Objective   To investigate the accuracy and feasibility of the pressure-flow studies (PFS) carried out in 45° semi-reclining position in patients with benign prostatic hyperplasia (BPH).    Methods   The cases of BPH admitted to our de

partment to receive prostatectomy between November

2007 and May

2008 were divided into 2 groups randomly. Before the operation

each patient continuously underwent PFS twice in 45° semi-reclining and standing position

respectively. A total of 60 cases were included

either group A or group B consisted of 30 cases. The PFS was carried out in 45° semi-reclining position first

and then in standing position in group A

but conversely in group B. The data were analyzed by UNIANOVA with SPSS 13.0.    Results   Of the 60 cases

48 (80%) had good flow curves in both 45° semi-reclining and standing position. No significant difference was noted in the Qmax between 45° semi-reclining [6.079±3.485 ml/s

with 95% CI of the mean (5.712

6.436)

]

and standing position [6.390±3.903 ml/s

with 95% CI of the mean (6.033

6.757)

]

. But a highly significant difference was noted in the Pdet.Qmax between in 45° semi-reclining [72.844±37.800 cmH

2

O

with 95%CI of the mean(70.736

74.808)

]

versus standing position [82.917±38.681 cmH

2

O

with 95% CI of the mean(80.953

85.024)

]

(P=0.000). The AG number in 45° semi-reclining [60.788±40.000

with 95%CI of the mean (58.471

62.956)

]

and standing position [70.256±41.893

with 95%CI of the mean (68.081

72.567)

]

revealed a highly significant difference (P=0.000). The URA in 45° semi-reclining [46.576±23.595

with 95%CI of the mean (44.535

48.598)

]

and standing position [51.512±25.503

with 95%CI of the mean (49.490

53.552)

]

also showed statistical significance (P=0.001). The other 12 cases (20%) had flow curves only in standing position but did not (unable to void) in 45° semi-reclining position.    Conclusion   The accuracy and feasibility of the PFS carried out in 45° semi-reclining position are not as good as in standing position for patients with BPH.