Aim: To explore the interaction between bladder compliance (BC) and bladder outflow obstruction (BOO) in men with benign prostatic hyperplasia (BPH) using cross-sectional and longitudinal studies.

Methods: A total of 181 men with BPH were recruited, and 100 of them were followed for one year. Cystometry was performed in a standing or a sitting position with 30 mL/min infusion. BC was manually corrected and defined. Obstruction coefficient (OCO), linear passive urethral resistance relation and international continence society (ICS) nomogram were used to diagnose BOO. The obstructed parameters were compared between the reduced BC group and the non-reduced group. BC was compared between the first investigation at the beginning of study and the second investigation at the end of study during the one-year follow-up period.

Results: The group with reduced BC had increased OCO and linear passive urethral resistance relation. BC was significantly lower in the obstructed group (55.7 mL/cm water) than that in unobstructed and equivocal one (74.9 mL/cm water, P < 0.01). BC gradually reduced with the increased obstructed grade. There was a significantly weak negative correlation between BC and OCO (r = - 0.132, P < 0.01). Over the one-year follow-up period in the longitudinal study, BC for all men changed from 54.4 to 48.8 mL/cm water (P > 0.05), and BC for the group with BOO fell from 58.4 70.1 to 46.5 38.7 mL/cm water (P > 0.05).

Conclusion: In men with BPH, a significant systematic decrease occurred in BC in the obstructed group and a significant systematic increase with urethral resistance occurred in the low BC group. A longitudinal study of the tendency of BC reduction in a group with BOO is necessary in the future.

Keywords: benign prostatic hyperplasia, bladder compliance, bladder outflow obstruction

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