We previously demonstrated that benign prostate hyperplasia (BPH) and erectile dysfunction (ED) could be associated with poor preoperative urethral function in men by evaluating the relationship between these factors and preoperative maximum urethral closure pressure1. Atherosclerosis and pelvic ischemia due to metabolic syndrome are involved in the pathophysiology of BPH and ED development. Therefore, we hypothesized that atherosclerosis and pelvic ischemia may be involved in the relationship between poor preoperative urethral function and BPH/ED.
This study aimed to evaluate the relationship between urethral blood flow analyzed using intraoperative indocyanine green (ICG) angiography and clinical factors such as prostate volume and erectile function, and postoperative urinary incontinence after robot-assisted radical prostatectomy (RARP).

This was a single-center prospective study that enrolled 50 consecutive male patients who underwent RARP for prostate cancer between November 2020 and February 2022. RARP was transperitoneally performed by two experienced surgeons using the da Vinci Xi system. ICG was intravenously administered at a dose of 0.15 mg/kg before resection of the urethra. The urethral blood flow was observed using the firefly fluorescence system. A quantitative analysis of ICG angiography was performed using movie analysis software (Hamamatsu Photonics K.K., Japan). Briefly, three regions of interest (ROI) were selected in the urethra, and time curves of ICG fluorescence intensity were drawn. The urethral blood flow at the three ROIs of the urethra was measured and average was calculated. To assess the validity of the intraoperative ICG angiography method, we analyzed the correlation between urethral blood flow and abdominal arterial sclerosis, which was evaluated by calculating the abdominal aorta calcification index (ACI) on computed tomography (CT). To calculate the ACI, the aorta was divided into 12 areas in each slice of the CT scan. An area with calcification was scored as 1, whereas an area without calcification was scored as 0. The total calcification score in all slices was then calculated as2: ACI = (total score for calcification in each slice)/ (12 x [the number of slices]) x 100.
In addition, we calculated the 24-hour urine loss rate immediately after urethral catheter removal, which was defined as the urinary incontinence volume divided by the voided volume added to the urinary incontinence volume. We evaluated the relationships between intraoperative urethral blood flow and the 24-hour urine loss rate, and between intraoperative urethral blood flow and the following clinical factors: age, prostate volume, International Index of Erectile Function-5 (IIEF 5) score, and nerve-sparing surgery.

Urethral blood flow was significantly negatively correlated with ACI (r = -0.479, p=0.001), demonstrating the validity of the intraoperative ICG angiography method. Moreover, urethral blood flow was significantly higher in the high IIEF 5 group (≧ 12 scores) or small prostate-volume group (< 40 mL) (p = 0.02) compared to the low IIEF 5 group (< 12 scores) or large prostate-volume group (> 40mL) (p < 0.001). However, there was no significant difference in age between the two groups. Furthermore, urethral blood flow was significantly higher in patients who underwent nerve-sparing surgery than in those who did not (p = 0.01). Moreover, there was a significant negative correlation between intraoperative urethral blood flow and the 24-hour urine loss rate (r = -0.649, p < 0.001) (Fig. 1). Multiple linear regression analysis was performed to predict urethral blood flow based on IIEF5 scores, prostate volume, and nerve-sparing surgery. A significant regression equation was found (Table1).

These results indicate that: (1) the method of our intraoperative ICG angiography is valid, as shown by a significant correlation between abdominal arterial sclerosis and urethral blood flow obtained by intraoperative ICG angiography; (2) BPH and ED are involved in poor urethral blood flow; (3) nerve-sparing surgery preserves urethral blood flow; (4) patients with high urethral blood flow have a low 24-hour urine loss rate immediately after the removal of the urethral catheter.

Urethral blood flow may be associated with arterial sclerosis and pelvic ischemia. High intraoperative urethral blood flow may facilitate early recovery from postoperative urinary incontinence after RARP.

Urodynamic evaluation before and after to RARP to identify pre and intraoperative factors affecting postoperative continence. Tsuyoshi Majima, Yoshihisa Matsukawa, Yasuhito Funahashi, Masashi Kato, Naoto Sassa, Momokazu Gotoh. Neurourol Urodyn. 2021 Jun; 40 (5): 1147-1153.
Association between pentosidine and arteriosclerosis in patients receiving hemodialysis. Takanori Kitauchi , Katsunori Yoshida, Tatsuo Yoneda, Toshihisa Saka, Motoyoshi Yoshikawa, Seiichirou Ozono, Yoshihiko Hirao. Clin Exp Nephrol (2004) 8:48–53.

Continence 2S2 (2022) 100232
DOI: 10.1016/j.cont.2022.100232