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Anglada-Curado et al, 2012: Extracorporeal shock wave lithotripsy for distal ureteral calculi: Improved efficacy using low frequency

Anglada-Curado FJ, Campos-Hernández P, Carrasco-Valiente J, Anaya-Henares F, Carazo-Carazo JL, Alvarez-Kindelán J, Regueiro-López JC, Requena-Tapia MJ
Department of Urology, Reina Sofia Hospital, Córdoba, Spain


Abstract

OBJECTIVES: To compare low versus high frequency for lithotripsy in the management of distal ureteral calculi.

METHODS: A total of 154 patients with radio-opaque calculi (0.5-1 cm diameter) in the distal ureter were randomized to be given either lithotripsy at 80 or 60 pulses per min (high frequency or low frequency groups, respectively). The number of waves and sessions received, and time to total resolution were measured. A Dornier Compact Delta lithotripter was used.

RESULTS: A total of 72 patients were assigned to the high frequency group and 78 to the low frequency group. Four patients were excluded from the study because of intolerance of the procedure. The size was slightly lower in low frequency group, whereby an analysis of covariance was carried out to eliminate the size factor, with the limit established as 0.7 cm. The low frequency group received 2980 ± 1211 waves, and the high frequency group received 5752 ± 3121 (P < 0.001). The success rate was higher in the low frequency group (100%) than in the high frequency group (92.9%; P = 0.02). If adjusted to the size of the calculus with a threshold of 0.7 cm, there was a difference, although it was not statistically significant. The time to elimination of the fragments was higher in the high frequency group (17.68 days) than in the low frequency group (7.15 days; P < 0.001). The number of sessions necessary for resolution was higher in the high frequency group (1.56) than in the low frequency group (1.14; P < 0.001).

CONCLUSIONS: Lithotripsy at 60 pulses provides better outcomes than lithotripsy at 80 pulses for the treatment of distal ureteral calculi.

© 2012 The Japanese Urological Association.
Int J Urol. 2012 Sep 12. doi: 10.1111/j.1442-2042.2012.03133.x. [Epub ahead of print]
PMID: 22970896 [PubMed - as supplied by publisher]

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Comments 1

Hans-Göran Tiselius on Monday, 30 April 2012 07:10

In a study that compares shockwaves administered at frequencies of 80 and 60 (1.33 and 1.00 Hz), the authors conclude that the lower rate was associated with better treatment outcome for distal ureteral stones. This finding is in line with several previous reports on the importance of the shockwave frequency, but in this series of treatments there is an unusually narrow interval; 80 vs. 60 shockwaves per minute. This report is, however, particularly interesting because the authors have used the assumed benefit of a low shockwave rate and accordingly set the upper number of shockwaves at a lower level than that used for patients treated with the higher frequency. This is important inasmuch as a better disintegration should lead to a reduced total energy.

The major problem for proper interpretation of the result was the difference in stone size with stones measuring > 7 mm in 64% of the high-frequency group but only in 40% of the low-frequency group.

It is highly desirable that future studies on the possible advantages of low-frequency ESWL clearly report to which extent the treatment time (that is the total number of shockwaves) can be reduced.

Hans-Göran Tiselius

In a study that compares shockwaves administered at frequencies of 80 and 60 (1.33 and 1.00 Hz), the authors conclude that the lower rate was associated with better treatment outcome for distal ureteral stones. This finding is in line with several previous reports on the importance of the shockwave frequency, but in this series of treatments there is an unusually narrow interval; 80 vs. 60 shockwaves per minute. This report is, however, particularly interesting because the authors have used the assumed benefit of a low shockwave rate and accordingly set the upper number of shockwaves at a lower level than that used for patients treated with the higher frequency. This is important inasmuch as a better disintegration should lead to a reduced total energy. The major problem for proper interpretation of the result was the difference in stone size with stones measuring > 7 mm in 64% of the high-frequency group but only in 40% of the low-frequency group. It is highly desirable that future studies on the possible advantages of low-frequency ESWL clearly report to which extent the treatment time (that is the total number of shockwaves) can be reduced. Hans-Göran Tiselius
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