Diagnostic prediction of complicated appendicitis by combined clinical and radiological appendicitis severity index (APSI)



To develop a routinely applicable severity index for the management of acute appendicitis in adults using combined clinical and radiological parameters and retroperitoneal space planes (RSP).


Two hundred consecutive patients with histologically proven acute appendicitis and available presurgical CT scans were analysed retrospectively. Two radiologists assessed all CT scans for morphologic sings of appendicitis and six RSP. Clinical parameters were age, body temperature, C-reactive protein (CRP), white blood cell count, and duration of symptoms. Radiological parameters were appendix diameter and wall thickness, periappendiceal fat stranding and fluid, intraluminal and extraluminal air, thinning of appendiceal wall, caecal wall thickening, appendicolith and abscess formation.


One hundred and three patients (51%) had histologically proven complicated appendicitis. Based on three clinical (age ≥52 years, body temperature ≥37.5°C, duration of symptoms ≥48 h) and four computed tomography (CT) findings (appendix diameter ≥14 mm, presence of periappendiceal fluid, extraluminal air, perityphlitic abscess), the APSI was developed using regression coefficients of multivariate logistic regression analyses with a maximum of 10 points. A score of ≥4 points predicted complicated appendicitis with a positive predictive value of 92% and a negative predictive value of 83%. Substantial to excellent interobserver agreement was found for the four radiological parameters of the APSI [intraclass correlation coefficient (ICC), 0.78-0.83]. The RSP evaluation presented no added value for the diagnosis of complicated appendicitis.


Using APSI, an accurate and simple prediction of complicated appendicitis in adults was possible. The RSP count was not useful for the diagnosis of complicated appendicitis.

Key points

• Appendicitis severity score provides an accurate and simple prediction of complicated appendicitis

• Appendicitis severity score ≥4 accurately predicted complicated appendicitis (PPV 92%;NPV 83%)

• Evaluation of retroperitoneal space planes was not useful in diagnosing complicated appendicitis

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Acute appendicitis


Appendicitis severity index


Anterior renal fascia


Bridging septa


Combined fascial plane


C-reactive protein


Estimated glomerular filtration rate


Lateroconal plane


Retrorenal plane


Retroperitoneal space planes


White blood cell


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Correspondence to Maxim Avanesov.

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The scientific guarantor of this publication is Dr. Maxim Avanesov.

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The authors of this manuscript declare no relationships with any companies, whose products or services may be related to the subject matter of the article.

Statistics and biometry

One of the authors has significant statistical expertise.

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Written informed consent was waived by the Institutional Review Board.

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Institutional Review Board approval was obtained.


• retrospective

• diagnostic study

• observational

• performed at one institution

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Avanesov, M., Wiese, N.J., Karul, M. et al. Diagnostic prediction of complicated appendicitis by combined clinical and radiological appendicitis severity index (APSI). Eur Radiol 28, 3601–3610 (2018). https://doi.org/10.1007/s00330-018-5339-9

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  • Perforated appendicitis
  • Decision support techniques
  • Appendectomy
  • Retroperitoneal space
  • Spiral computed tomography