MRI vs. ultrasound for suspected appendicitis during pregnancy

To compare the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of ultrasound (US) and MRI in evaluation of pregnant patients with a clinical suspicion of appendicitis.

A total of 33 pregnant patients with suspected appendicitis underwent US and MRI. The original imaging reports generated at the time of presentation were used for data analysis. Pathology reports were used for disease confirmation in patients who underwent appendectomy. When surgery was not performed, a medical record review was performed. The sensitivity, specificity, PPV, and NPV were calculated for US and MRI in the diagnosis of appendicitis.

Five of the 33 patients had pathologically-proven appendicitis. Four of the five patients with appendicitis were correctly diagnosed at MRI while one was interpreted as indeterminate (appendix not seen). At US, one was correctly diagnosed, one was incorrectly diagnosed as normal, and three were interpreted as indeterminate (appendix not seen). In 13 patients, a normal appendix was diagnosed at MRI, none of whom had appendicitis. In three patients, a normal appendix was diagnosed at US, one of whom had appendicitis. When the appendix was visualized at MRI, the sensitivity, specificity, PPV, and NPV for the diagnosis of appendicitis was 100% for all parameters. When the appendix was visualized at US, the sensitivity, specificity, PPV, and NPV for the diagnosis of appendicitis was 50%, 100%, 100%, and 66%, respectively.

Based on a relatively small number of true-positives, our data suggests that MRI is very useful for the diagnosis and exclusion of appendicitis in pregnant women.