[Appendicitis versus nonspecific acute abdominal pain: diagnostic accuracy of ultrasound]

The aim of this study is to assess the diagnostic accuracy of ultrasound to differentiate appendicitis from nonspecific acute abdominal pain, that is the most common process requiring differential diagnosis in clinical practice.

Patients admitted for suspicion of appendicitis were prospectively evaluated in our hospital during two years (2013-2014). Cases of nonspecific acute abdominal pain and appendicitis assessed by ultrasound were enrolled in the study. The different variables collected were statistically analyzed by descriptive, univariate and diagnostic accuracy studies.

A total of 275 patients were studied, 143 cases of nonspecific acute abdominal pain and 132 cases of appendicitis. Ultrasound sensitivity and specificity to differentiate appendicitis were 94.7% and 87.4% respectively, with a 12.6% rate of false positives and a 5.3% rate of false negatives. The rate of false negatives in perforated group was 17.4% and analysis according to Pediatric Appendicitis Score risk groups showed a 12.2% rate of false positives in low-risk group and a 6.3% rate of false negatives in high-risk group.

The use of ultrasound in low clinical probability cases of appendicitis could rise unnecessary surgery rate, due to the significant number of false positives in this group of patients. In high probability clinical cases, ultrasound does not contribute too much to diagnosis and it could be a confusion factor by the significant number of false negative associated to perforated appendicitis.