Effects of pneumoperitoneum on postoperative atelectasis and Clara Cell Protein 16 levels in laparoscopic cholecystectomy

Background: This study aimed to evaluate the development of atelectasis in the postoperative period in patients undergoing laparoscopic cholecystectomy using lung ultrasonography and to investigate changes in Clara Cell Protein 16 (CCP16) levels. The objectives were to enable early recognition of postoperative lung injury through non-invasive methods, contribute to the prevention of complications, and assess the combined effectiveness of lung ultrasonography and biomarker use in clinical practice. Additionally, it was examined whether these parameters could provide complementary diagnostic value. Methods: This prospective observational study was conducted at Erzincan Mengücek Gazi Eğitim ve Araştırma Hastanesi with ethical committee approval and informed patient consent. A total of 91 patients aged 18–70 years, classified as ASA I–II and scheduled for elective laparoscopic surgery, were included. Morbidly obese patients, those with severe comorbidities, or those undergoing emergency surgery were excluded. Patients were allocated into two groups according to intra-abdominal pressure: Group L (n=44, 8–12 mmHg) and Group S (n=47, 12–15 mmHg). Demographic data, smoking history, and surgical/anesthesia duration were recorded. All patients underwent standardized anesthesia induction and maintenance. Intraoperative vital parameters were recorded at predefined time points. Lung ultrasonography was performed preoperatively (T1) and postoperatively (T2) using a 12-region modified scoring system. CCP16 levels were measured from venous blood samples taken preoperatively and postoperatively using the Reed Biotech Human CC16 ELISA kit. Results: Postoperative LUS scores increased significantly in both groups (p<0.001), with no significant difference in the extent of increase between groups (p=0.136). Postoperative LUS increase correlated positively with BMI in both Group L (p=0.039) and Group S (p=0.003), while age, gender, and smoking history showed no significant effect. Pneumoperitoneum duration correlated positively with LUS increase in Group S (p=0.047), whereas a nonsignificant positive trend was observed in Group L (p=0.096). CCP16 levels increased significantly in both groups postoperatively (p<0.001), with no intergroup differences in levels or increase (p=0.573). Correlation analysis showed a weak, non-significant negative association between LUS and CCP16 increases in Group L (p=0.404), and no relationship in Group S (p=0.772). Conclusions: Both low- and standard-pressure pneumoperitoneum during laparoscopic cholecystectomy were associated with significant postoperative increases in lung ultrasound scores and Clara Cell Protein 16 levels. However, pneumoperitoneum pressure did not influence the magnitude of these changes. The absence of correlation between LUS and CCP16 increases 14 suggests that they represent distinct dimensions of lung injury. Our findings reveal that the lungs are affected at both macroscopic and microscopic levels in laparoscopic cholecystectomies.