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El-Assmy A et al, 2015: Risk factors for formation of steinstrasse after extracorporeal shock wave lithotripsy for pediatric renal calculi: a multivariate analysis model.

El-Assmy A, El-Nahas AR, Elsaadany MM, El-Halwagy S, Sheir KZ.
Urology and Nephrology Center, Urology Department, Mansoura University, Mansoura, Egypt.

Abstract

OBJECTIVES: To define various stone, renal and therapy factors that could affect steinstrasse (SS) formation after extracorporeal shock wave lithotripsy (SWL) for pediatric kidney stones. Thus, SS could be anticipated and prophylactically avoided.
METHODS: From January 1999 through December 2012, 317 children underwent SWL with Dornier Lithotripter S for the treatment of renal stones. Univariate and multivariate statistical analyses of patients, stones and therapy characteristics in relation to the incidence of SS were performed to detect the factors that had a significant impact on SS formation.
RESULTS: The overall incidence of SS was 8.5 %. The steinstrasse was in the pelvic ureter in 74.1 % of the cases, lumbar ureter in 18.5 % and iliac ureter in 7.4 %. Steinstrasse incidence significantly correlated with stone size, site and age of child. Steinstrasse was more common with increasing stone length and stones located in renal pelvis or upper calyx with the age below 4 years. A statistical model was constructed to estimate the risk of steinstrasse formation accurately. The equation for logistic regression is Z = -4.758 + B for age + B for size stone X length in mm + B for stone site.
CONCLUSIONS: The stone size, site and age are the most important risk factors responsible for SS formation in children. Our regression analysis model can help with prospective identification of children who will be at risk of SS formation. Those children at high risk of SS formation should be closely monitored or treated by endoscopic maneuvers from the start.

Int Urol Nephrol. 2015 Apr;47(4):573-577. Epub 2015 Mar 4.

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Comments 1

Peter Alken on Tuesday, 26 May 2015 07:26

A retrospective study on 317 children treated in 12 years with ESWL monotherapy with no auxiliary procedures. Stone analysis and actual stone sizes are not given.

“The logistic regression model showed that the odds ratio for SS formation had increased 1.1-fold for each 1-mm increase in stone length, and in comparison with children >4 years, younger children have 2.6-fold increase in SS formation. In comparison with stones in the middle calyx, the odds ratio of SS formation had increased 2.9- and 2.6-fold for stones in the upper calyx and pelvis, respectively.”

Stone size is a naturally accepted parameter of the risk of SS formation. But why should a stone in the middle calyx carry the lowest risk of SS formation and why is this location consequently taken as reference location in the logistic regression calculation. Age as a factor is explained by the fact that children ≤4 years are less actively walking. Did the authors know that between 12 and 24 months > 90 % of all children are walking?

Shaking the data of a retrospective study will eventually generate statistically significant differences. This only signifies associations but not causations.

A retrospective study on 317 children treated in 12 years with ESWL monotherapy with no auxiliary procedures. Stone analysis and actual stone sizes are not given. “The logistic regression model showed that the odds ratio for SS formation had increased 1.1-fold for each 1-mm increase in stone length, and in comparison with children >4 years, younger children have 2.6-fold increase in SS formation. In comparison with stones in the middle calyx, the odds ratio of SS formation had increased 2.9- and 2.6-fold for stones in the upper calyx and pelvis, respectively.” Stone size is a naturally accepted parameter of the risk of SS formation. But why should a stone in the middle calyx carry the lowest risk of SS formation and why is this location consequently taken as reference location in the logistic regression calculation. Age as a factor is explained by the fact that children ≤4 years are less actively walking. Did the authors know that between 12 and 24 months > 90 % of all children are walking? Shaking the data of a retrospective study will eventually generate statistically significant differences. This only signifies associations but not causations.
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