Ultrasound Registry Review (URR) Abdomen Practice Exam

The main idea here is recognizing a characteristic ultrasound sign that points to a mucinous dilation of the appendix. Mucocele caused by mucinous material tends to fill and layer inside a dilated appendix, producing multiple concentric laminations that look like an onion on ultrasound. This onion-like, laminated appearance—often described as the onion sign—is highly characteristic for an appendiceal mucocele and helps distinguish it from simple fluid-filled structures.

Comet-tail is a reverberation artifact seen in other contexts and isn’t the typical feature of a mucocele. A simple anechoic tubular structure would suggest a straightforward fluid-filled channel without internal layering, which doesn’t reflect the mucinous content. The target sign can appear in other conditions such as intussusception and isn’t the defining feature of a mucocele.