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Year : 2011  |  Volume : 27  |  Issue : 2  |  Page : 301-302

"Bonn Risk Index": The best predictor of calcium oxalate lithogenic potential in pediatric age

Department of Urology, C.S.M. Medical University (Upgraded King George's Medical College), Lucknow-226 003, Uttar Pradesh, India

Date of Web Publication8-Jul-2011

Correspondence Address:
Apul Goel
Department of Urology, C.S.M. Medical University (Upgraded King George's Medical College), Lucknow-226 003, Uttar Pradesh
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Source of Support: None, Conflict of Interest: None

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How to cite this article:
Dwivedi AK, Yadav R, Goel A. "Bonn Risk Index": The best predictor of calcium oxalate lithogenic potential in pediatric age. Indian J Urol 2011;27:301-2

How to cite this URL:
Dwivedi AK, Yadav R, Goel A. "Bonn Risk Index": The best predictor of calcium oxalate lithogenic potential in pediatric age. Indian J Urol [serial online] 2011 [cited 2021 Jul 31];27:301-2. Available from:

Porowski T, Kirejczyk JK, Zoch-Zwierz W, Konstantynowicz J, Korzeniecka-Kozerska A, Motkowski R, et al. Assessment of Lithogenic Risk in Children Based on a Morning Spot Urine Sample. J Urol 2010;184:2103-8.

   Summary Top

Estimating lithogenic potential of calcium oxalate stone formers can have wide potential regarding predicting risk of stone recurrence, metaphylaxis and monitoring medical treatment for stone disease. Laube et al, proposed a simple, cost-effective yet comprehensive parameter named "Bonn risk index" (BRI) for objective assessment of risk of calcium oxalate stone formation. [1] BRI is calculated as the ratio of [Ca ++ ] in mmol/L and the amount of (Ox--) in mmol that must be added to 200 ml of that sample to initiate crystallization. In adult stone formers, the value of BRI is usually >1.0/L. In pediatric stone formers, the median BRI has been reported to be several times higher (4.36/L), in comparison to healthy children (median 0.28/L). [2]

Standard BRI calculation is done from 24-hour urine sample. [3],[4] However, 24-hour urine collection is not only tedious but requires strong supervision or even hospitalization in case of pediatric age for accurate collection. Whether BRI of spot urine at particular part of day can be equally effective and could be surrogate for 24-hour collection was investigated in present study.

Forty-two children with history of calcium oxalate stone formation and 46 healthy children (suffering from nocturnal enuresis) as controls were hospitalized for 2 days. On the first day 24-hours urine was collected. On subsequent day, first urine was collected overnight (between 12 midnight and 6 a.m.) followed by every 2 hours (total of nine samples). Urine volume, urinary-free Ca ++ and oxalate ions required to initiate crystallization was measured in each urine sample. To calculate the BRI, onset of crystallization during titration with 40 mmol/L ammonium oxalate (Ox--) was detected using a photometer. Median BRI values for 24-hour urine collection in urinary stone formers and healthy subjects were 2.81/L and 0.28/L, respectively. Median BRI values obtained from each of the urine fractions in patients with urolithiasis were significantly higher than in controls. ROC curves revealed that urine after breakfast, collected in between 8 and 10 a.m., best separated stone-forming children from healthy controls. BRI calculated from this fraction had highest sensitivity and specificity even compared to 24-hour urine, which is considered the gold standard.

   Comments Top

Calcium oxalate stones are most common urinary stones in any age group. Its crystallization in urine depends not only on concentration product of free calcium and oxalate ions but also on urinary pH and concentration of crystallization inhibitor like citrate and Mg ++. Monitoring multiple factors via 24-hour urine every time is practically difficult. Drawbacks of 24-hour urine collection, beyond technical collection problem, are that peak value may be offset by value at trough and average value may not show risk potential. BRI represent a single, composite index which assesses all factors involved in calcium oxalate crystallization. Highest sensitivity and specificity of BRI in spot urine collected after breakfast in between 8 and 10 a.m. has obviated need for 24-hour urine collection. Introduction of computer-operated analytical system has made analysis of BRI spot urine less cumbersome and more accurate. [5] Practical application of results can make counseling of stone patients as well monitoring of medical management simplified and effective. Results need to be confirmed in other geographical region with different dietary habits before universalizing it.

   References Top

1.Laube N, Schneider A, Hesse A. A new approach to calculate the risk of calcium oxalate crystallization from unprepared native Urol Res 2000;28:274-80.   Back to cited text no. 1
2.Porowski T, Zoch-Zwierz W, Wasilewska A, Spotyk A, Konstantynowicz J. Normative data on the Bonn Risk Index for calcium oxalate crystallization in healthy children. Pediatr Nephrol 2007;22:514-20.  Back to cited text no. 2
3.Kavanagh JP, Laube N. Why does the Bonn Risk Index discriminate between calcium oxalate stone formers and healthy controls? J Urol 2006;175:766-70.  Back to cited text no. 3
4.Porowski T, Zoch-Zwierz W, Konstantynowicz J, Taranta-Janusz K. A new approach to the diagnosis of children's urolithiasis based on the Bonn Risk Index. Pediatr Nephrol 2008;23:1123-8.  Back to cited text no. 4
5.Porowski T, Mrozek P, Sidun J, Zoch-Zwierz W, Konstantynowicz J, Kirejczyk JK, et al. Bonn-Risk Index based micro-method for the assessment of the risk of urinary calcium oxalate crystallization. J Urol 2010;183:1157-62.  Back to cited text no. 5


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