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Alenezi H et al, 2015: The Effect of Renal Cysts on the Fragmentation of Renal Stones During Shockwave Lithotripsy: A Comparative In Vitro Study.

Alenezi H, Olvera-Posada D, Cadieux PA, Denstedt JD, Razvi H.
Division of Urology, Department of Surgery, Schulich School of Medicine and Dentistry, The University of Western Ontario , London, Ontario, Canada.
Department of Microbiology and Immunology, The University of Western Ontario , London, Ontario, Canada .
School of Health Sciences, Fanshawe College , London, Ontario, Canada.

Abstract: 

PURPOSE: To assess the potential effect of simple renal cysts (SRC) on stone fragmentation during shockwave lithotripsy (SWL) in an in vitro
model.

MATERIALS AND METHODS: The in vitro model was constructed using 10% ordnance gelatin (OG). Models were created to mimic four scenarios: Model A-with an air-filled cavity (suboptimal for stone fragmentation); model B-without a cavity (normal anatomy); model C-with a 3-cm serum filled cavity (to represent a small SRC); model D-with a 4-cm serum filled cavity (to represent a larger SRC). SWL was applied to 24 standardized phantom stones (weight of 2 ± 0.1 g) in each model using a standardized protocol. Stone fragments were retrieved, then dried overnight at room air temperature. Fragmentation coefficient (FC) was calculated for each stone, for fragments <4 mm and <2 mm.

RESULTS: The OG in vitro model was robust enough for the proposed research. There was no fragmentation evident in model A as expected. The mean FC was 29.7 (± 20.5) and 39.7 (± 23.7) for <4 mm fragments (P = 0.069) and 7.6 (± 4.1) and 10.6 (± 6.7) for <2 mm fragments (P = 0.047), for noncystic and cystic models, respectively. The mean FC was 29.7 (± 20.5), 38.8 (± 26.2) and 40.7 (± 21.3) for <4 mm fragments (P = 0.213) and 7.6 (± 4.1), 11.1 (± 8) and 10.2 (± 5.3) for <2 mm fragments (P = 0.138), for models B, C, and D, respectively.

CONCLUSION: Our in vitro experiment confirms better stone fragmentation associated with SWL in the presence of adjacent SRC.

J Endourol. 2015 Oct 9. [Epub ahead of print]

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Comments 1

Hans-Göran Tiselius on Wednesday, 13 April 2016 11:17

In this experimental gelatine model the authors studied SWL-induced stone disintegration under conditions mimicking the presence of renal cysts. Artificial stones were used together with serum-filled cavities, the latter representing cysts.

Storz Medical Modulith F2 lithotripter was used in the experiments and the fragmentation was expressed as a fragmentation coefficient (FC).

http://storzmedical.com/images/blog/Alenezi_H.png

The reason would be that SW propagation in serum is better than in the gel medium. This might correspond to a better SW transmission when cysts are in the shockwave path. Whether this experimental finding is of clinical importance for SWL of stones in kidneys with cysts is likely, but remains to be demonstrated. Anyway it has been shown that the presence of a cyst does not negatively influence the SW power.

A note of caution needs to be added, however, because in several cases the presence of a cyst can obstruct the calyx neck and hinder fragment elimination. Such patients might benefit from cyst puncture before SWL.

In this experimental gelatine model the authors studied SWL-induced stone disintegration under conditions mimicking the presence of renal cysts. Artificial stones were used together with serum-filled cavities, the latter representing cysts. Storz Medical Modulith F2 lithotripter was used in the experiments and the fragmentation was expressed as a fragmentation coefficient (FC). [img]http://storzmedical.com/images/blog/Alenezi_H.png[/img] The reason would be that SW propagation in serum is better than in the gel medium. This might correspond to a better SW transmission when cysts are in the shockwave path. Whether this experimental finding is of clinical importance for SWL of stones in kidneys with cysts is likely, but remains to be demonstrated. Anyway it has been shown that the presence of a cyst does not negatively influence the SW power. A note of caution needs to be added, however, because in several cases the presence of a cyst can obstruct the calyx neck and hinder fragment elimination. Such patients might benefit from cyst puncture before SWL.
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