Evaluation of radiological and temporal characteristics of acute appendicitis on the non-enhanced computed tomography images.

Purposes: To investigate the relationships and interactions between temporal and radiological features of gangrene and perforation of inflamed appendices.

Methods: A total of 402 patients were included who underwent laparoscopic appendectomies between January 1, 2016 and March 30, 2020 and had pathologically proved acute appendicitis and preoperative non-enhanced CT examinations. The radiological features (appendix diameter, appendicolith, appendiceal intraluminal gas, periappendiceal gas, periappendiceal fat stranding/fluid, and short axial diameter of the mesenteric lymph nodes) were obtained from the preoperative CT images of 382 patients with visible appendices. Clinical parameters and temporal variables (pre-CT delay, preoperative delay, estimated complication delay, symptom delay, and system delay) were recorded.

Results: Among simple/suppurative, gangrenous, and perforated appendicitis, the radiological characteristics except for short axial diameters of lymph nodes, and the temporal variables other than system delay were significantly different. The Cox regression analysis identified the appendicolith as the independent risk factor for both gangrene and perforation of inflamed appendices by using the preoperative delay or estimated complication delay. By the preoperative delay, the median time for gangrene and perforation was 76.23 (95%CI 73.89-78.58) h and 77.55 (95%CI 74.12-80.98) h, respectively, if appendicolith was present. If estimated complication delay was used as the elapsed time and the appendicolith was perceptible, the median time for gangrene and perforation and was 72.33 (95%CI 62.93-81.74) h and 75.07 (95%CI 69.48-80.65) h, respectively.

Conclusion: There were interactions between the time evolution and radiological features of acute appendicitis. The evaluation of gangrene and perforation rate of acute appendicitis could be benefitted from combining the preoperative delay/estimated complication delay with CT characteristics in the preoperative urgent radiological analysis.