Place of non contrast thin-slice spiral computed tomography in evaluation of stone-free ratio after percutaneous nephrolithotomy.

PURPOSE: To search the place of non contrast abdominal computed tomography to detect the stone-free rate after percutaneous nephrolithotomy (PNL) and the clinical importance of its superiority against to plain film radiography (KUB).
MATERIALS AND METHODS: Between February 2006 and July 2010, 62 patients including 27 women had no stone detected peroperative fluoroscopy and nephroscopy during PNL were included. Patients whom stone was not detected under 5 mm section upper abdomen non contrast spiral CT and KUB control in postoperative day 3 were defined as Group 1; patients whom stone was detected in a single slice CT were defined as clinically insignificant fragment (CIF)(Group 2) and patients whom stone was detected at least in two slice were defined as rest fragment (Group 3).
RESULTS: Median stone size were 22.3 mm (19-37 mm). Preoperative stone localization of groups were upper calyx, middle calyx, pelvis, lower calyx and 2.1, 14.9, 25.5 and 57.4%, respectively. CIF was detected in postoperative CT control of 12 (25.5%) patients whom stone was not followed in KUB and rest fragment was detected in 6 (12.8%) patients. Three of patients whom rest fragment was detected required an additional intervention for stone.
CONCLUSION: KUB which is routinely used to determine stone-free ratio after PNL operation is not sufficient to detect rest calculi and/or CIF existence in 38.3% patients. But when it is considered that most of rest stones detected were CIF and only 6.3% patients had additional intervention required rest calculi. We can think that CT follow-up is not absolutely required.