📃 Paper Title: Clearance of lower-pole stones following shock wave lithotripsy: effect of the infundibulopelvic angle
🧍 Author: F X Keely Jr
🕒 Year: 1999
📚 Journal: European Urology
🌎 Country: UK
ㅤContext to the study:
Can you tell me about a study that explores the effect of anatomic factors on stone clearance following shockwave lithotripsy (SWL)?
ㅤ✅ Take-home message of study:
To assess the effect of anatomic factors, including angle of lower pole infundibulum, for clearance using SWL of lower calyceal stones measuring 11-20mm.
The stone free rate was 52%
The only significant anatomical factor determining stone-free rate in this study was the infundibulopelvic angle.
The size of the stone did not predict eventual stone free status (p=0.911)
Patients treated with SWL for an 11-20mm stone who have an infundibulopelvic angle of >100 degrees are twice as likely to obtain stone free status.
Other factors to consider (although not significant in this study) are the infundibular diameter and calyceal distortion.
ㅤ Retrospective, single-centre study
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Study participants:
116 patients with single lower-pole stones measuring 11-20mm and treated with shock wave lithotripsy, chosen from a SWL database of over 8000 patients
Mean age 62 (16 - 80 years)
80 had stones on the left, 36 on the right
110 were treated on the Wolf 2300 piezoelectric lithotriptor and 11 on the Dornier MFL 9000 lithotriptor.
Exclusion criteria: abnormal renal anatomy (horseshoe, duplex) any pre-SWL treatment, including ureteral stents, the presence of infection-related or radiolucent stones or less than 6 months FU.
The mean follow-up length was 21 (range 6-108) month
The infundibular angle was measured by a urologist and radiologist independently, stone free rate was evaluated using FU KUB without PCNL.
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Key study outcomes:
Stone free rate of large (11-20mm) lower calyceal stones with SWL
52% (60/116) patients were stone free after SWL
35% had residual lower pole stones <4mm in size
22 patients required intervention following SWL, including 4 who needed PCNL to their original lower pole fragmented stone, 8 needed repeat SWL.
Factors affecting stone free status
The infundibulopelvic angle was the only factor to attain significance in predicting stone-free status (p = 0.012).
Two other factors (the absence of calyceal distortion and a large infundibular diameter) were associated with stone-free status, but did not reach statistical significance (p = 0.113 and p = 0.309, respectively)
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Study Limitations:
Single-centre study
Infundibular angle is not static but rather dynamic - diameter can change during peristalsis making measurements imprecise, no mention of standard error/deviation.
Retrospective analysis with a relatively small population.
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