Ultrasound vs. Reality: A Multi-centre Study of Real-World Imaging Practices in Suspected Appendicitis in the United Kingdom

Abstract

Background: Appendicitis is one of the leading causes for emergency surgery in the United Kingdom (UK), with approximately 50,000 appendectomies performed annually. While imaging plays an increasingly important role in diagnosis, the lack of specific, unified guidelines guiding the utilisation of various imaging modalities causes ambiguity in how and when various modalities should be used.

Objective: This study aimed to evaluate how various imaging modalities are being used in day-to-day practice, the practical aspects, the challenges, and the benefits of one scan over the others. This was done by comparing the diagnostic accuracy of various scans, such as ultrasound (US), CT, and MRI scans in suspected appendicitis cases.

Methods: We retrospectively reviewed 200 recent appendectomy cases across two major hospitals in Manchester. After excluding 70 patients who either had no preoperative imaging or were diagnosed with something other than appendicitis, we analysed the radiology and histopathology reports of the remaining 130 patients. Special attention was given to the subgroup of 52 patients who initially underwent US.

Results: US had a sensitivity (Sn) of 56.25%, with 21 missed diagnoses later confirmed via CT, MRI, or histopathology. US should be commonly used for those under 18, but surprisingly, approximately two-thirds of US cases were adults, representing an inclination to use US as an initial investigation. In the under-18 group, US Sn was 80%, dropping to just 37.5% in the 18-29-year age group. US was not able to visualise the appendix in 34% (n=18) of patients, missing out on many appendicitis diagnoses. The CT scan was the most utilised scan and had a sensitivity of nearly 99%. The MRI scan, although limited in numbers, had a sensitivity of 100%.

Conclusion: While US offers benefits such as speed and no radiation exposure, its diagnostic reliability varies with the patient's body habitus and the operator's skills. The appendix was not identified in a good proportion of patients; however, when the appendix was clearly visualised, it was associated with a better sensitivity. The CT scan was the most utilised scan. It also proved to have excellent sensitivity and is quicker to perform compared to an MRI scan. The MRI scan provides CT equivalent sensitivity but without exposure to harmful radiation. However, it was being underutilised due to limitations in practicality and availability. We routinely request these scans to support the diagnosis of appendicitis, but it is important to understand their diagnostic value, limitations, and when they are most appropriately used.

Keywords: appendectomy; appendicitis; appendicitis diagnostic accuracy; diagnostic approach of appendicitis; imaging in appendicitis cases; imaging of appendix; imaging preference in appendicitis; ultrasound efficacy; ultrasound efficacy in appendicitis.

Figure 1. Flowchart presentation of the inclusion and exclusion criteria.

CT: computed tomography; MRI: magnetic resonance imaging; US: ultrasound; NAR: negative appendectomy rate Image Credit: The figure is original and derived from the data collected in the present study.

Figure 2. CT scan of a 25-year-old female from the study showing classic signs of acute appendicitis.

Typical CT findings in appendicitis include a distended, thick-walled appendix with surrounding fat stranding indicating peri-appendiceal inflammation. A) Axial cross-sectional view showing the inflamed appendix with fat stranding (arrow). B) Coronal view confirming the same finding (arrow). Image Credit: The figure is original and derived from the data collected in the present study.

Figure 3. MRI scan of a 23-year-old man from the study showing typical signs of acute appendicitis.

A) Axial T2-weighted image showing a distended, thick-walled appendix (arrow), with a surrounding hyperintense area consistent with periappendiceal edema. A small hypointense focus within the lumen suggests an appendicolith (dotted arrow). B) Coronal STIR sequence displaying the appendix (arrow) with similar finding. Image Credit: The figure is original and derived from the data collected in the present study.

Figure 4. Ultrasound scan of a 12-year-old female from the study, where the right lower abdomen shows a blind-ending tubular structure measuring 6.5 mm, consistent with a dilated appendix.

Typical ultrasonographic findings of appendicitis include a diameter ≥6 mm, wall thickening, absent peristalsis, and periappendiceal fat changes. Image Credit: The figure is original and derived from the data collected in the present study.

Figure 5. Appendicitis workup flowchart representing the flow of the appendicitis work-up observed in this study.

CT: computed tomography; MR: magnetic resonance scan; US: ultrasound scan Image Credit: The figure is original and derived from the data collected in the present study.