Quantitative analysis of pleural effusion after prone percutaneous nephrolithotomy based on routine postoperative abdominal computed tomography: prevalence, risk factors, and clinical implications.

Background: Detailed analysis of post-percutaneous nephrolithotomy (PCNL) pleural effusion (PE) and its relationship with respiratory symptoms is lacking. This study quantitatively investigates the prevalence, volume, and clinical significance of post-PCNL PEs detected on abdominal computed tomography (CT). Methods: We conducted a retrospective analysis of 252 consecutive patients who underwent prone PCNL between January 2018 and April 2020. PEs and stone volume were quantified using three-dimensional (3D) segmentation of post- and pre-operative abdominal CT images, respectively. Respiratory symptoms were categorized as asymptomatic, mild, moderate, or severe based on vital signs and complaints documented in nursing records. Zero-inflated Gaussian models were used to analyze effusion volume, whereas ordinal regression analyses were employed to identify predictors of symptom severity. Results: The incidence of post-PCNL PE was 77.0%, with a mean volume of 31.8 mL [95% confidence interval (CI): 27.8-36.3]. Most patients (69.8%) were asymptomatic, yet 4.0% experienced severe symptoms, with only 1.2% requiring drainage. Notably, 27.8% of PE was not mentioned in radiology reports. PE volume showed moderate positive correlation with respiratory symptom severity (r=0.44, 95% CI: 0.33-0.53, P<0.001). A volume cutoff of 51.24 mL was identified as predictive of moderate-to-severe symptoms [area under the curve (AUC) =0.86, 95% CI: 0.78-0.93]. Supracostal puncture [odds ratio (OR) =2.02, 95% CI: 1.04-3.93; P=0.038], post-operative lymphocyte counts (OR =0.46, 95% CI: 0.25-0.87; P=0.016), and activated partial thromboplastin time (OR =1.11, 95% CI: 1.01-1.23; P=0.035) were significantly associated with PE occurrence. Although supracostal puncture was associated with greater PE volume (β=0.334, 95% CI: 0.071-0.597; P=0.013), postoperative lymphocyte count was associated with lower volume (β=-0.310, 95% CI: -0.577 to -0.043; P=0.023). Effusion volume (OR =1.02, 95% CI: 1.02-1.03; P<0.001) predicted respiratory symptom severity, whereas higher post-operative total protein levels (OR =0.94, 95% CI: 0.89-0.99; P=0.017) were associated with milder symptoms. Conclusions: Post-PCNL PE is common but frequently asymptomatic and under-reported in radiology reports. Clinical management should be tailored based on PE volume, supracostal puncture, and post-operative total protein levels, independent of stone burden. Enhanced awareness among radiologists may improve detection and reporting of this common complication.