Urology has traditionally been an endoscopic specialty, being at the forefront of minimally invasive and diagnostic interventions based on this technology. With scientific advances and miniaturization of equipment, access devices initially designed for adults have been easier to transfer to the pediatric population. Indeed, it is this process that has allowed for easier (nontraumatic) entry through the meatus and urethra, avoiding subsequent problems, most notably iatrogenic trauma and stricture formation. The ultimate testament to this miniaturization process has been the commonplace use of transurethral resection of posterior urethral valves or incision of obstructing ureteroceles in neonates, considered by many the standard of care for the initial management of these conditions with the use of infant resectoscopes.

In many ways, endoscopic techniques represent one of the most common forms of “natural opening” surgery, gaining access to the lower urinary tract via the urethral meatus. Far from being solely employed as a diagnostic intervention (as often seen in older patients), access allows delivery of different substances directly into the bladder neck, trigone, or detrusor muscle, aided by a needle with standardized depth mark(s). As such, endourological access is a means of delivery, rather than a surgical technique per se; the challenge centers on performing the actual administration and the rationale for selecting such intervention over other options. These procedures are commonly shorter in duration and associated with quicker recovery, with the obvious advantage of not generating visible scars. Nevertheless, although appealing in its simplicity and lack of invasiveness, contrast with traditional (open) techniques often demonstrates lower efficacy and – due to their novelty – shorter follow-up.

With little doubt, pediatric urology grew as a subspecialty with the acceptance of vesicoureteral reflux as an important clinical entity, amenable to surgical correction in order to limit short- and long-term morbidity [1]. This popularization generated a “need” for surgical treatment, questioned by many due to the morbidity of the procedure, particularly for low grades of reflux in otherwise healthy children, thus fueling the role of nonsurgical and less-invasive surgical options. The widespread use of endoscopic injection has its origins on the landmark work by Puri and O’Donnell who pioneered the use of Teflon^® as a bulking agent to manage this condition in a minimally invasive fashion [2]. The technique (so-called classic STING) involved a single submucosal injection at the 6 o’clock position of the ureteral meatus. Although initially met with skepticism and some resistance, a few decades later this delivery modality (with some modifications) has surpassed in popularity other surgical options in many parts of the world. Even though the employed bulking substance has changed, currently heavily favoring dextranomer/hyaluronic acid, the administration principles remain fundamentally unchanged. In addition, the attractiveness of lower surgical morbidity by taking advantage of natural entry points fueled enthusiasm for expanding the application to other conditions. It is probably fair to say that the contemporary success and enthusiasm for endoscopic injection largely rest on this pioneer work.

The “art” of endoscopic treatment heavily weighs on the injection technique rather than access. Cystoscopy is a basic urological skill, and getting to the injection site adds little in terms of additional challenge, except for minor adjustments that are required when employing a straight working channel (angled or offset ocular) scope, as well as negotiating the urethra, of limited caliber and potentially more delicate than in adults. On occasion, entry options may be limited or favored to a catheterizable channel (i.e., Mitrofanoff or Monti-Yang), which needs to be negotiated as gently as possible, and drug delivery adjusted based on the limitations imposed by the different “view” obtained.

The injection technique itself has to be adapted to the indication for surgery and the substance to be delivered. For vesicoureteral reflux, most commonly treated by injection of dextranomer/hyaluronic acid, the compound is precisely placed in a submucosal plane – through one or two injection sites – at the level of the ureteral orifice and intramural ureter. Similarly, in selected cases, this substance can be delivered at the bladder neck/proximal urethra level to create resistance (or “controlled obstruction”), in an attempt to address stress urinary incontinence. In contrast, botulinum toxin is injected at multiple sites in order to cover the muscle mass targeted for temporary paralysis. The latter case is seemingly less impacted by a steep learning curve, yet requires skill avoiding limited visualization as the case progresses due to early injury of large submucosal vessels, as well as good spatial planning in order to evenly distribute the fixed predetermined dose of diluted botulinum toxin throughout the treatment area.

In the following paragraphs, we will address specific issues based on injection sites and pathology, attempting to create a clear distinction between the detrusor muscle, ureterovesical junction, and bladder neck/sphincter. In addition, the authors’ preference for endoscopic management is summarized in Tables 24.1, 24.2, and 24.3.