Dynamic URP: Revisiting Urethral Retro-Resistance Pressure for Contemporary Sphincter-Targeted Therapy

This paper introduces a new conceptual framework for interpreting urethral retro-resistance pressure (URP) as a dynamic, intra-procedural tool-ΔURP-for evaluating external urethral sphincter (EUS) engagement during injection therapy. With renewed interest in therapies that directly target the EUS, there is a critical need for real-time functional feedback at the site of action. This conceptual review re-examines URP in the context of emerging EUS-targeted treatments-such as bulking agents, regenerative injections, and neuromodulatory interventions-and proposes a dynamic model (ΔURP) to measure changes in sphincteric resistance as a functional biomarker during intervention. We review the anatomical, neurophysiological, and histological features of the EUS complex; trace the clinical rise and decline of URP; and compare its utility to conventional diagnostic tools. ΔURP, defined as the change in URP from baseline, is explored as an objective measure of EUS function. We outline its potential applications in guiding therapy, evaluating response, and standardizing outcomes across treatments. Conventional urodynamic measures fail to isolate distal sphincter function. In contrast, URP directly challenges the EUS and, when combined with imaging or procedural tools, may provide real-time feedback on sphincter engagement. When reframed as a dynamic, motion-based readout, URP may fill a critical gap in procedural urology-offering a physiologic signal of therapeutic engagement during EUS-targeted interventions. ΔURP has the potential to revive and repurpose a once-abandoned method into a clinically actionable biomarker for next-generation continence care.