The Effect of the Body Mass Index and the Abdominal Circumference in the Diagnosis of Appendicitis using Ultrasonography

ABSTRACT

PURPOSE: This study was conducted to investigate the effect of body mass index (BMI) and abdominal circumference (AC) on the diagnosis of appendicitis using ultrasonography (US). METHODS: Between January 1, 2007, and June 30, 2007, we recruited 170 patients who complained about right lower-quadrant pain and who had an Alvarado score greater than 7 points. We recorded the height, weight, and AC for each patient and calculated a BMI. All patients received US investigation by emergency department residents. The cases were categorized according to whether the appendicitis was visible or non-visible. The sensitivity, specificity, and accuracy for each group were assessed and compared. RESULTS: A total of 170 patients was enrolled. Of those 94 patients had visible signs of appendicitis, and 76 patients had non-visible appendicitis. The mean BMI and AC of visible group were 22.09+/-3.12 and 77.47+/-9.32, as compared with 22.43+/-4.05 and 83.83+/-9.48 for the non-visible group, and the groups had significant differences in BMI and AC (p<0.001). The sensitivity, specificity and accuracy of US in patients with BMI under 25 were 58%, 60%, and 58%, respectively, and for those with BMI over 25 were 35%, 50%, and 36%. The sensitivity, specificity, and accuracy of US for male patients with AC under 90 cm were 55%, 75%, and 56%, and for those with AC over 90 cm the numbers were 35%, 50%, and 33%. The sensitivity, specificity, and accuracy of US in females with AC under 80 cm were 75%, 75%, and 74% and for those with AC over 80 cm, 45%, 50%, and 47%. CONCLUSION: Increasing BMI and AC negatively affect the US sensitivity, specificity, and accuracy in an appendicitis diagnosis.