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Onal B et al, 2012: Nomogram and scoring system for predicting stone-free status after extracorporeal shock wave lithotripsy in children with urolithiasis

Onal B, Tansu N, Demirkesen O, Yalcin V, Huang L, Nguyen HT, Cilento BG, Erozenci A
Department of Urology, Children's Hospital Boston, Harvard Medical School, Boston, USA
Department of Urology, University of Istanbul Cerrahpasa Medical Faculty, Istanbul, Turkey.


Abstract

Study Type - Prognosis (cohort) Level of Evidence 2a What's known on the subject? and What does the study add? Extracorporeal shock wave lithotripsy is often considered to be the first-line treatment method for the majority of urinary tract stone disease in children. The stone clearance rate in children treated with ESWL is higher than that in adults. Recently, nomograms for several diseases, e.g. for specific cancers, have been developed and validated in large patient populations. They have become very popular predictive tools that provide the most objective, evidence-based, and individualized risk estimation. These nomograms have gained acceptance as useful guides in clinical practice for use by physicians and patients. In adults, a nomogram has been created to predict stone-free outcome after ESWL; however, to our knowledge none has been developed for children with urolithiasis. This is the first study-generated nomogram table and scoring system for predicting the stone-free rate after ESWL in children. This predictive tool could be useful for clinicians in counselling the parents of children with urolithiasis and in recommending treatment.

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.

PATIENTS AND 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.

CONCLUSION: 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.

© 2012 BJU INTERNATIONAL.
BJU Int. 2013 Feb;111(2):344-52. doi: 10.1111/j.1464-410X.2012.11281.x. Epub 2012 Jun 6
PMID: 22672514 [PubMed - as supplied by publisher]

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Comments 1

Hans-Göran Tiselius on Wednesday, 22 February 2012 07:45

The authors have developed a scoring system with the aim of predicting the stone-free rates in children treated with ESWL. Not unexpectedly the most important variables in that scoring system were the stone burden and the number of stones. Interestingly the stone-free rate was highest in the lowest age-group, but it is indeed surprising that as many as 90% of the children were treated with only sedation. The average stone-free rate in children is generally high and, as also stated by the authors, better than that in adults. It is therefore not clear how useful this scoring system (nomogram) will be in the clinical management of children for whom a non-invasive treatment approach in most situations is considered to be the method of choice.

Hans-Göran Tiselius

The authors have developed a scoring system with the aim of predicting the stone-free rates in children treated with ESWL. Not unexpectedly the most important variables in that scoring system were the stone burden and the number of stones. Interestingly the stone-free rate was highest in the lowest age-group, but it is indeed surprising that as many as 90% of the children were treated with only sedation. The average stone-free rate in children is generally high and, as also stated by the authors, better than that in adults. It is therefore not clear how useful this scoring system (nomogram) will be in the clinical management of children for whom a non-invasive treatment approach in most situations is considered to be the method of choice. Hans-Göran Tiselius
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