Is computed tomography mandatory for the detection of residual stone fragments after percutaneous nephrolithotomy?

The introduction of minimally invasive endourologic procedures for upper urinary stone disintegration has closed the curtain on the era of open surgery for upper urinary tract stones in which complete stone eradication was the rule. This shift to minimally invasive procedures has led to the introduction of new terminology, such as stone-free rates and residual stone fragments, the presence of which after treatment was considered an acceptable therapeutic end point. Percutaneous nephrolithotomy (PCNL) is currently considered the procedure of choice for large renal stones. Its use has been greatly facilitated by the favorable profile of multidetector CT with regard to its sensitivity in detecting small stones. Despite the fact that CT is considered essential for the diagnosis and exact localization of stones and has been used for the creation of percutaneous tracts in PCNL, however, its routine use for the post-PCNL detection of residual stones has not been established. There is evidence that routine application of post-PCNL CT provides additional advantages compared with other imaging modalities-namely, the identification of the presence and location of even small residual fragments, which has been shown to cause significant trouble and necessitate secondary procedures in a significant cohort of patients after PCNL. On the other hand, the issues of cost, availability of CT scanners, and radiation exposure along with the acceptable sensitivity, cost, and availability of other imaging studies has raised doubts as to whether CT should be the routine imaging study after PCNL. The present review will discuss the concept of clinically significant residual fragments and comment on the advantages and drawbacks of different imaging studies used for the detection of residual stones after PCNL. This review also aims to clarify the indications in which CT should routinely be performed or could be omitted in the follow-up after PCNL.