Ultrasound and clinical features for differential diagnosis of low-grade appendiceal mucinous neoplasm and acute suppurative appendicitis.

Aim: To investigate the application of ultrasound along with clinical features for the differential diagnosis of low-grade appendiceal mucinous neoplasm (LAMN) and acute suppurative appendicitis (ASA).

Material and methods: The ultrasound and clinical data of 76 patients with histopathologically confirmed LAMN (31 patients) and ASA (45 patients) were retrospectively analyzed. Univariate analysis and binary logistic regression analysis of the influencing factors were conducted to identify LAMN and ASA. The AUROC was calculated to analyze the diagnostic efficacy of these independent factors. A four-grid table was established to determine the diagnostic efficacy of the ultrasound marks for diagnosing LAMN.

Results: Patient age and appendix short diameter in the LAMN group were found to be significantly higher than those in the ASA group. The neutrophil ratio and thickness of the appendix wall in the LAMN group were significantly lower than they were in the ASA group. Patient age (OR=1.112, p=0.015) and appendix short diameter (OR=1.476, p=0.008) were independent risk factors for LAMN. The AUROCs for age and short diameter were 0.898 [95% CI: 0.807, 0.956] and 0.953 [95% CI: 0.879, 0.988], respectively. The LAMN group tumors were characterized by the appearance of an "onion skin" sign or a purely cystic mark on sonograms, with specificities of 100% for both. Neutrophil ratio (OR<0.001, p=0.064) and thickness of the appendix wall (OR=0.776, p=0.414) were not independent risk factors for ASA.

Conclusion: Employing ultrasonography with clinical features is useful for distinguishing LAMN from ASA. Patient age, short diameter of the appendix, and sonographic appearance of "onion skin" or purely cystic mark could be key factors in diagnosing LAMN.