Interesting topic of discussion and I wonder what the usual plan is at your facilities with regard to US “equivocal and cannot see the appendix”. Apparently, we order too many CTs after that result, and might want to think about an alternative to radiation: observation period. According to one of our Radiology colleagues who is a guru with US, Dr Brooke Jeffrey, and studied this extensively with a goal to minimize radiation: 400 pediatric and adult patients had US to evaluate for appendicitis. 140/400 (35%) had either a normal (80 patients, 25%) or abnormal appendix (60 patients, 15%); 260/400 (65%) had non-visualization of the appendix. Overall there were 75 patients with appendicitis (18.8%) and 17 (4.3%) with perforation. Of the 260 patients with non-visualization of the appendix, 14 patients (5.4%) had appendicitis and 2 were perforated (0.8%). The prevalence of perforated and non-perforated appendicitis in this group was significantly lower than the overall group (p<0.001 and p<0.01, respectively). Of these 260 patients, 101 patients (38.8%) had CT within 48 hours and 79 (78.2%) had normal scans.
Are we scanning too many?…. I think so…. the low risk patient (by Alvarado score or your own clinical judgement) – why not observe them instead of getting the satisfaction of a diagnosis (or lack thereof…)? Look out for his article in the Journal of Clinical Ultrasound coming out in print sometime in the future ( you know, however quickly research goes to print after acceptance – like a year maybe :)
Here’s another study results, done at Stanford by Dr. Jeffrey: 385 consecutive patients with RLQ pain and US ordered. Among all 385 patients, 84 (21.8%) had appendicitis on initial ultrasound of which 12 (3.1%) had sonographic findings of perforation. Of these 385 patients, 334 (86.8%) had non-visualization of the appendix on initial ultrasound examination. Of these 334 patients with sonographically nonvisualized appendices, CT disclosed appendicitis in 46 (14%; p=0.005) of which 8 (2.4%; p=0.557) had CT evidence of perforation. CT provided alternate diagnoses for 15 (4.5%) of the 334 patients, 2 (0.6%) of which required immediate surgical intervention. CT was completely normal for 273 (81.7%) of the 334 patients. Since I doubt that those with a positive finding on CT would be included in a “low risk” category, we should start observing these patients, not going straight to CT… my 2 cents