There is no consensus on the best diagnostic pathway for suspected appendicitis. Some people seem to refer every patient with right iliac fossa (RIF) pain to the surgeons; others require guarding and a fever. Many trust in their clinical examination (guarding, rebound, percussion tenderness, and Rovsing's, psoas or obturator signs), but studies have shown all these clinical signs to be weak discriminators individually, unless perforation has occurred.?[1]?
So what?
In general, the problem with suspected appendicitis is not underdiagnosis but overtreatment. It has been known for some time that more normal appendices are removed in the UK than most other high-income countries. This is likely due, at least in part, to reduced rates of imaging. A stark illustration of this discrepancy is provided by a 2016 study?[2]? which compared common practice in the UK vs the Netherlands. Preoperative imaging was obtained in 32.8% of UK cases vs 99.5% of Netherlands cases. Normal appendicectomy rates (NAR) were 20.6% (UK) vs 3.2% (Netherlands).
Another reason for the UK's high NAR could be the low utilization of risk scoring tools. A recent international consensus document published by the European Association of Endoscopic Surgery?[3]? recommended routine clinical risk stratification for all cases of suspected appendicitis (they suggested the Alvarado score). Low risk patients should be discharged with safety netting, high risk patients should be worked up for surgery, and intermediate risk patients should have imaging, usually in the form of ultrasound.
Scoring systems are not currently recommended in the UK, due to lack of familiarity.?[4]? The NICE Clinical Knowledge Summary is also curiously silent on the use of imaging for suspected appendicitis.
The paper Nepogodiev D, Matthews JH, Morley GL. Evaluation of appendicitis risk prediction models in adults with suspected appendicitis. Br J Surg. 2020;107(1):73-86?[5]?
This was a prospective cohort study involving 5,345 patients across 154 UK hospitals - the RIFT study. It's actually the largest ever study of RIF pain in the world! The focus of this paper, the first of several planned data analyses, was to find the best risk stratification model for identifying low risk patients.
Inclusion: patients aged 16-45 who were referred by GP or Emergency Medicine to the on-call surgical team with suspected appendicitis
Exclusion: pregnant, prior appendicectomy(!), appendicectomy performed but no histology available
The study authors spent some time researching all the risk prediction models in the literature, and then used each on the cases from their study to see which performed the best.
Results from the data collection
Overall, the rate of normal appendicectomy (NAR) was 20%
Likelihood of surgery in women: 32%NAR rate in women: 28%Rate of confirmed appendicitis in women: 17%
Likelihood of surgery in men: 60%NAR rate in men: 12%Rate of confirmed appendicitis in men: 49%
Performance of risk models
In women, the Adult Appendicitis Score (AAS) performed best. Using a cut-off score of 8 or less, the AAS would have correctly assigned 63.1% of patients without appendicitis into the low risk group. Out of all those in the low risk group, only 3.7% would have been false negatives (i.e. actually had appendicitis)
In men, the Appendicitis Inflammatory Response Score (AIRS) was best. Using a cut-off score of 2 or less would have placed 24.7% of those without appendicitis in the low risk group. The false negative rate would have been 2.4%.
The bottom line
The UK has one of the highest rates of normal appendicectomy in the world, and this is particularly high in women (28%).
Using the Adult Appendicitis Score (AAS) would reveal many cases to be low risk for appendicitis, thus saving these patients from further workup, referral, imaging and potentially unnecessary surgery.
What is the Adult Appendicitis Score?
Well, it's a combination of the following rather obvious indicators of appendicitis. Collating them together is more sensitive than taking each in isolation...
Gender
Time from symptom onset
RIF pain
Pain migrated from central abdomen
RIF tenderness on examination
Guarding
White cell count
Neutrophil count
CRP level
AAS is available hereAIRS is available hereA combination tool has been developed by the authors of the study and is available here
Andersson R. Meta-analysis of the clinical and laboratory diagnosis of appendicitis. Br J Surg [Internet] 2004;91(1):28–37. Available from: https://www.ncbi.nlm.nih.gov/pubmed/14716790
van R, Bolmers M, Schreinemacher M, Bemelman W, van G, Pinkney T, et al. Diagnosing acute appendicitis: surgery or imaging? Colorectal Dis [Internet] 2016;18(12):1129–32. Available from: https://www.ncbi.nlm.nih.gov/pubmed/27454191
Gorter R, Eker H, Gorter-Stam M, Abis G, Acharya A, Ankersmit M, et al. Diagnosis and management of acute appendicitis. EAES consensus development conference 2015. Surg Endosc [Internet] 2016;30(11):4668–90. Available from: https://www.ncbi.nlm.nih.gov/pubmed/27660247
NICE (National Institute for Health and Care Excellence). Appendicitis [Internet]. NICE Clinical Knowledge Summaries2015 [cited 2020 Feb];Available from: https://cks.nice.org.uk/appendicitis#!topicSummary 5. Bhangu A, RIFT Study Group on behalf of the West Midlands Research Collaborative. Evaluation of appendicitis risk prediction models in adults with suspected appendicitis. Br J Surg [Internet] 2020;107(1):73–86. Available from: https://www.ncbi.nlm.nih.gov/pubmed/31797357
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