Bladder Trigone as a Sensory Hub: A Narrative Review.

The bladder trigone is an anatomically and functionally distinct region within the lower urinary tract (LUT), characterized by a dense network of afferent sensory fibers, specialized urothelial interactions, and prominent mechanotransduction mechanisms. Its intricate neuroarchitecture enables precise detection of bladder filling and coordination of micturition, whereas dysregulation of these pathways contributes to lower urinary tract symptoms (LUTS), including urgency, frequency, and bladder pain. Despite its recognized clinical relevance, the structural and functional basis of trigonal sensory signaling - and its role - remain incompletely understood. This review synthesizes current evidence on trigonal afferent organization, integrating data from anatomical mapping, receptor profiling, electrophysiological characterization, and translational research. Seminal anatomical observations are combined with recent advances in mechanotransduction and purinergic, peptidergic, and transient receptor potential (TRP) signaling to provide a comprehensive perspective. The trigone exhibits three principal afferent classes: (1) intraepithelial fibers penetrating umbrella cells, marked by P2X purinoceptor 3 (P2X3), transient receptor potential vanilloid 1 (TRPV1), calcitonin gene-related peptide (CGRP), and substance P (SP); (2) subepithelial plexuses surrounding microvasculature, enriched in vasoactive neuropeptides and exhibiting plastic hypertrophy in overactive bladder (OAB) and interstitial cystitis/bladder pain syndrome (IC/BPS); and (3) encapsulated corpuscular endings at the lamina propria-detrusor junction, expressing PIEZO1/2 and acid-sensing ion channels (ASICs) for rapid adaptation. In trigeminal dorsal root ganglion (DRG) neurons, high expression of PIEZO2, P2RX3, and voltage-gated sodium channel, type 1.8 (Nav1.8) was observed, revealing their role as the foundation for multisensory information processing. Functional assays highlight distinct mechanotransductive and chemosensory pathways, with aging, inflammation, and neurotrophic factors driving afferent plasticity underlying abnormal bladder sensation, such as urgency, frequency, and pain. Early clinical trials of P2X3 antagonists and intravesical TRPV1 inhibitors demonstrate promising symptomatic benefits. Collectively, evidence positions the bladder trigone as a critical sensory hub where neuronal, urothelial, and immune signals converge to regulate bladder sensation. Understanding its molecular and structural specialization may inform the development of region-specific neuromodulatory therapies targeting sensory urgency and afferent-driven bladder dysfunction.