Introduction
Bladder outlet obstruction is often under diagnosed in women. It is associated with voiding lower urinary tract symptoms consisting of weak stream and incomplete bladder emptying as well as storage symptoms consisting of frequency, nocturia, and urinary incontinence. The categories of bladder outlet obstruction are divided into anatomical and functional causes. Anatomical causes include pelvic organ prolapse and post-urinary incontinence surgeries while functional causes include primary neck obstruction and small fiber neuropathy leading to autonomic dysfunction. In order to accurately diagnose bladder outlet obstruction, a comprehensive history, physical exam, and diagnostic testing need to be undertaken. On urodynamic studies (UDS), increased detrusor pressure, no Valsalva or change in abdominal pressure, minimum urinary flow, and EMG synergy in the presence of sustained bladder contraction represent bladder outlet obstruction. The obstruction may also be seen on cystography at the level of the bladder neck. We sought to evaluate the effectiveness of onabotulinumtoxin A at the level of the bladder neck in patients with bladder neck obstruction, many of whom have small fiber neuropathy.
Design
During the chemodenervation procedure, a female urethral cystoscope, 100 units of onabotulinum toxin A, and a 23 gauge cystoscopic injection needle are needed. The 100 unit onabotulinum toxin is reconstituted with 2cc of preservative free injectable saline, making it more concentrated than standard mixing based on the small target for delivery. Using a 30-degree lens and rigid cystoscopic sheath a cystoscopy is performed for general surveillance prior to the onabotulinum toxin A administration.
After the cystoscopic injection needle is primed and loaded into the cystoscope injection port, 0.5cc of reconstituted onabotulinum toxin is injected four times evenly across the meat of the bladder neck at the 1, 5, 7, and 11 o’clock positions. During the procedure, the needle is cautiously directed distally enough to prevent through and through passage of the needle and wasting of the onabotulinum toxin into the bladder. The syringe is then changed to injectable saline with the tip of the needle still inserted in the bladder neck to prevent loss of the onabotulinum toxin held within the needle. The last injection is followed with an injection of 0.5cc of saline to clear the needle. Lastly, the bladder is drained, and the cystoscope is removed.
Results
In patients with bladder neck obstruction either due to primary cause or due to small fiber neuropathy, we have found that onabotulinum toxin A can be used at the level of the bladder neck to relieve obstructive symptoms for about 6 months. This treatment is best applied to patients who have UDS evidence of bladder neck obstruction, small fiber neuropathy, symptoms of hesitancy and dysuria, and have had inadequate response or poor tolerance to alpha blockers. Bladder outlet obstruction symptoms may worsen for one to three weeks as the chemodenervation treatment takes hold. Formal analysis of data has not been performed for this video technique demonstration. This is currently an off label chemodenervation treatment.
Conclusion
Onabotulinum toxin to the bladder neck is a treatment option in those with non-anatomic bladder neck obstruction who have not responded to conservative therapy. Pelvic floor physical therapy and relaxation techniques are usually offered as adjunct therapy for often present concurrent voiding dysfunction. Patients should be counseled on potential symptom flare-ups as the chemodenervation treatment is taking hold and that it may take one to three weeks for the treatment to set in.
References
Akikwala TV, Fleischman N, Nitti VW. Comparison of diagnostic criteria for female bladder outlet obstruction. J Urol. 2006;176(5):2093-2097. doi:10.1016/j.juro.2006.07.031
