Editorial Comment on: How Reliable Is the Intraoperative Assessment of Residual Fragments During Percutaneous Nephrolithotomy? A Prospective Study by Nevo et al.

This issue's article by Nevo and colleagues addresses the question of real versus perceived stone-free rates by urologists after a percutaneous nephrolithotomy (PCNL), an uncommonly studied phenomenon. Here, two surgeons gave their endoscopic impressions of the presence of significant residual calculi at the end of each PCNL, which were compared with stone size on postoperative imaging. Almost 20% of patients thought to be stone free were found to have significant residual fragments (RFs). Even when the surgeon performed flexible nephroscopy and fluoroscopy, large stone fragments were missed in almost one of five patients.

There is a concern that patients will have a subsequent stone event secondary to these RFs. A previous study by Raman and colleagues looking at patients post-PCNL showed that those with RF >2 mm were more likely to have a stone event. ¹ Fragment size after PCNL was again found to be predictive of stone events in a more recent study by our group. ² Thus, the most effective strategy for stone management would be to achieve complete stone-free status in patients. There has been some speculation that urologists may underestimate calculus size when examining endoscopically but a recent study found that endourologists in fact tend to overestimate stone size by 0.05 mm and are generally accurate within ±2 mm during ureteroscopy. ³ Thus, it would seem that these subsequently demonstrated fragments are entirely missed endoscopically intraoperatively. Postoperative imaging is, therefore, paramount, preferably with a noncontrast abdominal CT because of its superiority to plain X-ray and renal ultrasonography. Complete stone-free status and eliminating any fragments after PCNL are the best way to reduce future stone episodes.