3.2.4. Location of Bladder Injection: Trigone or Bladder Body

Most studies have used BoNT-A bladder-body injection to treat patients with bladder disease [65]. For the inhibition of bladder contractility and associated adverse effects, some researchers have used BoNT-A injection in the trigone and bladder floor, rather than the entire bladder body, for patients with IC/BPS [54,61,62,66]. The trigone has been regarded as the sensory input center in the bladder since the 1970s [67]. Neurophysiology analysis revealed that the trigone contains significantly higher levels of adrenergic and muscarinic nerve innervation relative to the bladder body [67]. A recent three-dimensional image reconstruction analysis of the nerve further demonstrated that bladder autonomic innervation is concentrated in the bladder trigone [68]. The injection of BoNT-A in the bladder trigone to block nociceptive neurotransmitters is a reasonable procedure, and has the potential to avoid inhibition of bladder contractility. However, the mechanisms of IC/BPS pathogenesis include abnormal bladder sensory input, as well as active inflammation in the bladder body. The anti-inflammatory effect of BoNT-A trigone injection may be inferior to that of diffuse bladder-body injection. Our previous study compared BoNT-A injection in the bladder body with that of injection in the trigone in patients with idiopathic detrusor overactivity [69]. There were no significant differences in treatment success rates or changes in urgency severity score, and the incidence of adverse events was similar between trigone and bladder-body injections. Another animal study used BoNT-A injection on one side of the bladder and found that synaptosome-associated protein 25 was cleaved on the opposite side of the bladder [70]. The findings of that study demonstrate that BoNT-A injection could spread across the guinea pig bladder; this phenomenon also may occur in the human bladder. Theoretically, trigone and bladder body BoNT-A injections might have similar therapeutic effects, but comparison studies are needed to confirm this hypothesis. For elderly IC/BPS patients with inadequate bladder contractility, the use of BoNT-A trigone injection appears to be reasonable.
