RESUMO
<p><b>OBJECTIVE</b>To investigate the composition and morphology of the stones in the enlarged prostatic utricle (EPU).</p><p><b>METHODS</b>We took out 36 EPU stones from 11 patients by transurethral fenestration between 1992 and 2011, and analyzed the stones by scanning electron microscopy, x-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIS).</p><p><b>RESULTS</b>Under the scanning electron microscope, all the EPU stones were constituted of many intensive minicrystals and amorphous matrix. XRD and FTIS revealed that all were hydroxyapatite crystal.</p><p><b>CONCLUSION</b>EPU stones belong to the category of prostatic pseudo-calculi, whose formation is ascribed not to the abnormal change of urine composition, but to the continuous secretion, absorption and concentration of EPU liquid and ablated epithelial cells from the EPU.</p>