Kim et al reported several nomograms for predicting stone-free status after shock wave lithotripsy. One model is based on data after the first session with CT data available. The authors are from Seoul National University and affiliated hospitals in Seoul, Korea.
Patient selection: nephrolithiasis after first session of shock wave lithotripsy (SWL)
Parameters:
(1) sex
(2) stone location
(3) stone number
(4) maximal stone diameter in mm, from 2 to 26 mm
(5) grade of hydronephrosis
(6) Hounsfield units (HU) of the stone, from 0 to 2,000
points for stone diameter =
= 42.24 - (1.625 * (diameter))
points for Hounsfield units =
= 100 - (0.05 * (HU))
|
Parameter
|
Finding
|
Points
|
|
sex
|
male
|
0
|
|
|
female
|
2.3
|
|
stone location
|
lower calyx
|
0
|
|
|
renal pelvis
|
2.3
|
|
|
upper or middle calcyx
|
7.5
|
|
|
upper or middle ureter
|
25.5
|
|
|
lower ureter
|
10.6
|
|
|
UPJ (ureteropelvic junction)
|
23.1
|
|
stone number
|
1
|
13.8
|
|
|
2 or 3
|
5.4
|
|
|
>= 4
|
0
|
|
hydronephrosis
|
none
|
15.4
|
|
|
Grade 1
|
16.9
|
|
|
Grade 2
|
12.3
|
|
|
Grade 3
|
11.5
|
|
|
Grade 4
|
0
|
total score =
= SUM(points for all of the parameters)
Interpretation:
• minimum score: 0
• maximum score: 197.7
value of X =
= (0.04828 * (score)) - 6.79
probability of being stone-free =
= 1 / (1+EXP((-1) * X))
Performance:
• The area under the ROC curve is around 0.75.
