Objective    Lactic acid is supposed to trigger the process of chronic nonbacterial prostatitis. To prove this hypothesis

lactic acid was introduced as an irritating agent to induce mice’s histological nonbacterial prostatitis by pelvic floor injection.     Methods    Adolescent mice received repeated injections of lactic acid (0.03 mol/L

0.1 ml per time) on the 1

st

2

nd

4

th

7

th

days. Each of them was sacrificed on the second day after their last injection. All dissected prostates were fixed in formalin and then sectioned for HE staining.     Results    The prostates under

going serials of inflammatory changes sequenced as: edema and venous dilation in the stroma

lymphocytes infiltration of the stroma and periglandular region

inflammatory exudates within the acinus. Besides

distinctive epithelial proliferation change was observed on the 8

th

day which is basically similar to PIN-like lesion in human prostate.     Conclusion    Lactic acid induced histological prostatitis replicates the pathological changes observed in clinical patients

suggesting the aggregation of lactic acid in the pelvic region plays an important role in the pathogenesis of chronic nonbacterial prostatitis. This study also supports the association between chronic prostatitis and later prostate cancer in a mouse model.