Direct outcome measures such as urinary flow rates, detrusor pressures at maximum flow, and postvoid residuals are common historic measures used to evaluate the efficacy of therapy for LUTS. Improvement in urodynamic parameters after TURP compared with TUIP are typically slightly in favor of TURP, but the clinical significance when a difference is demonstrated is controversial. The improvement in urinary flow rate is typically greater after TURP, in the range of 0 to 4.1 mL/s greater than after TUIP. In two studies, detrusor pressure at maximum flow rate decreased more in the TURP group than in the TUIP
group, and the urethral pressure profile was shorter after the operation (6,30). Urodynamic improvements remained at a mean follow-up of 53 mo. At that time, the reported mean detrusor pressure at peak flow had decreased from 85 to 44 cm H2O, the maximum detrusor pressure had decreased from 114 to 55 cm H2O, and the mean maximum flow rate increased from 10.3 to 15.3 mL/s (23). The average urethral resistance factor value decreased from 41 cm H2O to the unobstructed range (16 cm H2O) (53). The size of the prostate was an important selection criterion in these studies (prostate volume < 30 cm) (23,30,54,55).
Of note, although urodynamic testing is helpful in many men pre-operatively, postoperative urodynamic data do not correlate with patient reported improvement. A reported 80% of all patients participating in urodynamic studies of transurethral resection, transurethral incision, and laser prostatectomy had obstruction before treatment, but the number of men who did not have obstruction after treatment was low (transurethral resection 51%; laser prostatectomy 41%, and transurethral incision 29%) (23,50-52,56).
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