Analysis of postoperative infection factors of retrograde intrarenal surgery combined with negative pressure equipment for renal stones

Our study aimed to retrospectively analyze the patients who underwent the combination of negative pressure equipment and RIRS(NP-RIRS) for renal stones, and identified new high-risk factors related to infection. 456 patients with renal stones ≤ 3 cm underwent NP-RIRS in our department, from January 2022 to October 2023. All patients were divided into non-infection group(NIRIRS group) and infection group(IRIRS group) based on infection complications during the perioperative period. Establish a receiver operating characteristic curve(ROC curve)based on variables with statistical differences, and use the Jordan index to find the optimal cutoff value. Classify the data into two categories based on the best truncation value, and perform binary logistic regression analysis on the classified data. In the IRIRS group, there were 10 cases of fever (2.92%), 2 cases of sepsis (0.58%), and no cases of septic shock or death. The length and the CT value of the stone were 16 (13,21) vs. 22 (19,24) (p < 0.001), 764 (570,1012) vs. 1372 (841,1527) (p < 0.001), respectively, and there was a statistical difference. The surgical time of NIRIRS group and IRIRS group were 57 (50,65) vs. 75 (60,98), respectively (p < 0.001), with statistical differences. On the contrary, the stone-free rate(SFR) at 3 months after surgery was 97.60% vs. 91.70% (p = 0.209), and there was no difference. The length of stones, surgical time, and CT values of stones between the two groups were further used to establish ROC, with ROC areas of 0.791, 0.791, and 0.816, respectively(Fig. 2). Based on the Jordan index, the optimal cutoff values were 17.5 mm (stone size), 64.5 min (surgery time), and 732.5 HU (stone CT value), respectively. Three continuous variables were transformed into binary data using the best truncation criterion, and the classified results were subjected to binary logistic regression analysis. The results showed that the three variables remained independent risk factors for postoperative infection complications. The incidence of infection after NPRIRS was lower than TRIRS for kidney stones. Length of stones, surgical time, and CT value of stones were independent risk factors for postoperative infection in NPRIRS treatment of kidney stones. Due to the small sample size, the credibility and generalizability of the conclusions were limited.