Polyacrylamide Hydrogel (PAHG), Bulkamid®, is a non particle-based urethral bulking agent that has demonstrated longer term durability compared to other bulking agents.  PAHG acquired FDA approval in 1/2020, limiting clinical outcomes data in the U.S. Prior studies demonstrated the safety, efficacy, and durability of PAHG in index patients with stress urinary incontinence (SUI).  Outcomes following PAHG injection in women with a history of mesh sling excision and/or refractory SUI are lacking.  The objective of this study is to examine short-term outcomes of PAGH injection in our initial cohort, specifically looking at women with intrinsic sphincter deficiency (ISD), post mesh sling excision, and/or refractory SUI.

Demographics, clinical characteristics, and urodynamic data were collected in women undergoing urethral bulking with PAHG at a single tertiary referral institution.  PAHG injection was performed using the standardized technique endorsed by Contura. Post-procedural assessments included the patient global impression of improvement (PGI-I), patient reported percentage improvement, overall satisfaction, Urogenital Distress Inventory (UDI-6), adverse events, and further SUI treatment, were conducted at 4-6 weeks and 3 months.

Between 5/2020 and 11/2020, 48 women were treated with PAHG. Of those, 34 completed follow up questionnaires. Seven women completed questionnaires with minimum 90 days of follow up. Mean age was 57 (SD 15) and mean BMI was 27.52 (SD 6). Among 27 women receiving PAHG as primary treatment for SUI, 10 demonstrated VLPP <60 cmH20 consistent with intrinsic sphincter deficiency (ISD). One woman had SUI previously managed with a non-PAHG bulking agent. Eleven women with a history of mesh sling excision received PAHG. Nine women had refractory SUI after prior mid-urethral sling (MUS) which was still in place at the time of PAHG injection. 

At a minimum of 4 weeks follow-up, the median percentage symptom improvement in the overall patient cohort was 85% (IQR 70-90), and median overall satisfaction on a Likert scale was 9/10 (IQR 7.25-10). The rate of bothersome SUI after PAHG identified on UDI-6 was 58.8%, the rate of bothersome difficulty emptying identified by UDI-6 was 23.5%. The rate of transient post-procedural urinary retention, defined as requiring intermittent catheterization or foley catheter placement, was 20.6%, and the rate of procedural urinary tract infection (UTI) was 5.9% (Table 1). No patient required long term foley catheterization after PAGH.

In women presenting with SUI without ISD and no prior procedures, the median percentage symptom improvement was 90% (IQR 70-90), and median overall satisfaction on a Likert scale was 9/10 (IQR 8-10). In this subset of patients, the rate of bothersome SUI after PAHG was 61.5%, and the rate of bothersome difficulty emptying was 15.4%. The rate of transient post-procedural urinary retention was 23.1%, and the rate of post-procedural (UTI) was 7.7%. 
In the subgroup of women with prior urethral procedures including those with existing slings, mesh excision, and/or ISD, the median percentage symptom improvement ranged from 70%-90%, and the median overall satisfaction on a Likert scale ranged from 8-10. The rate of persistent SUI after PAHG was 33.3%-100%. The rate of bothersome difficulty emptying the bladder ranged from 0-50%. The rate of adverse post procedural events was 16.7-33.3% for transient post-procedural urinary retention requiring intermittent catheterization, and 0-16.7% for post-procedural UTI (Table 1).

Prior studies have demonstrated the safety, efficacy, and durability of PAHG in index patients with primary SUI, however data is lacking on contemporary outcomes of PAHG in non-index patients with SUI. The results presented herein suggest short term efficacy of PAHG in non-index patients including those with ISD, those with refractory SUI and existing midurethral sling, as well as those with prior mesh excision from the urethra and/or vagina. However, median reported percentage symptom improvement and overall satisfaction is lower in those with prior mesh excision, compared to those with refractory SUI and existing slings, ISD, or those with index SUI. These results suggest that patients with a history of vaginal mesh excision may expect slightly less symptom improvement and less overall satisfaction with the results of PAHG urethral injection in the short term. 

Despite high median symptom improvement and overall satisfaction, the rate of bothersome SUI after PAHG was greater than 60% in all patient subsets except for those with ISD and no prior SUI procedure (33.3%). Of note, all patients with refractory SUI and existing midurethral sling reported bothersome SUI after PAGH urethral bulking, but patients in this subset reported the highest median percentage improvement (90%) and overall satisfaction (10/10) compared to the other subsets, including those with index SUI without ISD and no prior procedures. These results suggest that the rate of persistent bothersome SUI should not be used as a standalone evaluation of successful outcome for SUI treatment.  In addition, bothersome difficulty emptying was also relatively common, and may also be a factor in patient reported symptom improvement and overall satisfaction. 

The rate of adverse events including UTI and transient urinary retention was low for the entire patient cohort, as well as for the various subgroups, however a larger patient cohort is necessary to fully evaluate these rates.

In the subset of non-index women with SUI (ISD, refractory SUI with existing MUS, and post-mesh sling excision) treatment with PAHG achieved a median of 85% improvement, with a low rate of complications. Short term data suggests PAHG is effective in treating non-index and complex SUI patients, however longer term follow-up with a larger cohort is needed to assess the durability of these results.