Maintaining Bilateral Arterial Catheters to Achieve Delayed Endpoint Embolization in Uterine Artery Embolization and Prostatic Artery Embolization: A Technical Perspective.

This technical note has no impact on patient care; therefore, Institutional Review Board approval was waived. Written informed consent was obtained from each patient before the procedure. All manuscript preparation processes complied with the Declaration of Helsinki.

Irrespective of the embolization procedure, delayed angiographic reassessment consistently demonstrated renewed forward flow in territories previously deemed complete based on conventional stasis at five cardiac cycles. This facilitated additional flow-directed embolization in every case, often significantly, enabling a physiologically driven, delayed endpoint and denser particle deposition. The use of single- or dual-operator workflows allowed for alternating particle delivery from both sides, maintaining procedural efficiency. Between 2014 and 2024, 140 patients underwent UAE and 50 patients underwent PAE via bilateral femoral access. The safety, clinical, and technical outcomes of dual access are summarized in Table 1 . UAE symptom improvement was defined by ≥10-point Uterine Fibroid Symptom Health-Related Quality of Life Questionnaire (UFS-QOL) symptom severity reduction or ≥20-point QoL improvement. The mean fibroid infarction rate following UAE was 97%. Symptomatic improvement was assessed using the UFS-QOL score. Over 10 years, no incidence of uterine necrosis, endometritis, cervical or vaginal ischemia was seen. The initial experience of increased pain after UAE was improved with the routine use of SHNB in the last five years. Post-embolization syndrome after discharge was not quantified. In PAE, symptom improvement was defined by a ≥5-point IPSS reduction or a ≥1-point QoL reduction, assessed at three months, one year, and then annually up to 10 years. Among PAE cases, at five-year follow-up, the mean reduction in IPSS and QoL score was 11 and 2 points, respectively. No incidence of urethral ulcers, symptomatic rectal ulcers, or penile or perineal ischemia was seen. The contrast volume used was comparable to single-access embolization techniques. Notably, although not formally quantified, the dose-area product was consistent with previous published literature [7] . Ten-Year Safety and Technical Outcomes of Bilateral Femoral Access in UAE and PAE. PAE: prostate artery embolization; UAE: uterine artery embolization

Our institution maintains a prospectively recorded fibroid and prostate database. Due to the retrospective observational nature of this study, Institutional Review Board approval was waived, and written informed consent was obtained from all patients before the procedure. All procedures were performed under conscious sedation and local anesthesia, often with two operators who had five to 22 years of experience in embolotherapy. Bilateral common femoral artery access was obtained under ultrasound guidance, and five French (Fr) standard vascular sheaths were placed. UAE was typically performed using bilateral 5 Fr Rosch inferior mesenteric catheters (Cook Medical), advanced beyond the cervico-vaginal branches. Microcatheters (Parkway Soft; Asahi Intecc Co., Nagoya, Japan, or Progreat Alpha; Terumo Interventional Systems, Japan) with the guidewires that come along with them were used as required, depending on anatomical complexity such as ostial anatomy, vessel size, and tortuosity, and operator preference. Each vial of TAGM (2 mL) was first mixed with seven mL of contrast medium (Visipaque™ 320; GE HealthCare Ireland, manufactured in Cork, Ireland, or Omnipaque™ 300; GE Healthcare Ireland, Cork, Ireland) to create a stock suspension. From this, embolic aliquots were prepared at a final dilution of approximately 1:10 (TAGM: contrast + saline mixture) using a 1:1:1 ratio of stock, contrast, and saline, and were injected in 0.5-1 mL aliquots under fluoroscopic guidance. Embolization began with 300-500 micron TAGM (Embosphere; Merit Medical) for adenomyosis and 500-700 micron TAGM for fibroids, with escalating size based on flow dynamics and endpoint evaluation under fluoroscopy, but rarely exceeding 700-900 micron. PAE was done using bilateral five Fr Cobra catheters (Cook Medical) and any of the 1.9, 2.1, or 2.4 Fr microcatheters (Parkway Soft; Asahi Intecc Co., Nagoya, Japan, or Progreat Alpha; Terumo Interventional Systems, Japan). Embolization using 100-300 micron TAGM (Embosphere; Merit Medical) from conventional catheter positions was performed, with or without coil protection to avoid non-target embolization. Coils used most commonly were the 2 mm × 2 cm 0.018 coils (Nester Embolization Coil, Cook Medical, Bloomington, IN, USA). In our practice, cone beam CT (CBCT) was performed after selective microcatheterization of each prostatic artery with unilateral contrast injection (8-10 mL of 70:30 diluted contrast at 1 mL/sec, 8-second acquisition, 210 ° rotation). Multiplanar and MIP reconstructions were reviewed to confirm complete opacification of the target hemiprostate and to detect potential non-target branches (e.g., rectal, vesical, or penile collaterals). Coil protection was performed as indicated. The volume of embolic material injected was instead guided by CBCT and angiographic findings on each side until a delayed endpoint (≥5 cardiac cycles of stasis with reflux) was reached. Alternating slow and dilute embolic delivery from each side was standard. As one side underwent embolization, the contralateral side was allowed to redistribute particles. Bilateral catheterization allowed for resumption of embolization without re-access or recatheterization. During most cases, two standard waiting periods were used: first, during Superior hypogastric nerve block (SHNB) preparation in UAE, and second, during gelfoam slurry preparation (where applicable). These pauses served as built-in delayed reassessment points. Top-up embolization was then administered via the already-positioned catheter. Gelfoam was prepared as a slurry and delivered to the proximal trunk in all cases of UAE and in select cases of PAE as a terminal step to reduce risk of revascularization. This has been our practice over the last 10 years. We did not switch to routine radial artery access due to results obtained below. In PAE, gelfoam was used selectively in patients with large prostates (>100 cc) or significant collateral flow. These cases (quite typical of all cases) underscore the dynamic perfusion shifts that occur during pelvic embolization and suggest a role for intermittent reassessment and top-up embolization facilitated via dual femoral access. A 42-year-old woman with symptomatic fibroids (UFS score 25, QoL score 129) underwent UAE via bilateral femoral access. Pre-procedural MRI revealed an enlarged uterus (14.2 × 9.7 × 12 cm) with a dominant posterior intramural fibroid measuring 7.7 × 10.7 × 9.9 cm. No evidence of adenomyosis or endometriosis was noted. Bilateral angiography showed a predominant supply from the right uterine artery, without any utero-ovarian anastomoses. Embolization was initiated bilaterally using 500-700 micron TAGM, followed by 700-900 micron. At 20 minutes, contrast stasis over five cardiac cycles, reflux into the proximal trunk, and distal pruning were observed bilaterally, meeting conventional embolization endpoints ( Figure 1a ). At 25 minutes, after an interval to administer SHNB, repeat angiography bilaterally revealed significant renewed fibroid perfusion, particularly on the right ( Figure 1b ). Bilateral top-up embolization was then performed from the same catheter position. At least half a bottle of additional 700-900 micron TAGM was injected beyond the conventional endpoint. At 40 minutes, right-sided stasis at five cardiac cycles with reflux was achieved ( Figure 1c ). Re-embolization endpoint in UAE was defined as stasis in the renewed forward flow and residual tumor bed staining, and with a standing column of contrast in the vertical part of the uterine artery and reflux on contrast administration. Gelfoam was administered at this stage to close the trunk. The same protocol was followed for the contralateral side. The patient was monitored overnight with sedation analgesia and discharged the following day after catheter removal. At one-month follow-up, MRI demonstrated 100% fibroid infarction ( Figure 1d ) with 65% fibroid and 59% uterine volume reduction. Symptom severity and QoL scores improved to 13 and 50, respectively. The case, including pre-procedural MRI, baseline angiography, delayed endpoint assessment, final embolization sequences, and follow-up MRI, is presented in Video S1 . A 42-year-old woman with a 10 cm symptomatic fibroid (UFS-QOL symptom severity score: 25; quality of life score: 129) underwent UAE via bilateral femoral access. The complete procedure, including pre-procedural MRI, baseline angiography, delayed endpoint assessment, final embolization runs, and post-procedure MRI, is demonstrated in Video S1 . a: Ten minutes after bilateral simultaneous embolization, contrast stasis at five cardiac cycles is observed in both uterine arteries. A dense column of embolic material is visible on the right (red arrows), with near-complete pruning of distal branches bilaterally, consistent with the conventional angiographic endpoint. b: At 14 minutes, reperfusion of the fibroid vascular bed is noted bilaterally (yellow arrows), despite initial stasis, indicating potential for further embolization. c: At 40 minutes, persistent five-cardiac-cycle stasis is seen on the right. Additional embolization using Gelfoam slurry was performed. A similar delayed protocol was applied on the left side. d: Follow-up MRI at 1 month shows complete (100%) non-enhancement of the dominant fibroid on sagittal post-contrast images, consistent with infarction. Fibroid and uterine volumes had reduced by 65% and 59%, respectively. Symptom severity and QoL scores improved to 13 and 50, respectively. UAE: uterine artery embolization; UFS-QOL: Uterine Fibroid Symptom Health-Related Quality of Life Questionnaire A 71-year-old man with symptomatic benign prostatic hyperplasia underwent PAE via bilateral femoral access. Baseline parameters were: prostate volume 116 cc, serum prostate-specific antigen level of 1.0 ng/mL, International Prostate Symptom Score (IPSS) 18, and QoL score of three. Angiography confirmed appropriate catheter positioning ( Figure 2a ), and CBCT showed complete opacification of the left hemiprostate. Embolization was initiated with 100-300 micron TAGM, with coil protection of a rectal branch. At 14 minutes, angiography revealed pruning of intraprostatic vessels and the emergence of a pudendal collateral, suggesting rising intraprostatic resistance ( Figure 2b ). Embolization proceeded on the contralateral side. Despite apparent initial stasis, delayed re-look angiography on the left 45 minutes later showed significant renewed perfusion of the left prostatic bed ( Figure 2c ). Additional TAGM filling the prostatic bed was then injected without reflux. The additional amount needed for PAE was much smaller than for UAE. At 60 minutes, complete stasis was achieved at five cardiac cycles with reflux, our proposed delayed endpoint. Subsequently, Gelfoam slurry embolization of the left prostatic trunk was performed. The same protocol was followed on the contralateral side. The patient was allowed to sit up and gently mobilize three hours later and was discharged the following day after catheter removal. At 1-month follow-up, MRI demonstrated 90% infarction of bilateral transition zones ( Figure 2d ). IPSS score, QoL score, and prostate volume had reduced to 9, 2, and 98 cc, respectively. The case, including baseline angiography, delayed endpoint assessment, final embolization sequences, and follow-up MRI, is presented in Video S2 . A 71-year-old man with symptomatic BPH, prostate volume of 116 cc, IPSS of 18, and QoL score of three underwent PAE via bilateral femoral access. The full procedure, including baseline angiography, delayed endpoint assessment, final embolization sequences, and follow-up MRI, is shown in Video S2 . a: Baseline angiogram of the left prostatic artery. b: At 15 minutes, after embolisation, repeat angiography demonstrates near-complete pruning of the prostatic vascular bed. A new collateral from the pudendal artery (red arrow) is noted, likely reflecting increased resistance within the prostatic microcirculation after embolization. This collateral was absent in the baseline angiogram. c: At 45 minutes, substantial reperfusion of the prostatic vascular bed is observed (yellow arrows), on the ipsilateral side during this interval. This delayed filling highlights the importance of reassessment. Between 15 and 45 minutes, embolization of the contralateral side was performed (not shown). Further top up embolisation was done at this point. d: One-month follow-up MRI: Coronal post-contrast image reveals >90% infarction of the transition zone. Clinical parameters improved significantly, with a reduction in IPSS to 9, QoL score to 2, and prostate volume to 98 cc. IPSS: international prostate symptom score; BPH: benign prostatic hyperplasia; PAE: prostate artery embolization; QoL: quality of life

This brief report hypothesizes that bilateral femoral access can facilitate delayed embolization endpoints in UAE and PAE. By allowing delayed, intermittent reassessment whilst performing contralateral embolization, a more uniform and deeper embolic distribution and occlusion of target vasculature can be achieved, which may have clinical consequences. Perhaps it is time to rethink whether the dual access technique for pelvic embolization is truly outdated.

Bilateral femoral access for UAE or PAE is not a new technique, but the wide adoption of radial access for pelvic embolization has relegated this approach to archaic. A randomized controlled trial by Costantino et al. [7] showed that bilateral access in the UAE resulted in less fluoroscopy time, shorter procedure time, fewer angiographic images, no difference in dose-area product, and no major access-related complications compared to single access. In our experience, this approach does not incur any additional access site complication penalty, particularly with the current practice of ultrasound-guided access and the use of closure devices. The current society guidelines do not endorse a specific access route for UAE [8] or PAE [9] , leaving the decision to operator preference. The embolization endpoint is subjective, applies to all vascular beds, correlates with the degree of necrosis, and has been extensively studied in other settings such as liver chemoembolization, with implications for prognosis [10] . Cardiovascular and Interventional Radiological Society of Europe (CIRSE) guidelines [9] define the endpoint in PAE as slow flow or stasis with gland opacification, while for UAE, Society of Interventional Radiology (SIR) [8] recommends cessation once fibroid-penetrating branches are occluded even if proximal flow persists. Pelage et al. [11] initially described the conventional endpoint in UAE as absent residual fibroid hypervascularity, stasis in the distal uterine artery, and reduced flow in the proximal uterine artery. However, in our experience, a deliberate waiting period following this conventional angiographic endpoint allows flow redistribution and identification of residual perfusable territories while proceeding with contralateral embolization. The principle of distal embolic penetration is also seen with the use of liquid embolic agents such as n-butyl cyanoacrylate in PAE [12 , 13] . With our technique, we hypothesize that comparable or better distal penetration and therapeutic efficacy can also be achieved using particulate embolics [14] . Periodic waiting during vascular bed embolization is a standard elementary practice. Rapid embolic injection, on the other hand, without intermittent assessment often leads to heterogeneous infarction due to uneven particle distribution. The trickle embolization or “ stop-and-go" method described here promotes more uniform, denser, and distal particle deposition, enhancing the completeness and durability of the embolic effect. Bilateral femoral access enables this without additional procedural time penalty and provides a convenient workflow without increasing procedural morbidity. Gelfoam top-up embolization has been an integral part of embolotherapy for fibroids at our institution since its inception. We believe that this additional step has contributed to the consistently high fibroid infarction rates observed in our cohort. No comparative cohort without Gelfoam top-up is available. Bilateral femoral access may be especially beneficial in select anatomical and clinical scenarios. These include patients with large fibroid or prostate volumes, asymmetric arterial dominance, complex or tortuous pelvic arterial anatomy, and cases with prominent utero-ovarian or accessory prostatic collaterals. In such settings, single access may necessitate challenging ipsilateral catheterization of steep or angulated branches, prolonging procedure time and increasing technical difficulty. Dual access enables a more direct, contralateral approach to each iliac artery (the standard approach for unilateral iliac artery embolization), improving catheter stability and facilitating dynamic assessment of embolization endpoints without repeated re-navigation. While bilateral femoral access may seem contrary to current efforts to further minimize procedural invasiveness, the routine use of vascular closure devices and early ambulation has significantly reduced associated morbidity. The goal of minimizing invasiveness should be balanced against the potential for enhanced procedural efficacy and long-term clinical outcomes. At our institution, bilateral femoral access with delayed endpoint assessment has been the standard technique since the inception of our UAE and PAE programs, which started as a legacy from the time when dual access was performed to reduce radiation dose or procedure time. The renewed perfusion was found by serendipity, and, given the subsequent fibroid and prostate infarction proportions on imaging, the technique was not changed. A clear superiority of this approach, of course, cannot be established without a suitable control group or a direct comparison with single-access embolization. Multiple factors are known to influence recanalization and recurrent organ supply in the short or long term after embolization. These include, but are not limited to: the type of particles (PVA vs TAGM's, permanent or temporary), the size of particles, the catheter position, the speed of injection, the degree of dilution, the type of collateral flow to the fibroids (e.g., from the ovarian artery), the choice of end point (complete stasis or near-complete stasis), the nature of arterio-arterial anastomosis in the short term, and particle extrusion and neoangiogenesis in a thrombosed vessel in the long term [15 , 16] . Even in well-designed prospective studies, it is impossible to account for all the above confounding factors. In this retrospective study, therefore, we can only suggest that delayed top-up embolization may obviate some of the above factors in preventing recanalization. We believe that enhanced embolization, increased fibroid necrosis, and reduced recurrence rates may offset the additional cost incurred for extra micro catheters and closure devices, although a formal assessment of this has not been performed. Notably, our data compares favorably with prior studies using unilateral or radial access, supporting the safety and efficiency of bilateral femoral access [7 , 17 - 19] . However, this remains a limitation of this technique-oriented report on the feasibility and advantages of the dual femoral access procedure. Future comparative studies would be required to demonstrate any superiority in outcomes with pelvic embolization.

Uterine artery embolization (UAE) and Prostatic artery embolization (PAE) are established minimally invasive techniques for symptomatic uterine fibroids and benign prostatic hyperplasia (BPH), respectively, with proven efficacy in improving symptoms and quality of life (QoL) [1 , 2] . However, long-term failure rates remain problematic, with recurrence reported in up to 50% of cases, often attributed to incomplete target tissue necrosis [3] . Redistribution of embolic particles over time is common, particularly in vascular beds with multiple collateral supplies. A conventional endpoint, variously reported as 3-10 heartbeat stasis [4] , may still leave part of the vascular bed perfused after redistribution. Deeper particle penetration correlates with greater ischemic necrosis and a more durable clinical response [5] . When embolization is performed sequentially from unilateral access, increased resistance from the opposite side may prevent forward particle movement into the distal vasculature and give an earlier impression of stasis, which may reperfuse later despite an apparent angiographic endpoint [6] . This technique-focused report hypothesizes that such a limitation may be overcome by allowing the operator to perform top-up embolization using dual femoral access and catheters in the uterine or prostatic arteries, without any time penalty or increased morbidity. The technique of dual femoral access is described here with reference to the two commonly performed pelvic embolization procedures using case examples.

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Real-time uterine artery embolization procedure in a 42-year-old woman with symptomatic fibroids. The video includes pre-procedural MRI, selected angiographic sequences, delayed endpoint assessment, and follow-up MRI. Real-time prostate artery embolization in a 71-year-old man with symptomatic benign prostatic hyperplasia. The video includes baseline angiography, selected angiographic sequences, delayed endpoint assessment, and follow-up MRI.