Feasibility and safety of tract dilation under ultrasound guidance in standard percutaneous nephrolithotomy

Objective To investigate the feasibility of tract dilation monitored by ultrasound in percutaneous nephrolithotomy (PCNL), and the risk factors for its failure. Methods A retrospective study was conducted on patients underwent PCNL with only one access (F24) using balloon dilator and sequential dilators (Amplatz and telescopic metal dilators) from December 2014 to December 2018 in Beijing Tsinghua Changgung Hospital. A total of 231 patients (130 males and 101 females) underwent ultrasound-guided PCNL with a mean age of (52.3±9.8) years were included in our study. Mean BMI was (25.8±3.1)kg/m2. Mean size of stone was (3.9±1.1)cm, 51.1% (118/231) of which were staghorn stones. Under ultrasound guidance, after puncture of the target calyx, the balloon dilator was advanced through the guide wire, and inflated to establish the F24 standard renal access. Patients’ clinical parameters such as age, gender, BMI, stone diameter, history of open nephrolithotomy were collected. Risk factors for the failure of ultrasound guided balloon dilation were analyzed by logistic regression analysis. Results Tract dilation succeed in 89.2 % cases (206 succeed, 25 failed) at first attempt. Median tract dilation time was 4.2 min (2.2-8.0 min). Mean operation time was 85.5 min(45.0-120.0 min). Median hemoglobin drop at the first postoperative day was 16.0 g/L (5.0-25.8 g/L). The total rate of complication was 9.1% (21 cases), including 18 cases Clavien Ⅰ and 3 cases Clavien Ⅱ. The stone free rate was 89.6%(207/231). Logistic regression analysis revealed that lower pole access (P=0.014) was a risk factor for the failure of access establishment, while the presence of hydronephrosis of target calyx (P<0.001) would significantly increase the success rate. Conclusions Tract dilation using balloon catheter can be safely monitored by ultrasound with high success rate and low complication rate. Lower pole puncture will make tract establishment difficulty. Patients with a hydronephrotic target calyx are more suitable for this procedure. Key words: Kidney calculi; Percutaneous nephrolithotomy; Ultrasound guidance; Balloon dilation