Classically, mid-urethral slings have been the most widely used surgical treatment for female stress urinary incontinence (SUI). However, in recent years, concern has been raised regarding the safety and long-term complications of such procedures, such as chronic pain, vaginal or bladder erosions or urethral obstruction. In this scenario, urethral injection of bulking agents has raised interest as an alternative treatment for SUI, particularly in patients who prefer a low-risk surgical procedure, elderly patients, or those who failed after a previous anti-incontinence procedure. Although short-term efficacy has been demonstrated, current evidence does not establish long-term efficacy.
The present study aims to evaluate the medium-term results and safety for Bulkamid® in patients with SUI or mixed UI (MUI) at a tertiary center.

This retrospective observational study included patients treated between January 2019 and May 2022. Inclusion criteria included female patients 18 years or older who suffered from SUI or MUI with predominantly stress urinary incontinence treated with Bulkamid® injection. The results were evaluated subjectively with the PGI-I (Patient Global Impression of Improvement) questionnaire and the Likert scale, and objectively in the physical examination (cough test). Subjective success was considered responses 1+2 in PGI-I, whereas responders were considered responses 1+2+3 in PGI-I. 
A descriptive analysis of the data was performed using absolute frequency and percentage for qualitative variables and mean (standard deviation) or median (interquartile range) according to normality for quantitative variables. Shapiro-Wilk tests of normality were performed.

Twenty-one patients were included in our study. The mean age of the included patients was 69.7 years (14.4), with a mean BMI 30.7 kg/m2 (6.2). 2 (9.5%) patients had a personal background of pelvic radiotherapy. 8 patients (38.1%) had previously undergone an anti-incontinence intervention (4 patients had a previous transobturator tape done, and another 4 patients had both a transobturator and suprapubic vaginal tape). 
All patients presented a predominant SUI which was observed during the physical examination. In addition, 12 (57.1%) patients had an urge incontinence component. 
No intraoperative or postoperative complications were reported. After a median follow-up of 10 months (8-16.5), 8 (38.1%) patients showed no SUI, 100% being much/very much better (PGI-I). In 9 (42.9%) patients some degree of SUI persisted, of which 3 were dissatisfied, 5 satisfied and 1 neutral (Likert). 4 (19%) patients had recurrent SUI, one of them during current pregnancy; two other patients reported being satisfied with occasional leakage. Subjective success after a single injection was 32.9% and 61.5% of the patients were considered responders. 
3 patients (14.2%) underwent a second injection of Bulkamid®; 100% of them are dry and very much/much better (PGI-I).
Considering the total number of patients after 1 or 2 Bulkamid® injections, 11 (52.4%) patients have no SUI, and 18 (85.7%) patients are satisfied or very satisfied. According to PGI-I (19 patients), and considering reinjections, subjective success was 63.2%, and 89.5% of the patients were responders.

The results of the present study show that, although most patients are not completely dry, more than 80% respond to the therapy and are satisfied with the treatment (1, 2).  
According to EAU guidelines, urethral bulking agents are grated a strong recommendation to women with SUI who request a low-risk procedure (3). Although our sample is small (21 patients) compared to other studies, the patients who underwent urethral injection of bulking agent in our study showed no intraoperative or perioperative complications, being a safe procedure as indicated by current evidence and a good alternative in groups of patients who do not want complex surgery, such as elderly patients, young women with unfulfilled reproductive desire or patients with high BMI.

Bulkamid® urethral injection shows adequate objective and subjective success rates in the medium term, being a good alternative for patients with SUI seeking a minimally invasive treatment with minimal complications.

Lose G, Mouritsen L, Nielsen JB. A new bulking agent (polyacrylamide hydrogel) for treating stress urinary incontinence in women. BJU international. Jul 2006;98(1):100-4. doi:10.1111/j.1464-410X.2006.06205.x
Leone Roberti Maggiore U, Alessandri F, Medica M, Gabelli M, Venturini PL, Ferrero S. Outpatient periurethral injections of polyacrylamide hydrogel for the treatment of female stress urinary incontinence: effectiveness and safety. Archives of gynecology and obstetrics. Jul 2013;288(1):131-7. doi:10.1007/s00404-013-2718-y
Nambiar AK, Arlandis S, Bø K, et al. European Association of Urology Guidelines on the Diagnosis and Management of Female Non-neurogenic Lower Urinary Tract Symptoms. Part 1: Diagnostics, Overactive Bladder, Stress Urinary Incontinence, and Mixed Urinary Incontinence. European urology. Jul 2022;82(1):49-59. doi:10.1016/j.eururo.2022.01.045