Preoperative Preparation and Planning
Injectable urethral bulking agents are a minimally invasive treatment option for stress urinary incontinence (SUI). Bulking agents aim to restore continence by increasing urethral resistance at rest, while still allowing the urethra to open during micturition. For patients with isolated intrinsic sphincteric deficiency (abdominal leak point pressure [ALPP] <100 cmH 2 0) with minimal hypermobility of the proximal urethra and bladder neck (15 degrees descensus or less) who cannot undergo or do not wish to undergo an invasive surgical treatment for SUI, bulking agents are a reasonable treatment option. Patients should be counseled that both efficacy and result durability are potentially inferior to those of traditional surgical options, and multiple injection procedures can often be required to achieve a desirable effect. It has been shown that bulking agent injections can result in an improvement in incontinence, but patients may not necessarily achieve dryness. Most clinical studies report modest efficacy over a short duration of up to 75% improvement or cure and show substantially less improvement at 1 year. Nevertheless, bulking agents can be quite effective in the properly selected patient and can be performed either as an office-based procedure or in an operating room (OR).
There are several injectables available, which appear to have similar efficacy but individually have unique biophysical properties. These include calcium hydroxyapatite, silicone particles, polyacrylamide hydrogel, and carbon beads. Collagen is no longer available for use.
Periurethral and transurethral injection techniques have been described, and both approaches appear to be reasonably safe and efficacious. A transurethral injection allows for direct visualization of the needle and thus more accurate localization of the bulking agent. It has been suggested that the periurethral injection technique may use a larger volume of injection material, and as such, patients may have a slightly higher rate of postoperative urinary retention. However, the periurethral approach may reduce local urethral trauma and bleeding as well as minimize extravasation of the bulking agent.
Precise placement of the bulking material at the proximal urethra is paramount to achieve adequate coaptation. Injection sites near the bladder neck are likely to be associated with extravasation into the bladder and poor coaptation; distal injections into the external sphincter can also result in treatment failure and may lead to pain and irritative voiding symptoms. The bulking agent should be injected slowly to allow the tissue to accommodate the material, prevent extrusion, and minimize patient discomfort. Care should be taken when removing the needle to avoid another mucosal puncture site.
Office-Based Transurethral Injection Technique
With an empty bladder, the patient is positioned in dorsal lithotomy and prepared according to standard sterile technique. Local anesthesia is then administered: A periurethral infiltration of injectable lidocaine or a transurethral insertion of topical lidocaine jelly may be used. A flexible cystourethroscope is advanced into the bladder and then slowly withdrawn until the lens is positioned to visualize the entire proximal urethra. The cystourethroscope is then turned 90 degrees, which places the tip of the injection needle at the 3 or 9 o’clock position of the urethra ( Fig. 101.1 ). The cystourethroscope is then tilted so that the lens and needle tip are pointed toward the urethral wall at a 30- to 45-degree angle. The needle is advanced until it just indents the urethral mucosa. Keeping the needle fixed so it cannot retract, the entire cystourethroscope is then moved sharply toward the urethral wall until the needle pops into the submucosal space ( Fig. 101.2 ). The cystourethroscope is returned to the neutral position to visualize the injection site and the urethral lumen. Under direct vision, 1 mL of 1% lidocaine is injected into the submucosal plane. Without moving the position of the needle, the bulking agent is then slowly injected into the same site. This may be repeated on the contralateral side to achieve adequate coaptation ( Fig. 101.3 ).