5. Appendix Ultrasound

Appendicitis Ultrasound Findings

  • Non-compressibility of the appendix (unless perforated)
  • Blind ended pouch
  • Diameter of the appendix > 6 mm
  • Single wall thickness ≥ 3 mm
  • Target sign
  • Hyperechoic appendicolith with posterior shadowing
Appendicitis Ultrasound with Target Sign and Dilated
Dilated appendix with a diameter >6mm and “Target Sign”
Appendicitis Ultrasound Long Axis Blind Ended Pouch
Dilated appendix with blind ended Pouch
Appendicitis Ultrasound Appendicolith Fecolith
Appendicolith in an appendix with a diameter > 6cm.
5. Appendix Ultrasound

Option 1: Point of Maximal Tenderness

This is our preferred method when you strongly suspect appendicitis based on your patient’s history and physical exam.

Have your patient point, as precisely as possible, to “where it hurts” – the point of maximal tenderness.

  • Place the probe on the point of maximal tenderness with the indicator towards the patient’s right.
  • Attempt to locate the appendix as a non-compressible structure with a blind-ended pouch.
  • Rotate the probe to attempt to find the appendix in long and short-axis views.
  • Look for the signs of Appendicitis on Ultrasound described below.

Option 2: Systematic Approach

If you prefer a more organized approach, try starting in the RUQ, again with the probe in the transverse orientation with the indicator facing the patient’s right.

  • Trace the ascending colon downward until reaching the cecum, and have identified the psoas major and the iliac vessels, as seen below.
  • Now, search slightly medial to the psoas muscle for the ultrasound findings of appendicitis described below.
Appendix Appendicitis Ultrasound Sliding Ascending Colon
Sliding down the Ascending Colon to look for the Appendix with Ultrasound
Appendix Appendicitis Landmark Psoas Muscle and Iliac Artery Ultrasound
Landmarks for Appendicitis on Ultrasound – Psoas Muscle and Iliac Artery (IA)

Tip: if bowel gas is obscuring the image, use graded compression, and watch the patient’s eyes for any signs of discomfort as you apply pressure. The appendix can be especially difficult to visualize in patients with a large habitus. Keep in mind that the appendixes can be retrocecal, thus will be obscured from view when there is gas in the ascending colon.

5. Appendix Ultrasound

Appendicitis Ultrasound Protocol

Acute appendicitis is the most common abdominal emergency, representing 250,000 cases annually, and a lifetime prevalence among men and women of 9% and 7%, respectively (Mostbeck).

However, diagnosing appendicitis is a challenge, despite its prevalence. Symptoms are often non-specific, overlapping with various abdominal pathologies. And finding the appendix can be tricky, especially since the appendix can be located retrocecally.

This makes ultrasound less sensitive (~84%) for detecting appendicitis – failing to identify the appendix does not exclude it.

The most common presenting symptom of appendicitis is abdominal pain. The pain starts as dull periumbilical pain, then localized about a day later as sharp, stabbing pain at McBurney’s point, or 1/3 the distance of a line drawn between the anterior superior iliac spine and the umbilicus.

McBurney's Point - Appendicitis Appendix
McBurney’s Point

There are two ways to go about the appendix POCUS exam, described below. We recommend starting with the “point of maximal tenderness” method, then using a more systematic approach to finding the appendix if the first method isn’t successful.

First, position your patient and select your probe.

  • Probe selection: linear probe for a child/thin adult, or curvilinear probe for any patient with a large BMI.
  • Preset: Superficial/Abdomen
5. Appendix Ultrasound

Appendix Ultrasound

As one of the most common conditions prompting an ED visit, appendicitis is a pathology you are certain to encounter. And it’s a pathology you certainly don’t want to miss, given the complications associated with perforation.

Indications for performing an ultraosund exam of the appendix include the following common signs and symptoms:

  • Focal RLQ pain
  • Rebound tenderness/signs of peritoneal irritation
  • Pelvic pain
  • Fever
  • Elevated WBC count

The appendix is located in the right lower quadrant, attached to the cecum. However, its location can vary widely in its anatomic position, as pictured below.

Appendix/Appendicitis locations