Miheler DA. et al., 2026: Factors influencing extracorporeal shockwave lithotripsy efficiency in the management of lower pole stones.

Miheler DA, Reman T, Gherasim R, Vida OÁ, Porav-Hodade D, Mártha O.
Med Pharm Rep. 2026 Jan;99(1):64-69. doi: 10.15386/mpr-2913

Abstract

Objectives: The low efficacy of extracorporeal shock wave lithotripsy (ESWL) in the treatment of lower pole stones is well known; the parameters which influence this effect are still under debate: patient age, stone size, presence of double J stent, body mass index (BMI), and radiological parameters of the lower calyx, such as infundibulopelvic angle (IPA), infundibulum length (IL), and width (IW) of patients and the skin-stone size.

Methods: We studied the effectiveness of extracorporeal shock wave lithotripsy (ESWL) in the treatment of lower calyx stones. All patients were investigated by uro-CT or intravenous urography (IVU), or kidney, ureter, bladder (KUB) radiography to confirm the diagnosis. J stents were inserted before therapy in 64 (18.6%) renal units. Factors affecting success, stone-free rate and complications were analyzed. We measured the skin-stone distance (SSD) of the lower calyx on 39 uro-CT image data, and infundibulum length, width and infundibulopelvic angle on 31 intravenous urography (IVU).

Results: Our retrospective study (between 2021 and 2024) included a total of 344 patients who underwent ESWL for lower calyceal stone (172 men, 172 women) with an average stone size 9.093±2.829 mm. 68.605% of patients became stone-free after the first ESWL session. The average skin stone distances measured in 0°, 45°, 90° angles were 96.5 ± 24.92 mm. Using the Chi-square test, we concluded that previously stented patients had a statistically lower stone-free rate (SFR) than those without a stent. (p=0.0078). The body mass index (BMI) of patients also influenced the SFR, as calculated with an Unpaired t-test and Welch correction (p = 0.002). We did not find any statistically significant differences between skin-stone sizes of patients with or without successful stone fragmentation (p=0.1147), and infundibulum length (p=0.07), infundibulum width (p=0.7681), and infundibulopelvic angle (p=0.996).

Conclusions: Single ESWL sessions often fail to achieve stone fragmentation and elimination, as this study shows. The success of ESWL sessions can be affected by the anatomical position of the stone, a lower pole kidney stone, the presence of pre-procedural double J stenting, and obesity.

Comment Hans-Göran Tiselius

The problem with residual fragments after SWL of lower pole stones is well recognized. Gravitation is considered a major factor together with other properties associated with the anatomy and geometry of the lower pole.

In the current study of 344 patients the stone-free rate was 68%. The SSD (skin to stone distance) did not affect the outcome, neither did the infundibular length, infundibular width or infundibulo-pelvic angle. BMI had an influence on the result and so did the presence of an internal stent.

How the authors selected their patients is not described, but it is of note that 96% (!!) of the stones were composed of COD and only 3.5% of COM.

Although different studies have come to different results in stone-free rates after SWL of lower pole stones, it stands to reason that lower pole stones deserve special consideration.

The outcome of treating lower pole stones is determined first by disintegration accomplished with SWL and second by factors that can increase elimination of residual fragments.

Urologists solve that problem in different ways by using inversion therapy of different kinds, propulsion therapy and burst wave lithotripsy. The purpose of all these methods is to maintain a non-invasive or least invasive stone removal methodology. Others select more invasive procedures such as RIRS or PCNL.

In the reviewer’s opinion too little effort has been spent on non-invasive fragment elimination after SWL. The unique property of SWL is its non-invasiveness and accordingly this technique should be combined with non-invasive methods for fragment elimination.

Hans-Göran Tiselius