RESUMO
Objective To investigate the three-dimensional structure of normal male canine prostat- ic duct and acinus system,and to study the mechanism of intraprostatic urinary reflux(IPUR)resulting from high pressure of the posterior urethra by experiment.Methods Using scanning electron microscopy (SEM)and corrosion casting methods,high pressure of the prostatic urethra was produced based upon IPUR in normal male canines.Acrylonitrile-butadiene-styrene(ABS)casting solution was injected into 8 Beagle canines'normal prostates to induce intraprostatie resin solution reflux.Results Six casting molds of nor- real canine prostate specimens were obtained,and the casting failed in 2.By corrosion and casting treatment, the prostate appeared to consist of several glandular lobes.The columnar apophyses of glandular surface were observed.The most glandular ducts pointed outward from urethral peristome.Each glandular duct system was made up of many bifurcated branches from the bough as a duct tree.More than 90% of the bifurcations were Y-shaped,and 6 bifurcated branches were rarely seen.The tip of the duct was vesicular.The diameter and length of the bough were(0.37?0.14)mm and(1.14?0.04)mm,respectively.The intersectional angle of urethra and peripheral glandular duct was the biggest.Peripheral glandular duct was perpendicular or con- verse to urinary flow.Peripheral glandular aeinus appeared elliptic and velvet.The mesh-like and crater-like depressions were shown on the surface of central glandular aeinus.Ejaculatory ducts independently and branchlessly entered the urethra.Conclusions The resin corrosion casting methods combined with SEM can clearly show the three-dimensional structure of normal male canine prostatic duct and acinus system. IPUR may easily occur in the peripheral glands from the morphological view.It is suggested that prostatitis occurs more commonly in peripheral glands,confirming a fact that high pressure of the posterior urethra can induce IPUR.