Abstract
<title>Abstract</title> <p>Acute diverticulitis in immunologically compromised patients has been associated with worse outcomes, although the independent contribution of immunological status beyond radiological severity remains uncertain. This study evaluated the association between high-risk immunological status and conservative management failure after adjusting for radiological severity and explored a prognostic model. A retrospective multicenter cohort study included patients with CT-confirmed acute diverticulitis (Hinchey IA–IV) treated at three tertiary centers in Mexico between January 2020 and December 2024. The primary analysis assessed the association between high-risk immunological status (WSES grade ≥ 1) and failure of initial conservative management using Firth penalized logistic regression. Internal validation was performed with bootstrap resampling. Of 170 patients, 134 (78.8%) received conservative treatment, with failure in 36 (26.9%). Failure increased with Hinchey stage: IA 2.9%, IB–II 43.9%, and III–IV 100%. After adjustment for Hinchey classification, high-risk immunological status was not independently associated with failure (adjusted OR 1.90; 95% CI 0.71–5.08). The model showed good discrimination (optimism-corrected AUC 0.765) and calibration (Brier score 0.128). Radiological severity was the strongest predictor of conservative management failure, while the effect of immunological status was largely explained by more severe radiological presentation. External validation is required.</p>