What is the most sensitive marker of acute appendicitis on ultrasound?
Diameter > 6 mm (positive predictive value of 98%).
What does it mean if the appendix was not visualised?
Acute appendicitis still cannot be excluded but it does reduce the likelihood. If an appendix is not seen the negative predictive rate is 90% in one study.
A blind diverticulum arises from the caecum, presumably the appendix. It is thick-walled (measuring up to 8 mm), aperistaltic and hyperaemic. Small volume of surrounding free fluid. The patient was maximally tender over this point.