The correct initial diagnostic imaging test to evaluate pediatric abdominal pain for appendicitis is an ultrasound. It carries none of the risks associated with CT imaging – except for the increased risk of a non-diagnostic evaluation. It is also highly operator dependent and suffers in centers without sufficient volume of abdominal ultrasonography.
This study evaluates the subset of ultrasonography reports with the dreaded result “Appendix not visualized.” Overall, 37.7% of 662 consecutive ultrasonographic studies at the authors’ institution failed to visualize the appendix. Of interest to these authors were the “secondary signs” of appendicitis – free fluid, pericecal inflammatory changes, prominent lymph nodes, and phlegmon.
Their results are quite complicated – and, woefully, not terribly helpful. Free fluid in females – useless. Free fluid in males – more helpful if there’s a lot, but still only 2 cases of appendicitis out of the 5 males with a moderate/large amount of free fluid. Lymph nodes – useless. Pericecal fat changes – 1 out of 4. Phlegmon – 2 out of 2.
So, there’s some information here. Secondary signs with “Appendix not visualized” are typically not diagnostic alone – but, depending on the summation of other clinical findings, may yet be enough to obviate supplemental CT.
“Appendix Not Seen: The Predictive Value of Secondary Inflammatory Sonographic Signs”
www.ncbi.nlm.nih.gov/pubmed/23528502