Acute urinary retention: defining the need and timing for pressure-flow studies

Objective To investigate the utility of 'late' pressure-flow studies in predicting the outcome of prostatectomy for acute urinary retention. Patients and methods Fifty-eight patients with acute urinary retention were prospectively assessed using the International Prostate Symptom Score and pressure-flow studies at a median (range) of 24 (13-60) days after the episode of retention, and before transurethral resection of the prostate. Bladder outlet obstruction and bladder contractility were graded using a modified adaptation of Schafer's passive urethral linear resistance relation. Results Fifty-six (97%) patients generated a voluntary detrusor contraction, with a mean (range) detrusor pressure at maximum flow of 72.7 (5-144) cmH(2)O, and 43 (75%) patients were deemed to be obstructed. Eight (16%) patients failed to void after prostatectomy and required clean intermittent catheterization. There were statistically significant differences between successful and Unsuccessful patients in mean (SD) age, at 66.30 (6.9) vs 78.8 (2.6) years (P=0.001), detrusor instability (49%, vs 0%, P=0.01), inability to void during pressure Study (8% vs 75%. P=0.001), and maximal detrusor pressure in the voiding phase, at 80 (36.0) vs 19 (11.2) cmH(2)O (P=0.001). Conclusions In patients with acute urinary retention, pressure-flow studies undertaken after a period of adequate bladder rest ( > 3 weeks) are useful in predicting the surgical outcome. Old age, absence of bladder instability. inability to void during the pressure-flow study and a maximal detrusor pressure of < 20 cmH(2)O are associated with a poor outcome after prostatectomy.