SUFU 2021: Impact of Technique on Outcomes With Botulinum Toxin Injection

( Dr. Michael Kennelly’s lecture centered on the specifics of Botulinum toxin (BTX) injections. The standard injections are: 

 • OAB: 20 intra-detrusor injections of 0.5 mL
(100 U in 10 mL = 5 U per 0.5 mL injection + 1 mL flush (saline)
• NDO: 30 intra-detrusor injections of 1,05 mL
(200 U in 30 mL = 6.7 U per 1.0 mL injection + 1 mL flush (saline)

Instructions included priming the needle with approximately 1 mL of BTX prior to starting the injections so as to remove any air. To inject approximately 1 cm apart and approximately 2 mm deep and with the final injection, inject approximately 1 mL of non-preserved saline so that the remaining BTX in the needle is delivered to the bladder.  A successful outcome is determined by physician technique, product performance, and patient factors. His lecture focused on the physician technique. He noted the variables affecting injection technique including BTX dose, injection location (local vs diffuse, detrusor vs submucosal, trigone vs non-trigone), number of injections, concentration and volume of injection, equipment used (rigid vs flexible scope), and ancillary procedures (hydrodistension).

BTX studies have shown a dose-dependent efficacy but higher doses can lead to retention. The therapeutic effect does not depend on the number of injections but rather on the BTX dose and solutions. The injection location can be either submucosal, where the sensory receptors on urothelial cells are found and where adenosine triphosphate (ATP) is released, or in the detrusor muscle (2-4 mm deep) which is rich in acetylcholine motor nerves. BTX-A blocks ATP release and decreases acetylcholine (ACh) release. Depending on the bladder wall thickness, deep injections could diffuse out of the bladder and superficial injections could diffuse out of the needle site limiting effectiveness. Originally, injecting in the trigone was not recommended because of a concern of vesicoureteral reflux but that has been disproved.

As to the injection volume, Dr. Kennelly feels there are advantages and disadvantages. Injecting a volume of 0.5 mL is a quicker procedure, fewer syringes are used, less patient pain but there is a higher chance of fluid loss if the needle is not placed in the urothelium. Injecting 1.0 mL has a better chance of correct placement as you can inject deeper, there are more surface area coverage and better vision of injection location.  In conclusion, Dr. Kennelly feels following specific techniques for BTX injections can lead to improved outcomes. 

Presented by: Michael J. Kennelly, MD FACS Professor, Department of Urology & Gynecology, Director, Charlotte Continence Center Carolinas Medical Center, Atrium Health, Charlotte, NC

Written by: Diane K. Newman, DNP, CRNP, FAAN, BCB-PMD, Nurse Practioner and Co-Director, Penn Center for Continence and Pelvic Health Adjunct Professor of Urology in Surgery during the 2021 Society of Urodynamics, Female Pelvic Medicine & Urogenital Reconstruction (SUFU) Winter Meeting.