Diagnosis of Urethral Resistance in Men: 70 Years of History

BACKGROUND AND AIMS: The urethral resistance (UR) is one of the key outcomes of the urodynamic pressure-flow study (PFS) in men. Combined with a clinical meaningful cut-off point, urodynamic bladder outflow obstruction (BOO) can be determined. This characterization of BOO provides guidance in the management of lower urinary tract symptoms (LUTS), enabling the differentiation between BOO and detrusor underactivity. In this way, the UR can be objectified and monitored, providing insight into the expected results of a clinical intervention. The route from the raw urodynamic measurement towards the diagnosis has faced fundamental challenges over the years. This narrative review aims to give an overview of the background of our current UR measures in men and provides an outlook towards new developments. METHODS: A non-structured literature search was conducted into the development of assessment of UR. RESULTS: A narrative historic overview is given of the development of assessment of UR. CONCLUSION: The history of assessing urethral resistance centers on simplifying complex fluid dynamics into clinical tools, evolving from static calculations to dynamic, tissue-elasticity. Today, a renewed focus on voiding physiology, paired with machine learning and computational fluid dynamics, promises mathematically valid, patient-specific diagnostics to optimize the management of bladder outflow obstruction.