α‐blockers improve chronic ischaemia of the lower urinary tract in patients with lower urinary tract symptoms

Abstract

To investigate whether a mechanism of action of alpha-blockers on lower urinary tract symptoms (LUTS) involves improved perfusion of the LUT. The accuracy of perfusion measurements using transrectal colour Doppler ultrasound (TRCDUS) and colour pixel density (CPD) was initially confirmed in a porcine model. Following this confirmation, measurements were taken from four healthy male volunteers and 19 patients with LUTS. The urinary bladder was filled slowly (50 mL/min) with 0.2 m KCl, which resembles the osmolarity of concentrated urine, and evaluated by cystometry. In parallel, TRCDUS and measurement of the CPD of the LUT were performed. The patients with LUTS were then treated with daily alpha-blocker (0.4 mg tamsulosin) for 5 weeks and urodynamic variables as well as perfusion were evaluated again. In the healthy men, perfusion of the LUT increased considerably (157%) during filling of the bladder to a mean (sd) maximum cystometric capacity (C(max)) of 481 (28.9) mL. All the patients with LUTS had a reduced mean C(max) during filling with KCl at 322.4 (58.5) mL. The mean CPD in the urinary bladder and the prostate were only increased by 58.4% during filling with KCl. After alpha-blocker therapy the mean C(max) during filling with KCl rose to 382.5 (42.9) mL; furthermore, perfusion of the LUT measured by CPD was significantly increased (132.8%). The present data strongly suggest that LUTS are associated with chronic ischaemia of the prostate and urinary bladder. alpha-blockers increase perfusion in the LUT and C(max). These results might explain the therapeutic effects of alpha-blockers on LUTS.