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Bulkamid — Polyacrylamide Hydrogel

Bulkamid, now part of Boston Scientific's product portfolio, is a permanent, nonparticulate hydrogel containing 2.5% cross-linked polyacrylamide and 97.5% water. It improves urethral coaptation through submucosal volume augmentation. The US indication is SUI due to intrinsic sphincter deficiency in adult women with SUI or stress-predominant mixed incontinence; FDA approval was January 28, 2020.[1][2][3]

This is the material and device hub. For evaluation, injection workflow and follow-up, see Urethral Bulking Agents.

Role in Shared Decision-Making​

Bulking can suit women who prioritize a less invasive procedure and shorter recovery, including selected women with persistent SUI after previous continence surgery. Counsel about lower cure rates than a sling and the frequent need for repeat treatment. The 2023 AUA/SUFU guideline does not establish one injectable as superior to another. Its report of PAHG benefit persisting to 96 months is evidence of possible durability, not a guaranteed duration or a head-to-head ranking.[4]

Age, leakage severity and urethral mobility may influence outcomes, but exploratory predictors are not universal selection rules. The frequently quoted 90% response in older women with milder leakage came from a post hoc analysis combining PAHG and collagen recipients, not a validated Bulkamid-only prediction model.[5]

Future pregnancy is not an established reason to call someone an ideal candidate: the effect of treatment on pregnancy/delivery and the effect of pregnancy on treatment remain unknown. Discuss these uncertainties with women who have not completed childbearing.[2]

Labeling and Safety​

Acute UTI is a contraindication. Assess for damaged urethral tissue and correct urethral or bladder-neck stricture before treatment. Overcorrection can cause obstruction. Do not inject intravascularly; vascular occlusion and embolism are possible. Stop injection if superficial mucosal capillaries fade, because this can indicate ischemia.[2]

A homogeneous, nonparticulate composition does not eliminate every migration, erosion, granuloma or vascular complication. The FDA labeling distinguishes events observed in the pivotal study from complications reported with other bulking agents that may also occur with Bulkamid. Absence of an event in a study is not proof that its risk is zero.[3]

Other considerations include bleeding risk, impaired emptying, infection elsewhere, immunosuppression and tissue quality. The US label identifies populations in which safety/effectiveness are not established, including neurogenic bladder, predominant urgency incontinence, detrusor overactivity, specified urethral hypermobility and higher-grade prolapse. These labeling limitations should not be silently converted either into evidence of safety or into a new universal guideline prohibition.[2]

Do not mix the hydrogel with other substances or inject it into a site previously treated with a different bulking agent. The gel kit is single-patient use; the separate cystoscope has its own processing instructions. The current US cystoscope warning specifically prohibits contact of patients with a bladder-cancer history with devices disinfected using Cidex OPA.[2]

Administration Boundaries​

Injection uses endoscopic visualization and a dedicated sheath/needle system. Local anesthesia and an outpatient setting are feasible, but are not requirements for every patient. Confirm infection status, the antimicrobial plan and the ability to empty the bladder after treatment.[3]

The FDA-posted 2020 physician instructions specify a maximum 2 mL per session, top-up no earlier than four weeks, and evidence for up to three treatment sessions. These are not instructions to administer three sessions automatically. Use the current supplied IFU for exact positioning, injection plane, equipment and discharge criteria; avoid a universal per-site volume that could exceed the total limit.[3]

Main Comparative Evidence​

North American Pivotal Trial — Comparison With Collagen​

The FDA analysis included 228 Bulkamid and 117 collagen recipients. At 12 months, its composite endpoint of at least 50% reduction in both pad-test leakage and daily incontinence episodes was met by 107/228 (46.9%) versus 50/117 (42.7%), using the specified intention-to-treat analysis with last observation carried forward. Bulkamid met the trial's noninferiority criterion. This comparison was against Contigen collagen, not a sling; the original journal report used somewhat different reported analysis figures.[3][6]

Repeat treatment was common: 176/228 received two or three injection sessions. In the FDA clinical data, treatment-related acute retention occurred in 13/228 (5.7%), implant-site pain in 28/228 (12.3%) and UTI in 8/228 (3.5%). One serious hematuria event was considered probably procedure-related. These are study-specific rates, not ceilings on complications in practice.[3]

Helsinki Randomized Trial — Five-Year TVT Comparison​

The 2025 follow-up provides a long-term randomized comparison with a retropubic tension-free vaginal tape (TVT). 223 women were randomized, 212 received treatment as assigned and 195 attended at five years—92% of those treated, rather than 92% of everyone randomized.[7]

Five-year outcomePAHGTVT
Satisfaction score at least 80/10074/99 (74.7%)89/96 (92.7%)
Median satisfaction score9098
Peri-/postoperative complication before crossover22/99 (22.2%)42/96 (43.8%)

PAHG did not meet the prespecified 20-percentage-point noninferiority margin for satisfaction: the between-group difference was 18.0 points, with a 95% CI of 7.7–28.0. The complication outcome included events before crossover and is not interchangeable with serious complications, mesh exposure or reoperation. High satisfaction in many PAHG recipients can coexist with better average efficacy after TVT.[7]

Stress-test negativity, combined objective cure and patient-reported improvement are different endpoints. In the three-year publication, the cough stress test alone was negative in 78.1% after PAHG versus 95.7% after TVT.[8]

Retreatment and Previous Sling Surgery​

In a Finnish observational cohort of 391 primary procedures, two-year retreatment was 27.0% after PAHG versus 0.9% after TVT. PAHG complications in that cohort were grades I–II, but this does not establish that higher-grade complications can never occur. Patient choice, selection and local practice limit causal comparison.[9]

A systematic review after failed midurethral sling reported a pooled 80% cure/improvement estimate for the Bulkamid subgroup. “Cure or improvement” is broader than dryness, and heterogeneous small studies do not establish the optimal salvage procedure.[10]

Office-based delivery can improve cost-effectiveness, but the often-cited 58% office-use threshold comes from a particular economic model. It is not a universal local cost threshold or evidence that every patient should prefer bulking.[11]

Male Use and Pediatric Reflux​

The current US Bulkamid label warns not to use it in male patients. Older reports about other bulking materials after prostatectomy do not establish a Bulkamid indication or override that warning. More broadly, AUA/GURS/SUFU advises that efficacy is low and cure is rare with bulking for incontinence after prostate treatment.[2][12]

PAHG has been studied for pediatric vesicoureteral reflux, including a small uncontrolled series. This is outside the US Bulkamid indication; its comparison with historical dextranomer/HA results does not establish equivalence or routine pediatric eligibility.[13][2]

See also: Macroplastique, Coaptite, Durasphere.

References​

1. Boston Scientific. Bulkamid Urethral Bulking System. Current US product identity and specifications. Product resource.

2. Boston Scientific. Bulkamid Urethral Bulking System and Cystoscope: US indications, safety and warnings. Brief summary referencing IFU 110-0303rB. Current US safety information.

3. FDA. Bulkamid Urethral Bulking System: Instructions for Use. Original US approval labeling, January 2020, 10078-001. Physician labeling; PMA record and supplements.

4. Kobashi KC, Vasavada S, Bloschichak A, et al. Updates to Surgical Treatment of Female Stress Urinary Incontinence (SUI): AUA/SUFU Guideline (2023). The Journal of Urology. 2023;209(6):1091-1098. doi:10.1097/JU.0000000000003435

5. Elmelund M, Sokol ER, Karram MM, Dmochowski R, Klarskov N. Patient Characteristics That May Influence the Effect of Urethral Injection Therapy for Female Stress Urinary Incontinence. The Journal of Urology. 2019;202(1):125-131. doi:10.1097/JU.0000000000000176

6. Sokol ER, Karram MM, Dmochowski R. Efficacy and Safety of Polyacrylamide Hydrogel for the Treatment of Female Stress Incontinence: A Randomized, Prospective, Multicenter North American Study. The Journal of Urology. 2014;192(3):843-849. doi:10.1016/j.juro.2014.03.109

7. Itkonen Freitas AM, Isaksson C, Rahkola-Soisalo P, Mentula M, Mikkola TS. Tension-Free Vaginal Tape versus Polyacrylamide Hydrogel Injection for Stress Urinary Incontinence — 5-Year Follow-Up. NEJM Evidence. 2025;4(5):EVIDoa2400216. doi:10.1056/EVIDoa2400216

8. Itkonen Freitas AM, Isaksson C, Rahkola-Soisalo P, et al. Tension-Free Vaginal Tape and Polyacrylamide Hydrogel Injection for Primary Stress Urinary Incontinence: 3-Year Followup From a Randomized Clinical Trial. The Journal of Urology. 2022;208(3):658-667. doi:10.1097/JU.0000000000002720

9. Särkilahti L, Isaksson C, Mikkola TS. Tension-Free Vaginal Tape Versus Polyacrylamide Hydrogel Bulking Agent for Stress Urinary Incontinence: Patient Choice and Outcomes in Finland. International Urogynecology Journal. 2025;36(4):895-902. doi:10.1007/s00192-025-06119-9

10. Braga A, Caccia G, Papadia A, et al. Urethral Bulking Agents for the Treatment of Recurrent Stress Urinary Incontinence: A Systematic Review and Meta-Analysis. Maturitas. 2022;163:28-37. doi:10.1016/j.maturitas.2022.05.007

11. Chang OH, Shepherd JP, Cadish LA, et al. Urethral Bulking With Polyacrylamide Hydrogel Compared With Other Treatments for Stress Urinary Incontinence: A Cost-Effectiveness Analysis. Obstetrics and Gynecology. 2024;143(3):428-430. doi:10.1097/AOG.0000000000005503

12. AUA/GURS/SUFU. Incontinence After Prostate Treatment Guideline, amended 2024. Statement 25. Official guideline.

13. Ramsay S, Blais AS, Morin F, et al. Polyacrylamide Hydrogel as a Bulking Agent for the Endoscopic Treatment of Vesicoureteral Reflux: Long-Term Results and Safety. The Journal of Urology. 2017;197(3 Pt 2):963-967. doi:10.1016/j.juro.2016.08.093