POSITION-RELATED CHANGES IN VOIDING DYNAMICS IN MEN

Objectives. To investigate by urodynamic study position-related change s in uroflowmetry and postvoid residual urine volume (PVR) in men beca use altered bladder function in the supine position may be a predispos ing factor for urinary tract infections in the institutionalized elder ly. Methods. Two healthy men, 34 and 59 years of age and living at hom e, and 55 nursing home residents (mean age 71.8 years, range 46 to 92) were evaluated with uroflowmetry in the standing and recumbent positi ons (lying on the left or right side); corresponding PVRs were measure d by transabdominal ultrasonic bladder scanning. The two healthy men w ere monitored longitudinally with multiple recordings in both voiding positions, and the nursing home residents were subjected to two observ ations: one measurement of the variable parameters in either position. Differences were considered to be significant at P < 0.05. Results. T he 34-year-old man performed 513 flows (368 standing and 145 recumbent ). The mean of all the peak flow rates in the upright (28.2 +/- 4.2 mL /s) versus the recumbent (16.8 +/- 4.1 mL/s) position revealed a highl y significant difference (P = 0.0001). Sixteen urinary flows and corre sponding PVRs were completed by this subject in either voiding positio n. The difference between PVRs in the standing (13.1 +/- 14.7 mL) vers us recumbent (15.3 +/- 17.5 mL) position was not statistically signifi cant. The 59-year-old man completed 156 flows (128 standing and 28 rec umbent). A highly significant difference was noted between the mean of all peak flows in the upright (18.9 +/- 4.1 mL/s) versus recumbent (1 2.6 +/- 2.0 mL/s) position (P = 0.0001). Thirty-seven urinary flows an d corresponding PVRs were completed by this individual (10 PVRs were d etermined after voiding in the standing and 27 after voiding in the re cumbent position). No significant difference was noted between PVRs in the standing (24.6 +/- 34.4 mL) versus recumbent (16.5 +/- 60.0 mL) p osition. In the nursing home residents, the difference between the mea n peak flow rates in the standing (14.5 +/- 8.6 mL/s) versus recumbent (12.4 +/- 6.7 mL/s) position also reached statistical significance (P = 0.0084). The difference between PVRs in the standing (60.5 +/- 125. 6 mL) versus recumbent (84.8 +/- 186.2 mL) position barely reached sta tistical significance (P = 0.0497). Conclusions. The urinary flow rate decreases in the recumbent position. Bedridden residents may be predi sposed to urinary tract infections because of alterations in voiding d ynamics in the supine position. This area needs further study. UROLOGY 52: 625-630, 1998. (C) 1998, Elsevier Science Inc. All rights reserve d.