Measurement of stone free rate after miniaturized percutaneous nephrolithotomy

Document Type: Editorial


Urology Research Center, Sina Hospital, Tehran University of Medical Sciences, Tehran, Iran



Stone free rate (SFR) after stone treatment modalities could be measured by plain radiography and ultrasonography, or computed tomography (CT) scan. Urology textbooks, mentioned that CT is the primary method for evaluation of residual stone fragments after PCNL (percutaneous nephrolithotomy) due to its high sensitivity and wide availability. But, there must be a balance with the need to minimize unnecessary radiation exposure in patients. On the other hand, Regarding MPCNL (miniaturized percutaneous nephrolithotomy), some studies showed that the actual SFR after MPNL might be overestimated, when relying on Ultrasound or X-ray control. Since CT scan achieved the highest sensitivity (93%) and specificity (97%) for the detection of kidney stones. Some authors define residual stones after MPCNL as larger than 3 millimetres, which cannot be detected by ultrasonography. Although we know that there are some concerns on radiation exposure in children using CT scan, we believe that small stone fragments after MPCNL are not vividly visible in ultrasound or x-ray. Thus, performing CT scan is more indispensable in MPCNL technique in order to detect small residual stone fragments. Finally, we believe that using CT scan in follow up of MPCNL patients, rather than plain radiography and ultrasonography, is more accurate to detect residual fragment and estimate SFR as one of the important outcomes of this operations.