Body mass index, pain score and Alvarado score are useful predictors of appendix visualization at ultrasound in adults.

The study objective was to find factors predictive of ultrasound visualization of the appendix in patients with suspected appendicitis. A total of 238 consecutive adult patients (178 women, mean age 38.9 y, weight 58.2 kg, body mass index 22.7) who underwent appendiceal ultrasound from January to December 2011 were included. Appendicitis was confirmed in 171 patients (171/238, 71.9%). Ultrasound sensitivity, specificity and accuracy were 64%, 90% and 71%, respectively. The appendix was visualized at ultrasound in 126 patients (group 1) and not visualized in 112 patients (group 2). Group 1 had a lower body mass index, higher pain score and higher Alvarado score. The chances of visualizing the appendix in patients with body mass indexes ≤22, pain scores ≥6, and Alvarado scores ≥6 were 2.3, 2.9, and 3.8 times higher than those of their counterparts, respectively. Therefore, in patients with these factors, the use of ultrasound may be beneficial in the diagnosis of acute appendicitis.