POCUS: How to Diagnose Appendicitis Using Ultrasound

1.    Place the patient supine
2.    Place the probe over the point of maximal tenderness in the RLQ or ask the patient to place the probe at the most painful site.
3.   Use “graded compression” until landmarks are visualized – the right psoas (P) muscle and the iliac vessels (Ia and Iv) – and/or appendix, which will appear as a blind-ended pouch. The appendix is found either in between these structures and/or anterior to these structures.

• Graded compression moves gas and bowel out of the plane of the ultrasound bringing the appendix closer to the abdominal wall, making it more easily visualized.

4.     Once visualized, confirm that it is indeed the appendix by visualizing it in both the transverse and longitudinal plane; the appendix should be a blind-ending tubular structure.

Longitudinal

Longitudinal

Transverse

Transverse

5.  Measure the appendix and compress. A normal appendix is < 6 mm in diameter (<6  to 7 mm described in some literature for pediatrics) from outer wall to outer wall and compressible.(2)

In a non-cooperative child (or adult) who is in pain, consider analgesia before starting and distraction, such as with entertaining videos with a smartphone.(3)

For a short video summarizing the point of maximal tenderness technique and also introducing the “mini-lawnmower” technique, check out: http://5minsono.com/Appy/

1.     Outer diameter greater than 6 to 7 mm*
2.     Non-compressible (Note: it might be compressible in perforation)
3.     Lack of peristalsis

Abnormal appendix in long view, measuring 8 mm in diameter

Abnormal appendix measuring 8 mm in diameter in transverse view surrounded by free fluid, consistent with appendicitis.  

Note that the literature usually uses a cut-off of 6 to 7 mm; however, infants may have a smaller diameter, with growth of the appendix reported at ages 3 to 6 years.  This highlights the need to look for secondary findings of appendicitis, especially in pediatric patients who may have a normal appendiceal diameter. (3) 

1. Appendicolith within the lumen, appearing as a hyperechoic structure with shadowing

2. Fluid surrounding the appendix appearing as hypoechoic material, representing edema or perforation

3. Increased vascularity visualized using color-flow Doppler

4. Wall thickness > 3 mm

5. Target Sign: hypoechoic center (fluid) surrounded by hyperechoic ring (mucosa/submucosa),surrounded by hypoechoic ring in axial view

6. Increased echogenicity of adjacent periappendiceal fat/omentum(4)

7. Enlarged mesenteric lymph nodes

8. Thickening and hyperechogenicity of overlying peritoneum

9. Dilated, hypoactive small bowel

10. Thickening of apical cecal pole or adjacent small bowel 

 Don’t worry you aren’t the only one.  Here are a few other techniques for you to try on your patients suspected of having acute appendicitis.  The following systematic approach has been described by Sivitz (5):

1. Move the probe laterally, identifying the ascending colon and lateral abdominal wall.

• The ascending colon is a non-peristalsing structure containing gas and fluid, or ‘dirty shadowing.’ You can also visualize haustra as you follow the colon down to the cecum.

2. Move down the lateral border into the cecum
3. Move medially across the psoas and iliac vessels

4,5. With the psoas muscle and iliac vessels kept in view, move the transducer down into the pelvis and toward the umbilicus at the border of the cecum

6. If the appendix is not yet visualized, place the probe in the sagittal position, identify the cecum in the long axis and sweep medially compressing the cecum against the psoas muscle 

What if you still cannot visualize the appendix? Perhaps the appendix is retrocecal. In one study(6) visualization of the appendix was improved 21.5% by following a 3-step technique.

1. 1. The first step is the usual supine technique as described above.

1. 1. Place the patient in a 45º left posterior oblique (LPO) position and scan parasagittally through the R flank in a coronal plane parallel to long axis of the psoas muscle. The appendix will appear anterior to the psoas muscle on the screen. (6)

1. If the appendix is still not visualized, the patient is returned to the supine position for a repeat attempt with the supine technique.

To visualize the LPO position: http://radtechsociety.blogspot.com/2012/11/anatomical-body-positions.html

Another troubleshooting technique is to place the left hand dorsally to the RLQ (essentially placing the hand on the patient’s back). The user then pushes against the patient’s back with anterior and anteromedial pressure with the 4 fingers of the hand; this technique improved visualization by 10% in one study.(7)

You’ll never know if you don’t try! Go ahead and put that probe on the abdomen and try to evaluate for appendicitis.

You won’t find it or hone in on your skills unless you give it a shot. If you see findings concerning for appendicitis, this can further support a clinical picture for appendicitis. However, do not utilize POCUS alone as a rule-out and instead consider your other resources available to you, such as serial abdominal exams, CT, MRI, and comprehensive ultrasonography by your radiology department.