To compare the difference of indirect ultrasound signs by high and low frequency ultrasonography and to evaluate the value on the diagnosis of appendicitis.

The clinical data of one hundred and fifty-three patients with appendicitis admitted to Zhongshan City People's Hospital from January 2011 to May 2014 were retrospectively analyzed. The clinical symptoms and signs of the patients were atypical and they were examined by low and high frequency ultrasonography. The indirect ultrasound signs were analyzed and compared with pathology results and clinical follow-up.

The diagnostic accuracy of ultrasonography in 153 cases was 79.1% (121/153). There were 93 cases of simple appendicitis, 19 cases of appendiceal abscess, 32 of acute cellular appendicitis, 9 of acute gangrenous appendicitis, and the diagnosis was confirmed by pathology and follow-up. The low frequency and high frequency ultrasonography showed significant differences in the detection of indirect signs such as edema of ileocecal, enlargement of appendix and thickening of appendix wall (P<0.05). All of the Kappa values were greater than 0.8 in the coincidence test between the indirect signs of high-frequency ultrasound and the signs seen during surgery.

For appendicitis patients with atypical clinical symptoms and signs, high frequency ultrasonography can improve the detection rate, and improve the diagnostic accuracy of appendicitis when combined with low frequency ultrasound.