US may be used for the evaluation of suspected appendicitis in adults with a pooled sensitivity of 83% (95% confidence interval [CI], 78%-87%) and a pooled specificity of 93% (95% CI, 90%- 96%), as shown in a meta-analysis of 31 studies with 4,341 patients. In the meta-analysis, CT demonstrated a higher pooled sensitivity of 94% (95% CI, 92%-95%) and a similar specificity of 94% (95% CI, 92%-95%) in that study [50]. In low pretest probability populations, a negative or equivocal US for appendicitis can be used with confidence to exclude this condition without the need for further imaging, with an NPV of 100% and 96%, respectively. However, in cases of moderate or high pretest probability of acute appendicitis and equivocal US, the sensitivity of the US falls to 63% and, thus, should not be solely used to exclude appendicitis [66]. A combination of abdominal US and clinical features successfully predicted uncomplicated appendicitis in 94% of 678 patients in a retrospective cohort study [67]. Evaluation for appendicitis with graded compression of the appendix increases specificity and decreases negative appendectomy rates, as shown in a retrospective study of more than 1,000 patients, with a sensitivity of 83%, a specificity of 100%, and a negative appendectomy rate of 8.4% [68]. Evaluation of renal stones with US is limited. A study of 50 patients demonstrated a sensitivity of 52% to 57% in the right kidney and 32% to 39% in the left kidney when compared with CT for detection of renal stones by US. This study also showed no significant impact of body mass index on the detection of renal stones [69]. A multicentric study of 144 patients showed that in 75% of cases, the presence or absence of hydronephrosis on US correctly predicted the presence or absence of a ureteral stone on CT. Hydronephrosis on US had a PPV of 77% for the presence of a ureteral stone and an NPV of 71% for the absence of a ureteral stone [70].
Acute Pelvic Pain in the Reproductive Age Group. US may be used for the evaluation of suspected appendicitis in adults with a pooled sensitivity of 83% (95% confidence interval [CI], 78%-87%) and a pooled specificity of 93% (95% CI, 90%- 96%), as shown in a meta-analysis of 31 studies with 4,341 patients. In the meta-analysis, CT demonstrated a higher pooled sensitivity of 94% (95% CI, 92%-95%) and a similar specificity of 94% (95% CI, 92%-95%) in that study [50]. In low pretest probability populations, a negative or equivocal US for appendicitis can be used with confidence to exclude this condition without the need for further imaging, with an NPV of 100% and 96%, respectively. However, in cases of moderate or high pretest probability of acute appendicitis and equivocal US, the sensitivity of the US falls to 63% and, thus, should not be solely used to exclude appendicitis [66]. A combination of abdominal US and clinical features successfully predicted uncomplicated appendicitis in 94% of 678 patients in a retrospective cohort study [67]. Evaluation for appendicitis with graded compression of the appendix increases specificity and decreases negative appendectomy rates, as shown in a retrospective study of more than 1,000 patients, with a sensitivity of 83%, a specificity of 100%, and a negative appendectomy rate of 8.4% [68]. Evaluation of renal stones with US is limited. A study of 50 patients demonstrated a sensitivity of 52% to 57% in the right kidney and 32% to 39% in the left kidney when compared with CT for detection of renal stones by US. This study also showed no significant impact of body mass index on the detection of renal stones [69]. A multicentric study of 144 patients showed that in 75% of cases, the presence or absence of hydronephrosis on US correctly predicted the presence or absence of a ureteral stone on CT. Hydronephrosis on US had a PPV of 77% for the presence of a ureteral stone and an NPV of 71% for the absence of a ureteral stone [70].