Abstract
I read with great interest the article titled “Management of Anteriorly Located Renal Caliceal Stones with Two Different Techniques (Mini-Percutaneous Nephrolithotomy vs.Flexible Ureteroscopic Laser Lithotripsy): A Critical Comparative Evaluation of the Outcomes.” 1 The study provides valuable insights into the efficacy and safety of these two minimally invasive techniques. The findings highlight that mini-percutaneous nephrolithotomy (mini-PCNL) achieves higher stone-free rates for lower caliceal stones compared with flexible ureteroscopic laser lithotripsy (fURS), albeit with longer operative times and increased postoperative complications. On the contrary, fURS appears safer and more suitable for stones in the middle and upper anterior calices. I hope to offer additional perspectives based on the International Alliance of Urolithiasis (IAU) consensus on this topic.
First, the IAU consensus recommends the term “miniaturized PCNL (mPCNL)” as the standardized nomenclature, rather than “mini-PCNL,” to ensure uniformity in clinical practice and academic communication. 2 This terminology helps avoid the confusion caused by previously used terms such as Chinese minimally invasive percutaneous nephrolithotomy, mini-PCNL, minimally invasive percutaneous nephrolithotomy, micro-percutaneous nephrolithotomy, ultra-mini percutaneous nephrolithotomy, and super-mini percutaneous nephrolithotomy, while emphasizing the use of miniaturized instruments and downsized sheaths to distinguish it from standard percutaneous nephrolithotomy. In addition, the consensus defines mPCNL as procedures performed with sheaths no larger than 18 Fr, emphasizing its potential to reduce renal trauma and complications. I would recommend that future studies consider adopting this standardized terminology to align with the international expert consensus and enhance clarity in communication.
Second, while the use of sheaths no larger than 18 Fr in mPCNL is effective for stone clearance, concerns about elevated renal pelvic pressure (RPP) during the procedure remain. In the approach described in this study, utilizing a 16 Fr mini nephroscope with an 18 Fr sheath may heighten these risks due to inadequate outflow, especially in cases involving prolonged operative times or substantial irrigation demands. To address these concerns, smaller-caliber instruments, such as 8/9.8 Fr ureteroscopes, could be considered as an alternative. 3 Although this may compromise the operator’s convenience and efficiency, it offers the advantage of maintaining lower RPP, reducing the risk of complications, and minimizing reliance on additional equipment.
Lastly, the introduction of vacuum-assisted flexible ureteroscopic sheaths has marked a significant advancement in fURS, enabling the maintenance of lower intrarenal pressure and leading to improved outcomes for complex caliceal stones. 4,5 However, certain challenging scenarios, such as calyceal diverticular stones, remain difficult to manage. When the calyceal neck is hard to identify by fURS, mPCNL offers a significant advantage with its precise access. 6 To further advance this field, future prospective studies are encouraged to explore and compare the applications of fURS and mPCNL in managing calyceal diverticular stones.
Sincerely,
Xin Zhu