Accuracy of imaging in discriminating complicated from uncomplicated appendicitis in daily clinical practice
Authors: Bolmers Matthijs D. M. , Bom Wouter J. , Scheijmans Jochem C. G. , van Geloven Anna A. W. , Boermeester Marja. A. , Bemelman Willem A. , van Rossem Charles. C. ,   on behalf of the SNAPSHOT collaborators, Van Acker GJ , Akkermans B , Akkersdijk GJ , Algie GD , Allema JH , Andeweg CS , Appeldoorn N , van Baal JG , den Bakker CM , Bartels SA , van den Berg C , Boekestijn B , den Boer FC , Boerma D , van den Boom AL , Boute MC , Bouwense SA , Bransen J , van Brussel FA , Busch OR , de Castro SM , Cense HA , Croese C , van Dalen T , Dawson I , van Dessel E , Dettmers R , Dhar N , Dohmen FY , van Dongen KW , van Duijvendijk P , Dulfer RR , Dwars BJ , Eerenberg JP , van der Elst M , van den Ende E , Fassaert LM , Fikkers JT , Foppen JW , Furnee EJ , Garssen FP , Gerhards MF , van Goor H , Gorter RR , de Graaf JS , Graat LJ , Groot J , van der Ham AC , Hamming JF , Hamminga JT , van der Harst E , Heemskerk J , Heijne A , Heikens JT , Heineman E , Hertogs R , van Heurn E , van den Hil LC , Hooftwijk AG , Hulsker CC , Hunen DR , Ibelings MS , Klaase JM , Klicks R , Knaapen L , Kortekaas RT , Kruyt F , Kwant S , Lases SS , Lettinga T , Loupatty A , Matthijsen RA , Minnee RC , Mirck B , Mitalas L , Moes D , Moorman AM , Nieuwenhuijs VB , Nieuwenhuizen GA , Nijk PD , Omloo JM , Ottenhof AG , Palamba HW , van der Peet DL , Pereboom IT , Plaisier PW , van der Ploeg AP , Raber MH , Reijen MM , Rijna H , Rosman C , Roumen RM , Scmitz RF , van der Velden APS , Scheurs WH , Sigterman TA , Smeets HJ , Sonnevled DJ , Sosef MN , Spoor SF , Stassen LP , van Steensel L , Stortelder E , Straatman J , van Susante HJ , de Hoog DES , van Scheltinga CT , Toorenvliet BR , Verbeek PC , Verseveld M , Volders JH , Vriens MR , Vriens PW , Vrouenraets BC , van de Wall BJ , Wegdam JA , Westerduin E , Wever JJ , Wijfels NA , Wijnhoven BP , Winkel TA , van der Zee DC , Zeillemaker AM , Zietse C 
Published: May 2022

Abstract
Background
Radiologic imaging can accurately diagnose acute appendicitis, but little is known about its discriminatory capacity between complicated and uncomplicated appendicitis.

Objective
This study aims to investigate the accuracy of imaging in discriminating complicated from uncomplicated appendicitis.

Methods
Data was used from the prospective, nationwide, observational SNAPSHOT appendicitis database, including patients with suspected acute appendicitis who were planned for an appendectomy. Usage of ultrasound (US), CT, MRI or a combination was recorded. Radiological reports were used to group for complicated or uncomplicated appendicitis. The reference standard was based on operative and pathological findings. Primary outcomes were sensitivity and specificity in discriminating complicated from uncomplicated appendicitis. Secondary outcomes were diagnostic accuracy results per imaging modality and for the subgroups age, BMI, and sex.

Results
Preoperative imaging was performed in 1964 patients. In 1434 patients (73%), only US was used; in 109 (6%) patients, only CT was used; and 421 (21%) patients underwent US followed by CT or MRI. Overall, imaging workup as practiced, following the national guideline, had a poor sensitivity for complicated appendicitis of only 35%, although specificity was as high as 93%. For US, accuracy for complicated appendicitis was higher in children than in adults; sensitivity 41.2% vs. 26.4% and specificity 94.6% vs. 93.4%, respectively, p = 0.003. For relevant subgroups such as age, sex and BMI, no other differences in the discriminatory performance were found.

Conclusion
A diagnostic workup with stepwise imaging, using a conditional CT or MRI strategy, poorly discriminates between complicated and uncomplicated appendicitis in daily practice.