Development of a novel mesh model to define a new index “amount of stone” to evaluate calculus and predicting the lithotripsy time

OBJECTIVE: Develop a mesh model to define a new “index amount of stone” to evaluate calculus and predict lithotripsy time. METHODS: The stones were divided into target units with diameter of 5 mm by the mesh from x, y and z directions, and the cross-sectional areas between units were calculated as amount of stone as a new index to evaluate calculus. Design a prospective study with 112 cases of percutaneous nephrolithotomy to verify the reliability of this index, and to compare the accuracy of the quantity, volume and maximum diameter of stones in predicting the time of lithotripsy. RESULTS: Amount of stone (Q) is reliable. The lithotripsy time was significantly correlated with the amount of stone, volume and maximum diameter of the stone (p < 0.01). The three regression equations were valid. The linear fit in the amount group was larger than that in the volume group, and further larger than that in the maximum diameter group, with R(2) values of 0.716, 0.661 and 0.471, respectively. CONCLUSIONS: It is more accurate and convenient to use amount of stone to evaluate calculus, which can be used to predict the lithotripsy time.