THE STONE CLINIC EFFECT - MYTH OR REALITY

Sixty-six active recurrent stone formers (RSF), i.e., with at least on e stone annually over 3 years prior to the first examination at our st one clinic, were retrospectively evaluated. All received specific drug metaphylaxis which was discontinued after 5.5 +/- 2.1 years (period 1 ). They were reclassified according to the above definition into activ e and inactive RSF and were then left on a general metaphylactic regim en with regular urological follow-up every 6 months (period 2). 32 pat ients observed these recommendations for 5.7 +/- 2.6 years(group 1), 3 4 did not. 20 of these 34 could be reexamined after 6.3 +/- 2.2 years (group 2). Group 1 comprised 10 active and 22 inactive, group 2 compri sed 1 active and 19 inactive RSF. While the recurrence rates among the inactive RSF of groups 1 and 2 decreased significantly during period 2, a statistically significant difference between them was not observe d. Conversely, there was only a slight reduction of the recurrence rat e in the active RSF. Both findings argue against a stone clinic effect . Interviews of the patients showed that stone formation was periodica l for a mean of 12 +/- 8 years, after which it gradually faded out. Th is period is termed 'phase of regular stone formation' and appears to be an autonomous process that cannot usually be influenced by metaphyl actic measures. This could explain the wide variability of reported su ccess rates for the various metaphylactic regimens, as they would mere ly reflect the number of stone formers who are in their phase of regul ar stone formation.