To compare the efficacy and safety of minimally-invasive percutaneous nephrolithotomy (MPCNL) via middle and upper calyx approach in the treatment of upper urinary tract calculi in different positions (oblique supine lithotomy position and prone position), and to explore the advantages of clinical application of oblique supine lithotomy via middle and upper calyx approach.

Ninety-five patients who underwent ultrasound-guided MPNCL via the middle and upper calyx from March 2018 to May 2020 were selected and their clinical data were reviewed. They were divided into oblique supine group (49 cases, MPNCL via middle and upper calyx approach using oblique supine lithotomy position) and prone group (46 cases, MPNCL via middle and upper calyx approach using prone position) according to different positions of surgery. Perioperative parameters such as intraoperative postural comfort, changes in serum parameters, surgery-related complications, and one-time combined clearance rate and total stone clearance rate were compared.

There was no significant difference in gender, age, BMI, stone size, stone location, stone number, stone side, degree of hydronephrosis, preoperative complications, anatomical abnormalities and other baseline data between the two groups (all P>0.05). The overall intraoperative comfort in the oblique supine group was better than that in the prone group were (P<0.05); the channel establishment time, operation time and hospital stay in the oblique supine group were less than those in the prone group (all P<0.05); the hemoglobin change value, serum urea change value, serum creatinine change value and serum β2-microglobulin change in the oblique supine group were less than those in the prone group (all P<0.05); the incidence rate of surgery-related complications in the oblique supine group (12.2%) was lower than that in the prone group (32.6%) (P<0.05). The one-time stone clearance rate (89.8%) and total stone clearance rate (95.9%) in the oblique supine group were higher than those in the prone group (69.6%, 76.1%) (all P<0.05).

Compared with prone position, MPNCL via middle and upper calyx in oblique supine lithotomy position can effectively reduce intraoperative postural discomfort, reduce intraoperative blood loss, shorten operation time and reduce renal injury, which is beneficial to postoperative recovery, with less related complications, high stone clearance rate and high safety. It is an alternative nephrolithotomy position.