[Structure of secondary or exogenous prostatic calculi].

Out of a series of 70 prostatic stones, we found 8 considered to be "secondary" or "exogenous" (i.e. originated inside the acinis, following the initial crystallization of the components of the orine introduced into the acini) which underwent crystallographic analysis, using basically the "fine plate" to determine their structure. There were found to be two types of stones: one kin essentially uric (5 in all) and others essentially oxalic (3). We observed that these may be formed by pure substances as in the case of two uric stones but generally the nucleus is made up of uric or oxalic components with a tendency in the periphery to form concentric layers of apatite or whitlockite, similar to those observed in primary or endogenous prostatic stones, accompanied by other oxalic or uric components or not. We found that both the uric acid (anhydrous) as well as the oxalates may adopt the same strucutre presented by the urinary stones (renal, vesical) but the anhydrous, uric acid may also present in the nucleus of a stone, an association of 3 structures (granuloporous + fibrosoradiated + palisaded) which does not occur in urinary stones and it may also form a structure which we call "concretioning" which has not previously been described.