**4. Results**

Overall success rate of uncomplicated nephrostomy tube placement is over 97% with less success in patients who required percutaneous tract for subsequent endourologic interventions. Factors which affect the success rate of nephrostomy tube placement during endourologic operation are stone burden, degree of hydronephrosis, history of previous open nephrolithotomy, and experience of surgeon. As same as other urologic procedure, a training simulator for ultrasound-guided percutaneous nephrostomy insertion is needed for a safe, non-threatening environment, without risk to patients. Commercial and a gelatin phantoms are available. Skill is required prior to undertaking procedures in patients. (Rock et al., 2010)
