What Are the Limitations of Measuring Bladder Compliance, As the Sole Indicator of Future Risk to the Upper Urinary Tract and Renal Function? ICI‐RS 2025

INTRODUCTION: Maintenance of bladder filling and urinary storage at low intravesical pressures is fundamental to minimizing risk to the upper urinary tract. Bladder compliance describes the relationship between the bladder volume and the change in detrusor pressure during the filling phase of urodynamics. Although significant clinical studies were performed 40 years ago, as currently conceived, the concept of bladder compliance and the associated normative values are inexact as an isolated measurement in predicting upper urinary tract deterioration in individual patients. The purpose of this review is to better define some of these limitations and propose potential means of addressing them. METHODS: The ICI-RS meeting was held in Bristol, England in June 2025, and Proposal 4 reviewed the current limitations of measuring bladder compliance as a predictor of upper urinary tract deterioration. Several ideas were discussed regarding the existing shortcomings of this parameter as well as potential methods of improving its measurement and prognostic value. Future research questions were reviewed and prioritized. RESULTS: The current methods of measurement and normative values for bladder compliance are inadequate for assessing upper urinary tract risk in many patients. The urodynamic technique for assessing compliance is not standardized among investigators resulting in potential variances between patients and centres. In addition, many patients undergoing urodynamics have very abnormal lower urinary tract anatomy. Such differences in structure, if not accounted for, could impact compliance assessment. Finally, the current "gold standard" of assessing compliance, the pressure-flow urodynamic study, involves catheters and is expensive, and itself may not account for a number of other factors which could potentially affect upper urinary tract risk. Alternative methods of assessing bladder compliance and upper urinary tract risk are investigational but may have some improved prognostic value. CONCLUSIONS: Prediciting upper urinary tract deterioration due to abnormalities of bladder compliance remains inexact as an isolated metric. The reasons for the lack of sensitivity and specificity are not well understood. Identifying the limitations of bladder compliance, modifying its assessment or combining it with other clinical or biological measurements may provide better and more precise prognostic information. In the meantime, advice is given on a "common sense" way by which UDS can be modified in relevant patient, in order to provide information that improves management and surveillance of vulnerable patients at risk from renal damage.