Nomogram for predicting complicated appendicitis and aiding decision-making regarding antibiotic therapy for acute appendicitis

Abstract Background Antibiotic therapy is a feasible treatment option for uncomplicated appendicitis, but the preoperative diagnosis of uncomplicated appendicitis is challenging. This study aimed to develop a nomogram to predict complicated appendicitis based on laboratory data and CT features and to guide antibiotic treatment decision-making. Methods Patients with pathologically confirmed acute appendicitis (AA) were randomly split into the primary and validation cohorts. The nomogram model for predicting complicated appendicitis was constructed based on the results of the multivariate logistic analysis in the primary cohort and transformed into a nomogram risk score. The nomogram was validated in a validation cohort and an independent antibiotic therapy cohort. Results A total of 375 patients were included in the primary cohort, 168 patients were included in the validation cohort, and 169 patients were included in the antibiotic treatment cohort. In the primary cohort, multivariate analysis confirmed that periappendiceal fat stranding (PFS, p < 0.001, OR = 67.80), the C-reactive protein level (CRP ≥ 38, p < 0.001, OR = 5.77) and the neutrophil-to-lymphocyte ratio (NLR ≥ 7, p < 0.001, OR = 3.51) were independent risk factors for complicated appendicitis. The PFS, CRP and NLR scores were 10.0, 4.0 and 3.0 points, respectively, based on the nomogram. Each patient was assigned a score obtained with the nomogram, called the nomogram risk score, and the best cutoff value for the nomogram risk score was 11.0 points. Fourteen patients (3.7%, 14/375) and seven patients (4.2%, 7/168) with complicated appendicitis were classified as having uncomplicated appendicitis in the primary and validation cohorts, respectively. When the nomogram risk score was greater than 11, the failure rate of antibiotic treatment was 49.2%; when the nomogram risk score was less than 11, the failure rate of antibiotic treatment was only 5.3%. Furthermore, the predictive accuracy of the nomogram risk score for antibiotic treatment failure as measured by the area under the curve (AUC) was 0.823 (95% CI: 0.757–0.878). Conclusion We found that the proposed nomogram risk score based on clinical and CT features not only enables the accurate identification of complicated appendicitis patients before surgery but also serves to guide management decisions.