The Optimization of a Low-dose Computed Tomography Protocol in Patients With Suspected Uncomplicated Acute Appendicitis (OPTICAP)

Acute appendicitis is one of the most common causes of abdominal pain in emergency departments as well as one of the most common indications for emergency abdominal surgery. The clinical diagnosis has been based on patient history, physical examination and laboratory findings as well as the "clinical eye" of the surgeon. Still the diagnosis remains challenging. One of the main problems is that many other disorders can mimic the clinical presentation of appendicitis, thus increasing the role of imaging techniques to aid in diagnostic accuracy. Now preoperative imaging in patients with suspected acute appendicitis is currently widely accepted as the standard of practice, and CT has been shown to clearly outperform US in terms of diagnostic performance. Nowadays, CT imaging is considered the primary imaging modality in the diagnosis for acute appendicitis as it is appraised for its high sensitivity and specificity. The main disadvantage of CT imaging is exposure to radiation. Thus the favorable diagnostic performance of CT imaging has encouraged optimization of protocols to minimize exposure to radiation through the development of low-dose CT protocols. Initial studies have indicated that contrast enhanced low-dose CT was not inferior to standard-dose contrast enhanced CT with no statistical significance in negative appendectomy rates, appendiceal perforation rates or patients requiring additional imaging.

This study focuses on the use of contrast enhanced low-dose CT imaging as a modality to differentiate between uncomplicated and complicated acute appendicitis. Differentiation between the two forms of acute appendicitis is important because according to recent studies their treatment differs. Complicated forms are still treated operatively, while uncomplicated forms can be treated conservatively with antibiotics. In the initial phase of the study, several optimized CT protocols will be created with a phantom model. The two best performing models will be selected for the second phase of the study, in which patients presenting with suspected acute appendicitis will be imaged with the two protocols. All patients participating in the study will be treated operatively, primarily with a laparoscopic appendectomy. Thus histological confirmation for the diagnosis can be achieved and compared with the CT images. The goal of this study is to optimize a well-performing low-dose CT imaging protocol to use in the diagnosis of uncomplicated acute appendicitis.