Fig. 2.

Algorithm. *The cut-off values are based upon the study by Ebell et al. [29]. **One could consider performing additional imaging studies in patients with high probability based upon the Alvarado score in order to reduce the negative appendectomy rate. ***Ultrasound should be performed as a first level diagnostic imaging study, although in specific patient groups (such as the obese) an immediate CT scan might be considered. ****In case of an inconclusive result from the ultrasound, we recommend that additional imaging studies should be performed. Either a CT or MRI is preferred although it is recommended to perform an MRI in children and pregnant patients. It is therefore obligated to rule out pregnancy before a CT scan is obtained in a woman of reproductive age suspected of appendicitis. *****In case all the imaging studies are inconclusive, patients should be observed and reassessed. Diagnostic laparoscopy should be reserved for those patients with a continuous high index of suspicion after reassessment. ******In case of low probability based upon the Alvarado score, other diagnoses should be excluded and the patient can be either discharged with good instruction (with an optional reassessment the next day) or admitted for observation if the clinical condition mandates this. In case appendicitis is excluded, patients should be treated for the set diagnosis according to the local protocols