Can the bladder itself “measure” volume, and thereby help to determine when initiation of voiding should occur? Ici-rs 2024

Aims
To answer the question of whether the bladder itself can to any extent control or modulate the initiation of voiding.

Methods
This subject was discussed at the International Consultation on Incontinence-Research Society (ICI-RS) 2024 conference in Bristol, UK in a proposal session.

Results
Cells in the bladder wall sense the local environment via a diverse array of ion channels and receptors which together provide input to motor-sensory and signal transduction mechanisms. A purinergic signal transduction system provides a high-gain mucosal chemosensitive transduction pathway between bladder wall stretch during filling and graded afferent activation. Recent studies established cross-species similarities in the regulation of urine storage which include the upregulation of aquaporin (water) channels during bladder filling/wall stretch, in the bladder. In addition to the endocrine hypothalamus/pituitary axis production, urothelial production of arginine vasopressin acts on urothelial vasopressin receptors in a paracrine manner causing aquaporin channel upregulation, reducing the bladder volume and delaying sensation of fullness. Bladder shape influences the sensory systems involved in the perception of bladder volume; moreover irregular bladder shapes may correlate with overactive bladder.

Conclusions
Volume measuring and signaling threshold-determining mechanisms in the bladder along with shape and permeability act to influence the timing and type of signaling to the CNS; although this is not always followed by a consecutive action. The hierarchical grading of the signals originating from the bladder among other peripheral bodily or central signals are crucial factors that determine whether the bladder is “allowed” to initiate voiding.