Diagnostic clues for low-pressure female bladder outflow obstruction overlooked by conventional urodynamics

Female bladder outflow obstruction is typically characterized by high-pressure, low-flow patterns. However, low-pressure, low-flow variants are frequently overlooked by conventional urodynamic studies. This study aims to identify clinical predictors of low-pressure bladder outflow obstruction in women categorized as non-obstructed by standard criteria.

We retrospectively reviewed women with lower urinary tract symptoms who underwent videourodynamics between 2012 and 2020. Conventional obstruction was defined as maximal flow rate of less than 12 milliliters per second combined with a detrusor pressure at maximal flow of greater than 20 centimeters of water. Patients not meeting these parameters were evaluated for low-pressure obstruction, confirmed via fluoroscopic evidence during videourodynamics.

Among 419 women classified as non-obstructed by conventional urodynamics, 128 (30.5%) demonstrated low-pressure bladder outflow obstruction on videourodynamics. Multivariable logistic regression identified a history of anti-incontinence or pelvic organ prolapse surgery and an International Prostate Symptom Score voiding-to-storage subscore ratio greater than 1 as significant independent predictors. Conversely, age 70 years or older and a mean flow rate of 10 milliliters per second or greater served as independent negative predictors.

Approximately 30% of women deemed non-obstructed by conventional urodynamics exhibit low-pressure bladder outflow obstruction. Clinicians should prioritize further evaluation with videourodynamics in patients with prior anti-incontinence surgery, a high International Prostate Symptom Score voiding-to-storage subscore ratio, younger age, or low mean flow rates to prevent misdiagnosis.