Neutrophil-to-lymphocyte ratio as a predictor of severity and adverse outcomes in complicated acute diverticulitis.

Complicated acute diverticulitis (CAD) requires accurate risk stratification to guide emergency management and surgical decision-making. Hemogram-derived inflammatory biomarkers, including the neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR), may provide rapid and accessible prognostic information. This study evaluated the diagnostic and prognostic utility of these biomarkers compared with the APACHE II score in patients with CAD. This retrospective study included 204 adult patients with CT-confirmed CAD treated at a tertiary referral center in Mexico between March 2022 and December 2024. Admission inflammatory biomarkers, including NLR, PLR, RDW, and WBC count, together with APACHE II score, were analyzed. Primary outcomes included disease severity (abscess versus peritonitis), need for surgery, postoperative complications, and in-hospital mortality. Receiver operating characteristic (ROC) curve analysis and multivariable logistic regression were performed. Most patients presented with severe disease, with peritonitis observed in 86.8% of cases. Mean NLR was significantly higher in patients with peritonitis, those requiring surgery, and non-survivors (p < 0.001). PLR was significantly higher in patients with abscesses (p = 0.008). ROC analysis demonstrated that NLR showed good discriminatory performance for peritonitis (AUC 0.758) and excellent performance for in-hospital mortality (AUC 0.962). In surgically treated patients (n = 177), APACHE II was the strongest independent predictor of major postoperative complications (OR 1.34; p < 0.001), whereas preoperative NLR remained an independent predictor of postoperative mortality (OR 14.54; p = 0.001). NLR is an inexpensive and widely available biomarker with strong prognostic performance in complicated acute diverticulitis. It may assist in early identification of patients at increased risk of severe disease, surgical intervention, and mortality. Combining CBC-derived inflammatory biomarkers with validated severity scoring systems such as APACHE II may improve emergency triage and perioperative risk stratification in CAD.