Do “Conscious” and “Reflex” micturition have a separate sensory input? Implications for clinical urodynamics

Anatomical, neurophysiological, pharmacological, and clinical observations indicate the existence of multiple sensory pathways relaying information from the lower urinary tract to the central nervous system. The sensory input that activates “voluntary” (in humans) or “conscious” (in animals) micturition may be, at least in part, separate from that which activates “reflex” micturition. Recent observations obtained with capsaicin, a sensory neuron blocking agent, indicate that multiple sensory pathways may activate micturition and that these systems operate at a different threshold, eg, certain sensory systems are particularly sensitive to variations in filling rate. These advances in the physiopharmacology of the afferent branch of micturition suggest that the use of very different filling rates from one laboratory to another may be a major cause of heterogenicity of results in clinical urodynamics. Moreover, a complete and meaningful evaluation of the sensory function regulating micturition should include evaluation of the bladder response to both “low” (physiological) and “high” (provocative) filling rates.