Nomogram and scoring system for predicting stone-free status after extracorporeal shock wave lithotripsy in children with urolithiasis.
OBJECTIVE
To determine the stone-free rate after extracorporeal shock wave lithotripsy (ESWL) and its associated factors to formulate a nomogram table and scoring system to predict the probability of stone-free status in children.


METHODS
A total of 412 children (427 renal units [RUs]) with urolithiasis were treated with ESWL using a lithotriptor between 1992 and 2008. Cox proportional hazards regression was used to model the number of treatment sessions to stone-free status as a function of statistically significant demographic characteristics, stones and treatment variables. A bootstrap method was used to evaluate the model's performance. Based on the multivariate model, the probabilities of being stone-free after each treatment session (1, 2 and >3) were then determined. A scoring system was created from the final multivariate proportional hazard model to evaluate each patient and predict their stone-free probabilities.


RESULTS
Complete data were available for 395 RUs in 381 patients. Of the 395 RUs, 303 (76.7%) were considered to be stone-free after ESWL. Multivariate analysis showed that previous history of ipsilateral stone treatment is related to stone-free status (hazard ratio [HR]: 1.49; P = 0.03). Stone location was a significant variable for stone-free status, but only in girls. Age (HR 1.65, P = 0.02) and stone burden (HR 4.45, P = 0.002) were significant factors in the multivariate model.


CONCLUSIONS
We believe that the scoring system, and nomogram table generated, will be useful for clinicians in counselling the parents of children with urolithiasis and in recommending treatment.
Department of Urology, Children's Hospital Boston, Harvard Medical School, USA.
Bulent
B
Onal
Nejat
N
Tansu
Oktay
O
Demirkesen
Veli
V
Yalcin
Lin
L
Huang
Hiep T
HT
Nguyen
Bartley G
BG
Cilento
Ahmet
A
Erozenci
D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D008096:Lithotripsy; D008297:Male; D015999:Multivariate Analysis; D049451:Nomograms; D012189:Retrospective Studies; D012720:Severity of Illness Index; D012737:Sex Factors; D016896:Treatment Outcome; D052878:Urolithiasis / Q000628:therapy*