM) 20,21 .
This study presented an improved surgical technique, anterior bladder ap neourethra (ABFN), to form a functional neourethra to achieve high continence rates in the early post-RP period.

Study Population and Design
We prospectively analyzed 40 patients (average age 73.1 ±3.2 years) with localized prostate cancer from January 2019 to January 2021 and randomly divided them into two groups. Twenty patients in the control group underwent standard laparoscopic RP, and the other 20 patients underwent laparoscopic RP with ABFN. Age, BMI, PSA, prostate volume, IPSS score, biopsy Gleason score, clinical T stage, risk assessment CAPRA score, previous benign prostatic hyperplasia (BPH) surgery and neoadjuvant hormone therapy were recorded and compared Table 1 . Lung CT, abdominal ultrasound, pelvic MRI, and bone scan were conducted in all patients to exclude tumour metastasis. All patients were informed of the detailed surgical plan and possible risks before surgery and signed the informed consent. All methods were carried out in accordance with relevant guidelines and regulations. This study protocol was approved by the Research Ethics Committee of Jiangsu Taizhou People's Hospital.

Surgical Technique
All operations were performed by a team in transperitoneal access with ve trocars distributed as a fan.
The control group: After standard laparoscopic prostatectomy, bladder outlet and urethra were directly anastomosed. The wide bladder outlet was narrowed by suturing the posterior wall longitudinally before anastomose.
The ABFN group: After standard laparoscopic prostatectomy, the bladder outlet was trimmed into a wide circle (Fig. 1A). An area approximately 15 mm wide was selected from the anterior bladder neck between 5 and 7 o'clock. A longitudinal incision of about 15 mm was made vertically on both sides to form a lingual bladder ap (Fig. 1B). The bladder outlet was closed using 3-0 barbed sutures in a continuous longitudinal pattern from 12 o'clock to the base of the lingual bladder ap (Fig. 1C). Longitudinal sutures were applied to both margins of the bladder ap, and a tubular neourethra was formed approximately 15 mm in length (Fig. 1C). The suture was inserted at a distance of 3 mm from the incision margin and was discharged from the mucosal edge of the bladder so that the mucosa and muscle layer of the bladder were tightly aligned. Neourethra was then anastomosed to the distal urethra (Fig. 1D). The detailed surgical method can refer to the supplementary video.

Follow Up
Concerning early urinary continence, follow up was at 1d, 30 d, 90 d, 180 d after catheter removal in the outpatient department. Postoperative urinary control data were collected for all patients by January 2021. The patients were given the ICIQ-SF questionnaire. We de ned Urinary continence as no pad or one safety pad. One week after catheter removal, we detected MUP, FUL and UFA of patients in the two groups, respectively. We performed an MRI examination to measure the distance, thickness and closure condition of the neourethra.

Statistical Analysis
Categorical variables were presented as percentages, while continuous variables were presented as mean and standard deviation or median and interquartile range. SPSS 25.0 software was used to perform independent samples x 2 test, t-test, or Wilcoxon rank-sum test of the data. The difference was statistically signi cant when a p-value is <0.05.

Patient and Tumor Characteristics
There were no signi cant differences in age, BMI, PSA, prostate volume, IPSS score, biopsy Gleason score, clinical T stage, risk assessment CAPRA score, previous BPH surgery and neoadjuvant hormone therapy between the two groups, respectively (Table 1).

Perioperative and Pathological Outcomes
Operative times (p=0.191) and estimated blood loss (p=0.964) were similar in the control and ABFN groups. There were no anastomotic urine leakage and anastomotic stricture in the two groups.
Pathological characteristics in terms of stage, Gleason score, PSM rates were similar between the two groups. PSM rates were 15.00% in both groups (p =1.000) ( Table 2).

Continence Date
The ABFN group had marked improvement in continence rates at 1d, 30 d and 90 d after catheter removal vs the control group (100% vs 5%, 100% vs 10%, p 0.001 and 100% vs 60%, p=0.006) , while had the nearly same continence rate at 180 d (100% vs 95%, p=1.000). The urinary continence rates of the ABFN group were 100% at different time spots (Table 3). Only two patients used a safety pad per day in 1-2 weeks after catheter removal. ICIQ-SF scores of the ABFN group were lower than the control group at 1d   (Table 5). FUL in the ABFN group showed dual peak patterns, while the control group showed a single peak in urethral membrane pressure ( Fig. 2A, 2B).

MRI of ABFN
The length and thickness of the neourethra were measured in the sagittal plane of the urethra MRI as 13.7-16.2 mm and 3.6-5.2 mm. The neourethra was narrow and long, with no urine lling (Fig. 3A, 3B), and the neourethral lumen in the cross-sectional plane was petal-shaped and tightly closed (Fig. 3C).

Other
One patient in the ABFN group had di culty urinating one day after removing the urethral catheter, which was relieved one week after retaining the urethral catheter. One patient in the control group had di culty urinating two weeks after removing the urethral catheter and failed to place catheter. Urethroscopy revealed vesicourethral anastomotic stricture, which was relieved by giving two weekly dilations. All other patients in both groups voided freely and had no residual urine.

Discussion
The mechanism of incontinence in the early post-RP period (within three mons) is still unclear 16 . Still, many researchers have recognized the critical role of FUL in urinary continence 16 , and preserving bladder neck and apex urethra can maintain FUL and improve continence in the early post-RP period 5,7,21 .
However, the prostate protruded at the apex. The bladder neck often squeezes the urethra and bladder neck and resulted in the inability to preserve these tissues with su cient thickness and length.
Meanwhile, maintaining the apex urethra and bladder neck has a risk of PSM at both ends of the prostate 20,21 .
More researchers also have recently recognized the function of FUL in RP is a signi cant cause of postoperative incontinence 5,7,22 . From the aspect of urodynamics, higher intraurethral pressure than intravesical pressure is essential, and FUL is the determining factor for urinary continence. According to the laws of uid dynamics, urethral resistance and FUL are directly proportional to each other. Therefore, when FUL becomes shorter, it will reduce the ability of the urethra in continence. In addition, the urethra is an elastic tubular tissue that closes under abdominal pressure. When FUL is signi cantly shortened, the abdominal pressure on the urethra decreases, which reduces the ability of the urethra in continence.
ABFN forms a neourethra with speci c length and thickness, which theoretically can increase FUL and improve urinary continence in the early postoperative period. However, ABFN conducted by Steiner in1993 with a continence rate of only 55% in the third-month post-RP has no signi cant advantage over other current techniques 23 . Steiner found by cystography that the funnel-shaped bladder neck was lled with contrast medium in the early postoperative period. According to the laws of uid dynamics, urethral resistance is inversely proportional to the urethral diameter. Therefore, we believe that Steiner cut the bladder outlet at 10 and 2 o'clock. As a result, the anterior bladder ap was too broad, resulting in a neourethra with an apparent funnel shape, which could not form a well-closed functional urethra.
Unfortunately, since Steiner did not perform a functional analysis, such as urethral manometry, it was not possible to understand the functional status of the neourethra. In addition, since the surgery approach has been proved to be one of the factors affecting urinary continence 24 , the open surgery performed by Steiner may be one of the possible reasons for the low urinary continence rate.
Based on Steiner's work, we made a vertical incision in the anterior bladder wall at 5 and 7 o'clock of the bladder outlet and took a bladder ap about 15 mm wide and 15 mm long for curling and suturing to form a narrow, tubular neourethra. MRI showed narrow and long neourethras with su cient thickness and good static closure shape. The functional urodynamic test revealed that the pressure of the neourethra formed the rst peak of the pressure curve (Fig. 2B). The increased MUP and FUL signi cantly improved UFA in the ABFN group. As a result of the fact that ABFN had reconstructed FUL in morphology and function, all of the patients in the ABFN group achieved immediate urinary continence from the catheter removal.
ABFN does not require preservation of the structures and tissues surrounding the urethra and prostate, nor does it require deliberate protection of bladder neck or maximal urethra length. Thus, it avoids the PSM risk and the di culty of the above preservation techniques and can be applied in all organ-con ned prostate cancer cases. Furthermore, because the operation of the ABFN technique is simple and the diameter and length of the ABFN are relatively constant, ABFN does not increase the operation time and blood loss, which can be completed by any doctor who masters the standard laparoscopic technique. In addition, since ABFN is made of the bladder wall, its blood supply is abundant, and its edges heal well, avoiding neourethral luminal strictures and urinary stulas.
Despite the prospective randomized study design, the limitations of this study included the small sample size, the lack of comparisons with other techniques, and the single-center setting.

Conclusions
In summary, ABFN showed a signi cantly better early continence rate than standard RP, an effective, safe and reproducible technique to improve the early continence rate. More de nitive results would require further clinical studies with large numbers of cases.

Declarations
Funding No funding source was associated with this study.
Declarations of interest: There are no nancial con icts of interest to disclose.
Data availability: Not applicable.