Can renal stone size and the use of the nephrolithometric system increase the efficacy of predicting the risk of failure of percutaneous nephrolithotripsy?

OBJECTIVE: to verify the association of success rate of percutaneous lithotripsy, Guy score and size of the stone.
METHODS: one hundred patients submitted to percutaneous nephrolithotripsy were evaluated. All stones were classified according to Guy Score. Patient free of stone was considered when residual fragments were ≤2mm.
RESULTS: according to guy Score, 54% were score 1 (Group 1), 18% score 2 (Group 2), 15% score 3 (Group 3), and 13% score 4 (Group 4). Success was observed in 77.77% in Group 1, 27.77% in group 2, 26.6% in Group 3, and 7.69% in Group 4. In patients with Guy score 1, there was statistical significance of prediction of free stone rate when evaluated according to the size of the stone. Among groups 2, 3 and 4 there was no statistical significance, but it was observed a trend in relation to stone size, the bigger the higher the chance of residual fragments.
CONCLUSION: nephrolithometry by Guy Score and size of the stone are single predictors of success of percutaneous nephrolithotripsy. Stone size may influence success rate of patients with Guy Score 1.