Use of Vertebra and Iliac Bone as References in Localization of Vermiform Appendix in Computed Tomography

Objectives:The vermiform appendix may assume variable anatomical positions, which can impact the diagnosis of acute appendicitis.As computed tomography (CT) is widely used for evaluation, minimizing radiation exposure is essential.This study aims to determine the typical appendix location in the general population, using CT, and to define bony reference points-vertebral levels and the right iliac crest-which may enable field of view limitation and contribute to radiation dose reduction.Methods: Between January 2015 and January 2018, abdominal CT scans of 427 patients with abdominal pain were retrospectively analyzed.The appendix origin (Ap0), highest point (ApA), and lowest point (ApB) were measured relative to vertebral levels and the right iliac crest.The appendix course was classified as ascending or descending.The study used statistical analysis with t-test, chi-square, and Pearson correlation, considering p<0.05 as significant.Results: Among 427 patients (48.2% female, mean age 42.119.5;range 18-90), the appendix had an ascending course in 90.4% of cases.The measurement of the ApA ranged from L2 to the coccyx, with values between +87.4 mm and -140.5 mm relative to the right iliac crest.Acute appendicitis was present in 15.9% of the patients and confirmed surgically.In these cases, the origin and ApA were significantly higher (p=0.04),while the ApB did not differ (p=0.19).Ap0 was lower in females (p=0.03).Vertebral levels correlated weakly with age, height, and BMI. Conclusion:The appendix location in adults was defined using vertebral and iliac bone references.It was most commonly located at the L5-S1 and S1 levels.On average, the origin was 41 mm below the right iliac crest, the ApA was 23 mm below, and the ApB was 60 mm below the right iliac crest.While vertebralbased levels varied with age, height, and BMI, iliac-based measurements remained stable.These findings may help limit CT scan range and reduce radiation exposure in suspected appendicitis.