Zhong W et al, 2013: Percutaneous nephrolithotomy for renal stones following failed extracorporeal shockwave lithotripsy: different performances and morbidities
Zhong W, Gong T, Wang L, Zeng G, Wu W, Zhao Z, Zhong W, Wan SP
Department of Urology, Minimally Invasive Surgery Center, The First Affiliated Hospital of Guangzhou Medical College, Guangzhou, Guangdong, China
The purpose of this study is to summarize the results of percutaneous nephrolithotomy (PCNL) for renal stones following failed extracorporeal shockwave lithotripsy (SWL), and to investigate the effect of previous SWL on the performances and morbidities of subsequent PCNL. Sixty-two patients with a history of failed SWL who underwent PCNL on the same kidney (group 1) were compared to 273 patients who had received PCNL as first treatment choice (group 2). Patient demographics, stone characteristics, operative findings, and complications were documented and compared. Groups 1 and 2 had similar patient demographics and stone characteristics. Mean time to establish access was comparable in both groups (10.5 ± 4.2 vs. 9.6 ± 4.5 min, p = 0.894). Time required to remove stones and total operative time were longer in group 1 (71.5 ± 10.3 vs. 62.3 ± 8.6 min, p = 0.011 and 95.8 ± 12.0 vs. 80.6 ± 13.2 min., p = 0.018, respectively). Group 1 had lower clearance rate compared to group 2 (83.9 vs. 93.4 %, p = 0.021), while postoperative complications were similar in both groups. Scattered stone fragments buried within the tissues made the procedure more difficult for stone fragmenting and extracting, which lead to longer operative time and inferior stone free rate. However, the PCNL procedure was safe and effective in patients with failed SWL. The risk of complications was similar and clearance rate was encouraging.
Urolithiasis. 2013 Apr;41(2):165-8. doi: 10.1007/s00240-013-0545-z. Epub 2013 Feb 3
PMID:23503879 [PubMed - in process]
"Scattered stone fragments buried within the tissues..." Are these the effects of ESWL that can be seen during secondary PNL?
In 2009 Yuruk et al. (Yuruk E et al. Does previous extracorporeal shock wave lithotripsy affect the performance and outcome of percutaneous nephrolithotomy? J Urol 2009; 181:663–667) where the first to report on EWSL effects seen during secondary PNL. They only mentioned them in the discussion but not in the results section: "Our current experience shows that patients undergoing PNL after unsuccessful ESWL may have some nonspecific and subjective nephroscopy findings, such as fragile tissues, bruised calices and white membranes in the pelvicaliceal spaces." The time interval between ESWL and PNL was 3.5 ±2.1 months (range 1 to 12 months). At the time of PNL their patients had a stone size of 6,8 ±5,3 (1.5–25) cm2 after unsuccessful ESWL. This shows that EWSL was in initially not indicated in many cases because of a too large stone size. In 2010 Resorlu et al. (Resorlu B et al. (2010) Effect of previous open renal surgery and failed extracorporeal shockwave lithotripsy on the performance and outcomes of percutaneous nephrolithotomy. J Endourol 2010; 24:13–16) did not see similar findings in their series with an obviously smaller mean stone size of 5.1±2.7 cm2. They quote of course Yuruk et al. as the first reporting on ESWL effects.
In the present publication the authors mention a misuse of ESWL in the introduction: "Due to easy access to low-cost treatment, rampant overuse and misuse of SWL was seen in non-academic settings and under developed regions. Many patients with failed SWL were referred to our institution for further treatment." This might be the reason why large stones were treated with ESWL. The stone size was given in cm 3.8 ± 0.7 (2.1–5.3) cm and not in cm2 like in the other two publications. The stones could have been relatively large if height and width were identical. In fact they were even larger than in the group with primary PNL although not statistically significant.
The authors state "repeated SWL contributed to fibrous degeneration and distortion of collecting system over the long term" quoting Yuruk, Resorlu and a French group. In the result section they state" Forty-five cases (72.6 %) had stone fragments embedded beneath the pelvi-calyceal mucosa" And they discuss " In addition, pressure waves, especially after repeated procedures, could push stone fragments closer to renal mucosa, and the inflammatory hyperplasia tissue would imbed stone fragments. Yuruk and co-workers  showed that, the patients who underwent PCNL after failed SWL had nonspecific but noticeable changes, such as more fragile tissue, bruised calyces and membranous changes in the pelvicaliceal system. In this series, contracted calyceal infundibulum and embedded stone fragments beneath the pelvicaliceal mucosa were noticed in patients with failed SWL. ... Extracting stone fragments buried beneath the mucosal tissue required forceful digging and grasping, which was time consuming". The mechanism of fragment incorporation in the renal tissue is difficulty to understand and has not been described experimentally. I am not aware of studies showing that ESWL of stones will push fragments into tissue.
Obviously also in this study ESWL was initially not indicated and large partially fragmented stones were in situ for a long time period which obviously caused inflammatory changes and may be calcifications.