References

1. Guan L, Liu Z, Pan G, Zhang B, Wu Y, Gan T, Ouyang G. The global, regional, and national burden of appendicitis in 204 countries and territories, 1990–2019: a systematic analysis from the Global Burden of Disease Study 2019. BMC gastroenterology. 2023 Feb 22;23(1):44.
2. Wickramasinghe DP, Xavier C, Samarasekera DN. The worldwide epidemiology of acute appendicitis: an analysis of the global health data exchange dataset. World Journal of Surgery. 2021 Jul;45:1999-2008.
3. Hamill JK, Liley A, Hill AG. Historical aspects of appendicitis in children. ANZ journal of surgery. 2014 May;84(5):307-10.
4. Ferris M, Quan S, Kaplan BS, Molodecky N, Ball CG, Chernoff GW, Bhala N, Ghosh S, Dixon E, Ng S, Kaplan GG. The global incidence of appendicitis: a systematic review of population-based studies. Annals of surgery. 2017 Aug 1;266(2):237-41.
5. https://emergencycarebc.ca/clinical_resource/suspected-appendicitis-in-children/
6. Schneider C, Kharbanda A, Bachur R. Evaluating appendicitis scoring systems using a prospective pediatric cohort. Annals of emergency medicine. 2007 Jun 1;49(6):778-84.
7. Cundy TP, Gent R, Frauenfelder C, Lukic L, Linke RJ, Goh DW. Benchmarking the value of ultrasound for acute appendicitis in children. Journal of pediatric surgery. 2016 Dec 1;51(12):1939-43.
8. Lee SH, Yun SJ. Diagnostic performance of emergency physician-performed point-of-care ultrasonography for acute appendicitis: A meta-analysis. Am J Emerg Med. 2019;37(4):696-705. doi:10.1016/j.ajem.2018.07.025
9. Matthew Fields J, Davis J, Alsup C, et al. Accuracy of Point‐of‐care Ultrasonography for Diagnosing Acute Appendicitis: A Systematic Review and Meta‐analysis. Mark Courtney D, ed. Acad Emerg Med. 2017;24(9):1124-1136. doi:10.1111/acem.13212
10. Cho SU, Oh SK. Accuracy of ultrasound for the diagnosis of acute appendicitis in the emergency department: A systematic review. Medicine (Baltimore). 2023;102(13):e33397. doi:10.1097/MD.0000000000033397
11. Scheier E, Shapira Levy E, Fisher A. POCUS for pediatric appendicitis in the pediatric emergency department: An 8‐year retrospective review. J Clin Ultrasound. 2024;52(9):1355-1359. doi:10.1002/jcu.23813
12. Kasmire K, Davis J. Emergency Department Point‐of‐Care Ultrasonography Can Reduce Length of Stay in Pediatric Appendicitis: A Retrospective Review. J Ultrasound Med. 2021;40(12):2745-2750. doi:10.1002/jum.15675
13. Pogorelic Z, Rak S, Mrklic I, Juric I. Prospective validation of Alvarado score and Pediatric Appendicitis Score for the diagnosis of acute appendicitis in children. Pediatric emergency care. 2015 Mar 1;31(3):164-8.
14. Sağ S, Basar D, Yurdadoğan F, Pehlivan Y, Elemen L. Comparison of appendicitis scoring Systems in Childhood Appendicitis. Turkish Archives of Pediatrics. 2022 Sep;57(5):532.
15. Kharbanda AB, Vazquez-Benitez G, Ballard DW, Vinson DR, Chettipally UK, Kene MV, Dehmer SP, Bachur RG, Dayan PS, Kuppermann N, O’Connor PJ. Development and validation of a novel pediatric appendicitis risk calculator (pARC). Pediatrics. 2018 Apr 1;141(4).
16. Sivit CJ. Diagnosis of acute appendicitis in children: spectrum of sonographic findings. AJR. American journal of roentgenology. 1993 Jul;161(1):147-52.
17. Jeffrey Jr RB, Laing FC, Townsend RR. Acute appendicitis: sonographic criteria based on 250 cases. Radiology. 1988 May;167(2):327-9.
18. Goldin AB, Khanna P, Thapa M, McBroom JA, Garrison MM, Parisi MT. Revised ultrasound criteria for appendicitis in children improve diagnostic accuracy. Pediatric radiology. 2011 Aug;41:993-9.
19. Rioux M. Sonographic detection of the normal and abnormal appendix. AJR Am J Roentgenol. 1992;158(4):773-778. doi:10.2214/ajr.158.4.1546592
20. Quigley AJ, Stafrace S. Ultrasound assessment of acute appendicitis in paediatric patients: methodology and pictorial overview of findings seen. Insights Imaging. 2013;4(6):741-751. doi:10.1007/s13244-013-0275-3
21. Sivitz AB, Cohen SG, Tejani C. Evaluation of acute appendicitis by pediatric emergency physician sonography. Annals of emergency medicine. 2014 Oct 1;64(4):358-64.
22. Borbély Márton. Appendicitis ultrasound [Internet]. Wikimedia Commons; July 6, 2024. Available from: https://commons.wikimedia.org/wiki/File:Appendicitis_ultrasound.png.

Summary

• Ultrasound is the diagnostic method of choice in pediatrics for appendicitis, and POCUS can provide rapid, real-time assessment.

• The appendix position varies, making it challenging to locate, especially in retrocecal or pelvic positions.

• Begin with the point of maximal tenderness, then use anatomical identification and graded compression to improve visualization.

• If the appendix is found, scan in both short and long axes and apply color Doppler to assess vascularity and inflammation.

• Dilation of the appendix >6mm, along with secondary findings such as wall thickening, hypervascularity, free fluid, echogenic fat, lymphadenopathy, and the presence of an appendicolith are key findings confirming appendicitis.

• PoCUS for appendicitis should be used as a rule-in test, where a positive result supports the diagnosis—helping guide immediate management decisions, but a negative scan alone does not reliably rule it out.

  • With increased scanning experience and full visualization of the appendix from base to tip, the reliability of PoCUS as a rule-out tool may improve, but this requires a high level of proficiency.

Pitfalls

The sensitivity for PoCUS in diagnosing appendicitis in pediatrics ranges from 89-96% [8,9], depending on operator experience, age, patient body habitus, and appendix position.  The most significant pitfall is that the normal appendix is far more difficult to identify than the abnormal appendix, leading to a higher rate of nondiagnostic studies. Additionally, retrocecal or pelvic positioning (Figure 15), perforation, overlying bowel gas (figure 16), and increased body habitus can obscure visualization, making diagnosis more challenging.

A common pitfall is mistaking normal small bowel for the appendix; to avoid this, confirm that the structure is blind-ended and check for peristalsis (as active movement suggests bowel rather than the appendix) and assess size and compressibility (via graded compressions), as small bowel is typically larger in diameter and more compressible than the appendix.

Other limitations include patient discomfort and pain during the examination. This can make the procedure more challenging, particularly in children with more severe symptoms, as they may struggle to remain still or tolerate the pressure applied during the examination.  To optimize imaging, consider using analgesia, ensuring parental presence, and utilizing distraction techniques to help the child remain still and tolerate the pressure applied during the examination.

Another limitation to consider is the visualization of the entire appendix. While ideally the entire appendix from the cecal junction to the tip should be visualized, this can be challenging and is not always possible in practice.

Proper image acquisition and review are essential to ensure accurate identification of the appendix, with careful correlation to clinical findings.

 

 

Figure 17:  Retrocecal position of the appendix.  The cecum is seen to screen left, and the terminal ileum, which looks like a cut tomato, is to screen right. Video courtesy of Dave Kirschner, used with permission.

 

Figure 18: Cross-section of the Appendix in the RLQ intermittently visible, obscured at times by overlying bowel gas. Appendix in and out in RLQ. Video courtesy of Dave Kirschner, used with permission.

What is NOT Normal

 

Primary Findings:

Ultrasound findings in acute appendicitis typically include [16,17]:

*Most typically a total diameter of >6mm has been used, however it is important to note that there is variability in normal appendix size and some institutions have had success with adjusted criteria to increase specificity and therefore decrease the negative laparotomy rate [18]

** In cases of acute appendicitis, the appendix typically does not compress under probe pressure [19]. However, if perforation has occurred, the appendix may appear compressible, which can complicate the assessment [20]

 

Figure 9: Inflamed appendix long axis with fluid within the lumen and surrounding hyperechoic fat. Video courtesy of Dave Kirschner, used with permission

 

Figure 10: Inflamed appendix in short axis. Image courtesy of Dave Kirschner, used with permission

 

Figure 11: Easily visualized round, thick-walled structure – Cross section of inflamed appendix. Video courtesy of Dave Kirschner, used with permission.

 

Secondary/Supportive Findings

 

Figure 12: Hyperechoic, reactive fat surrounding the inflamed appendix. Borbély Márton, CC BY-SA 4.0  via Wikimedia Commons [22]

 

Figure 13: Peri-appendiceal simple fluid collection

 

Figure 14: Inflamed appendix with color doppler displaying the “ring of fire” appearance. Image courtesy of Dave Kirschner, used with permission.

 

Figure 15: Inflamed appendix with appendicolith. Video courtesy of Dave Kirschner, used with permission.

 

Figure 16: Localized lymphadenopathy at the RLQ

What is Normal

On ultrasound, the appendix appears as a blind-ended tubular structure in the long axis and a target-like or oval structure in the short axis.

A normal appendix has the following sonographic features:
–	Thin (≤ 6mm)
–	Layered appearance (gut signature). The lumen may contain air, fluid or debris
–	Compressible with gentle probe pressure
–	Minimal vascularity
–	No peristalsis
–	Difficult to locate (due to variable tip position)

 

Figure 5  Long-axis view of the appendix tip, demonstrating a normal appearance

 

Figure 7 Normal appendix in short axis

 

Figure 8: Normal appendix in cross-section (yellow arrow) off the colon (pink arrow) medially. Video courtesy of Dave Kirschner, used with permission.

 

 

 

 

Anatomy Review: What am I looking at?

 

The appendix is a small, blind-ended tubular structure.  The appendix typically arises from the posteromedial aspect of the cecum, just below the ileocecal valve. The tip can have variable position within the right lower quadrant and is often found below or slightly posterior to the terminal ileum and anterior to the iliac vessels.

Less commonly, the appendix can be retrocecal, extending behind the cecum making visualization more difficult, or have a pelvic position, where it extends downward into the pelvis, closer to the bladder and reproductive organs. Additionally, it can sometimes extend laterally from the cecum, which may also affect its visualization.

 

 

Figure 1: Typical anatomical position of the appendix in the RLQ

 

 

Figure 2: Transverse image of the RLQ demonstrating anatomical landmarks (Iliac vessels & Psoas muscle) used to identify the appendix on PoCUS

Figure 3: TTransverse image of the RLQ anatomy, showing the cecum positioned lateral to the psoas muscle and the TI medially—key landmarks for locating the appendix on PoCUS

Figure 4: Transverse image of the RLQ showing the “typical” position of the appendix

 

Figure 5: Transverse video of the RLQ anatomy 

Stepwise Technique Overview

Patient position: Supine

 

1. Assess point of maximal tenderness

2. Identify anatomical landmarks of the RLQ

3. Attempt left posterior oblique position to troubleshoot when having difficulty identifying the appendix

4. If a structure of interest is identified:

i. Short axis sweep: slide in short axis to review entire length from base to tip

ii. Long axis rotation: Rotate to view in long axis

– Try to visualize and capture the entire length of the appendix from the cecal junction to the tip

iii. Apply color doppler

–  Select the color doppler function and set the color box over the area of interest, ensuring it is slightly larger to include surrounding tissue

–  Use a low velocity scale and adjust the color gain to enhance sensitivity to flow.

iv. Assess compressibility

– In short axis, apply compression to assess compressibility

– Be sure to document the compressibility with a video clip or a buddy view (split-screen) showing images with and without probe compression. 

v. Assess surround structures: look for secondary signs and document any findings

 

Point of maximal tenderness

This is the preferred starting point for appendicitis

1. Have the patient point with one finger to the spot that hurts the most

2. Place the probe in this spot, in the transverse position (probe marker toward patients right)

3. Review the immediate region in transverse and sagittal plane

** Tip: Identifying the point of maximal tenderness can require some coaching in smaller children

 

Anatomical Landmarks with identification of the cecum/ileocecal region

This technique used a systematic approach to identify first the anatomic landmarks in the immediate region of the appendix, then the cecum and ileocecal region. 

1. Place the probe in the transverse position in the right lower quadrant

2. Identify the iliac vessels and psoas muscle (Figure 2)

3. Look laterally (screen left) to identify the cecum (Figure 3)

4. Look for the origin of the terminal ilium posterior/medially from the cecum

–  The appendix typically arises posterior/medially from the cecum and caudal/posterior to the TI, draping anteriorly over the iliac vessels

5. Scan the area in transverse and sagittal planes until you can identify the appendix or any secondary findings

 

 

Indications

• Rule-in test for appendicitis
• Clinical suspicion for appendicitis including but not limited to:
  • Right lower quadrant pain
  • Guarding and rebound tenderness
  • Fever, nausea, vomiting
  • Anorexia
  • Migratory pain from periumbilical region
  • Positive risk calculation (Alvarado score, Pediatric Appendicitis Score, Pediatric Appendicitis Risk Calculator (pARC)) [13-15]

PoCUS is appropriate in the same clinical scenarios that radiology-based imaging would be indicated. Physicians might elect to perform POCUS when this imaging is not available or timely, or in cases where POCUS might facilitate treatment or transfer decisions and expedite care.

 

Equipment

• Ultrasound machine
• High frequency linear probe (curvilinear probe for obese or older children)
• Ultrasound gel

Introduction

Acute appendicitis is a common surgical emergency among children and adolescents, affecting tens of millions of patients globally each year, with the highest incidence occurring between ages 10 and 19 [1,2]. Prior to the advent of medical imaging and modern surgical techniques, it accounted for significant morbidity and mortality [3]. In the modern era in North America death secondary to acute appendicitis and its complications have become rare, with decreased incidence, improved diagnosis, increased treatment options, and availability of prompt surgical management all playing a role in the improvement in outcomes [4]. Diagnosis of appendicitis typically involves a combination of clinical evaluation and medical imaging, which plays a central role in confirming the diagnosis and guiding management. While history and physical examination remain important, most major centers rely on imaging before proceeding to surgery, especially in cases with equivocal presentations. Scoring systems may also be used to support decision-making and determine the need for imaging [5,6]

Why Ultrasound?

Ultrasound is a valuable diagnostic tool in cases of suspected appendicitis, particularly in children and pregnant populations, where minimizing radiation exposure is paramount. It is a non-invasive modality and does not require complete stillness, making it particularly suitable for younger children or those who may have difficulty remaining still for cross-sectional imaging such as CT or MRI.

Ultrasound has high sensitivity  in detecting inflammation and structural abnormalities in the appendix, allowing for dynamic assessment of the appendix and surrounding tissues [7]. It also offers sufficient specificity to aid in distinguishing between uncomplicated and complicated appendicitis [7]. Its diagnostic performance can vary depending on factors such as operator experience and patient characteristics, including body habitus, difficulty tolerating probe pressure, and the presence of bowel gas, among others. Despite this variability, ultrasound for the diagnosis of acute appendicitis in pediatric patients by radiology (RADUS) has demonstrated a sensitivity of 97.1% and specificity of 94.8%, and when nondiagnostic studies are excluded, these values increase to 98.8% and 98.3%, respectively [7].

 There is, however, high variability in the sensitivity and specificity reported across the publications included in all three analyses [8-10], but overall, the data supports PoCUS as a valuable tool for diagnosing acute appendicitis, particularly in pediatric patients.

Additionally, PoCUS for appendicitis allows real-time imaging, and can be readily performed at the bedside, facilitating prompt diagnosis and timely initiation of appropriate treatment, thereby reducing the risk of complications associated with appendicitis. Studies have shown that ED PoCUS can significantly reduce pediatric ED length of stay when performed by both fellowship and non-fellowship PoCUS trained emergency physicians [11,12] and reduce CT usage [11].

Considering these advantages, it is important to recognize that PoCUS for appendicitis should be viewed as a useful diagnostic tool, with its strengths in real-time imaging and immediate assessment. However, due to the prevalence of non-diagnostic exams, it is most effective when used as a rule-in test, where a positive result supports the diagnosis—helping guide immediate management decisions, but a negative scan alone does not reliably rule it out.

 

Table 1: Summary chart of Sensitivity and Specificity values for diagnosing appendicitis in pediatric populations

*CI = 95%. EP = Emergency physician