Objective:

To systematically evaluate and quantitatively synthesize the associations of preoperative NLR and SII with postoperative pneumonia and pulmonary complications after lung resection or esophagectomy in the context of a systematic review and meta-analysis.

Key Findings:

• Eight retrospective cohort studies comprising 3,936 patients were included.
• Higher preoperative NLR and SII showed directionally consistent associations with increased postoperative pulmonary risk, but the certainty of evidence is low.
• Continuous analyses suggested a twofold increase in the odds of postoperative pneumonia per one-unit increment in NLR.
• Categorical analyses indicated an approximately fourfold increase in odds of pneumonia above study-specific thresholds for NLR.

Interpretation:

Limitations:

• The evidence base is small and exclusively retrospective.
• The studies are geographically concentrated.
• Hartung–Knapp confidence intervals crossed unity in three of the four pooled analyses, indicating low certainty of evidence.

Conclusion:

These low-cost immune-inflammatory indices require confirmation in larger, prospective studies before they can be considered for routine perioperative risk stratification.