Hypothesis / aims of study
As safety concerns about mesh continence procedures have grown, there has been renewed interest in urethral bulking agents, despite a paucity of adequate comparative data. Polyacrylamide hydrogel (Bulkamid) is a urethral bulking agent for treatment of stress urinary incontinence, which can be injected into the urethral submucosa under cystoscopic control. The only randomised trial suggests that Bulkamid is non-inferior to the previously available Contigen collagen bulking agent , with published observational studies suggesting that for a majority of patients, stress incontinence is cured or improved at 12 month follow up . Little is known about the impact of Bulkamid therapy on storage or voiding symptoms, or on other incontinence symptoms. Furthermore little is understood about which patient or procedural factors influence the success of the treatment. In this study we tested the impact of a single Bulkamid procedure on a range of lower urinary tract symptoms (LUTS) at 12 week follow up, and explored risk factors for treatment failure.
Study design, materials and methods
Women with symptomatic stress urinary incontinence gave written informed consent for recruitment to a prospective observational study. Before and 12 weeks following treatment women completed the validated 12 item ICIQ-FLUTS symptom questionnaire including ratings of symptom frequency and associated bother. Following treatment women additionally completed the validated Patient Global Impression of Improvement (PGI-I) scale. We systematically recorded complications, and collected surgeons' own ratings of the success of each procedure in achieving mucosal apposition. The Wilcoxon signed rank test was used to assess symptom changes, with logistic regression models used to test predictors of treatment failure.
34 women were recruited between January 2016 and November 2018, and completed follow up. The mean age was 52.1, with a median parity of 2. Urodynamically proven stress incontinence was not a mandatory inclusion criterion for surgery, but 18 women (53%) did have isolated urodynamic stress incontinence, while 9 women (26.5%) had urodynamic mixed incontinence. Patients reported relatively severe subjective stress incontinence (modal stress incontinence frequency = "all of the time" and modal symptom bother = 10 out of 10). All procedures were performed using general anaesthetic, with 2ml of polyacrylamide hydrogel injected in four deposits, 0.5–1 cm from the bladder neck using a 23-gauge needle. No patient experienced complete cure. A majority of patients (58.1%) reported subjective improvement in incontinence at 12 week follow up using the PGI-I instrument, however comparing ICIQ stress incontinence ratings a minority of women (46.4%) reported any improvement in the frequency of stress incontinence episodes, and a minority (42.8%) reported any reduction in associated bother. There were no statistically significant changes in any storage or voiding symptom (see table), but significant improvements in all incontinence symptoms and bladder pain. In multivariate regression, neither demographic factors, baseline symptom severity, nor urodynamic diagnoses were associated with treatment failure, although point estimates of the effect of surgeons' ratings of mucosal apposition were consistent with this as an appropriate way to judge intra-operative success (OR 2.96 p=0.34). There were no complications recorded, with no women requiring even temporary catheterisation.
Interpretation of results
In this observational cohort, a single treatment with Bulkamid produced statistically significant, but clinically mediocre results. No patients were cured, and a minority experienced even marginal improvement in stress incontinence symptoms. There were however, no deleterious impacts on other LUTS, and no complications. Given the poor response rate and high costs, it would be useful to understand which patients are more likely to do well with this procedure, but we did not identify significant prognostic factors. Our results may have been biased by relatively severe baseline severity, or by response biases typical of observational research.
In this observational cohort study, Bulkamid urethral bulking was associated with modest improvement in stress incontinence, and other incontinence symptoms for a minority of women, with most patients experiencing either no change or a deterioration in symptoms at 12 weeks following the procedure. Despite a poor response rate, the balance of safety and efficacy may still mean it is a reasonable first choice for some women. Further blinded studies are needed to explore when and if a second procedure is of benefit, and how Bulkamid compares to other continence procedures in medium to long term follow up.