Correlation between visceral and subcutaneous fat assessed by automated CT segmentation of abdominal fat and acute appendicitis in children

To automatically segment abdominal adipose tissue using the TotalSegmentator model in a Python environment based on CT images, and to explore the correlation between abdominal fat distribution and acute appendicitis in children. A retrospective review was performed on 6364 children with appendicitis admitted to our hospital from June 2015 to June 2025. Among them, 1319 patients had complete clinical and abdominal CT data, and 631 patients were enrolled into the acute appendicitis group after screening according to inclusion and exclusion criteria. Acute appendicitis was categorized as uncomplicated appendicitis ( n = 373) and complicated appendicitis ( n = 258). A total of 551 age-matched individuals with normal abdominal CT findings during the same period were recruited as the control group. Basic clinical data were collected, and the volumes of visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) at the midpoint of L1 ~ L5 vertebral bodies were measured using the CT-based automatic segmentation model. Fat distribution was compared between the acute appendicitis group and the control group, as well as between subgroups of different pathological types of acute appendicitis. Multivariable logistic regression was used to evaluate the independent associations of VAT volume and SAT volume with the risk of acute appendicitis, and with the progression to complicated appendicitis. In unadjusted analyses, VAT and SAT volumes were higher in the acute appendicitis group than in the control group ( p < 0.001). VAT and SAT volumes were higher in patients with uncomplicated appendicitis than in those with complicated appendicitis ( p < 0.001). Multivariable logistic regression demonstrated that older age, elevated neutrophil percentage, and elevated high-sensitivity C-reactive protein (hs-CRP) were independently associated with increased odds of acute appendicitis (OR = 1.3117, 1.0515, 1.0174, all p < 0.001). VAT volume was independently associated with increased odds of acute appendicitis only in children aged 2 ~ 6 years (OR = 1.0126, p = 0.0251). Higher neutrophil percentage and higher hs-CRP were independently associated with increased odds of complicated appendicitis (OR = 1.0317, p = 0.0058; OR = 1.0219, p < 0.001). Older age and larger SAT volume were independently associated with reduced odds of complicated appendicitis (OR = 0.8726, p = 0.0017; OR = 0.9985, p = 0.0135). According to multivariable logistic regression results, SAT volume was not associated with the onset of acute appendicitis in children, whereas increased SAT volume was independently associated with reduced odds of inflammatory progression to complicated appendicitis. The association between VAT volume and acute appendicitis was age-dependent: VAT volume was independently associated with higher odds of acute appendicitis in children aged 2 ~ 6 years, while no statistically significant association was observed in the 6 ~ 12-year and 12 ~ 18-year subgroups. VAT volume was not associated with the occurrence of complicated appendicitis in children.