Planning percutaneous nephrolithotomy using multidetector computed tomography urography, multiplanar reconstruction and three-dimensional reformatting

OBJECTIVE: To assess a modified technique of multidetector computed tomographic urography (CTU) which can reproducibly and accurately map the pelvicalyceal system (PCS) and complex renal calculi, as such information is essential in choosing the optimal percutaneous approach into the PCS for safe and successful percutaneous nephrolithotomy (PCNL). PATIENTS AND METHODS: Ten consecutive patients with renal calculi underwent a modified four-detector multislice CTU with frusemide, abdominal compression and subsequent injection with contrast medium. After unenhanced CT of the abdomen, a high-resolution contrast-enhanced scan was taken through the kidneys in the pyelographic phase. Data were analysed using multiplanar reconstruction and three-dimensional (3D) reformatting. RESULTS: In 10 CTUs there were three staghorn, two diverticular, 25 calyceal, two infundibular and two renal pelvic calculi; nine showed posterior calyces and good infundibular anatomy, and provided a good map of the PCS. Seven patients had PCNL, with the remaining three having either primary extracorporeal shock wave lithotripsy or conservative management. CTU detected stones in all patients and accurately located their relation to the PCS. With reconstructed images, subjectively the 3D imaging provided an advantage over conventional imaging in optimizing nephrostomy placement. CONCLUSION: CTU with this protocol and post-processing techniques enables an accurate and confident, reproducible prediction of the site, number and size of stones in complex pelvicalyceal anatomy, optimal site(s) for placing the percutaneous track, and potential hazards when placing the track, with no significant increase in the patient's radiation burden. 3D CTU should become the standard imaging method for planning PCNL in selected patients.