Rigi10™ Malleable Penile Prosthesis
Also Known As
Periurethral bulking agents, urethral injectables, injectable urethral bulking materials, periurethral injectables, urethral bulking therapy, injectable agents for stress urinary incontinence, periurethral injection therapy
Definition
Urethral bulking agents are injectable substances used to treat stress urinary incontinence by increasing urethral resistance and improving urethral mucosal coaptation. These minimally invasive treatments involve injecting biocompatible materials into the submucosal tissues of the urethra to artificially inflate the urethral wall, thereby narrowing the urethral lumen and preventing involuntary leakage of urine during physical activities that increase abdominal pressure1. The bulking effect increases outlet resistance and restores the mucosal seal mechanism of continence2. The ideal bulking agent should be non-resorbable, nonimmunogenic, nonallergenic, and biocompatible to reduce the risk of inflammation and fibrosis3. Various materials have been developed and used as urethral bulking agents, including polyacrylamide hydrogel, calcium hydroxylapatite, polydimethylsilaxone, and previously, glutaraldehyde cross-linked bovine collagen4. These agents can be injected either transurethrally or periurethrally, typically at multiple sites around the urethra approximately 0.5-1.0 cm distal to the bladder neck5.
Clinical Context
Urethral bulking agents are primarily used in the clinical management of stress urinary incontinence (SUI) or stress-predominant mixed urinary incontinence (MUI), particularly in women with intrinsic sphincter deficiency1. These treatments fill an important need in the therapeutic armamentarium against SUI, serving patients who are not candidates for more invasive surgical interventions and those with multiple prior failed anti-incontinence procedures2. The procedure is particularly suitable for patients with low to moderate volume SUI, those who desire a minimally invasive option with lower risk profile compared to surgery, and patients with specific contraindications to surgical management3.
Patient selection criteria typically include those with demonstrated stress urinary incontinence, particularly those with intrinsic sphincter deficiency rather than urethral hypermobility4. Ideal candidates include elderly patients with high anesthetic risk, those unable to interrupt anticoagulation, young patients who may desire future pregnancy, and patients with a combination of SUI and poor bladder emptying5. Contraindications include active urinary tract infection and hypersensitivity to the bulking agent6.
The surgical procedure for urethral bulking agent injection is typically performed under local anesthesia in an outpatient setting, with minimal recovery time. The technique involves transurethral or periurethral injection with endoscopic visualization, commonly using a three-point injection plan at 2, 6, and 10 o’clock positions, with material placed 0.5-1 cm distal to the bladder neck7. The volume injected at each site ranges from 0.2-0.8 ml, with the goal of visually reaching the midline of the urethra8.
Clinical outcomes show that urethral bulking agents have modest efficacy compared to more invasive surgical options, with studies reporting 53-67% of patients feeling cured or improved after treatment9. However, repeat injections are often required to maintain efficacy, with studies showing that up to 77% of patients may need additional treatments10. Long-term follow-up studies demonstrate durability of effect in properly selected patients, with one 7-year study showing 67.1% of patients reporting feeling cured or improved when the bulking agent was used as a primary procedure11. Potential complications include transient urinary retention (reported in 15.3% of patients), urinary tract infection (3.5%), hematuria, de novo urgency incontinence, and rare cases of bulking agent extrusion or granuloma formation12.