Are Cases of Nonvisualized Appendix on Ultrasound Not Actually Appendicitis? Single-Center Results

Background: Ultrasonography (USG), which is used as the first step in the diagnosis of acute appendicitis (AA), sometimes cannot visualize the appendix. The aim of this study was to retrospectively analyze the clinical, imaging, and pathology results of these cases and to provide information to clinicians about the next step to be taken.

Methods: The study was performed retrospectively between January 1, 2021 and December 31, 2021. Patients with a prediagnosis of AA who underwent USG as the first-line imaging modality and in whom the appendix could not be visualized were included. Imaging, clinical, and pathology results of the patients were analyzed, and the study was completed by comparing patients with and without computed tomography (CT) scans as well as patients with and without AA diagnosis.

Results: The study included 176 patients aged 18-89 years, 63 (35.8%) of whom were male and 113 (64.2%) female. The mean age was 37.5 ± 17.8 years. CT was not performed in 97 patients (55.1%), while it was performed in 79 patients (44.9%). Of the patients, 121 (68.7%) were discharged and 55 (31.2%) were hospitalized. Of the patients who were hospitalized, 36 (20.5%) received medical treatment and 19 (10.7%) received surgical treatment. Fifteen patients (8.5%) were pathologically diagnosed with AA. Two patients (1.1%) who were discharged without CT were subsequently diagnosed with AA. The white blood cell (WBC) count of patients operated on for AA was 13.4 ± 3.9 × 10³/mL, while the WBC count of the other patients was 10.3 ± 4.2 × 10³/mL (p = 0.009). The proportion of patients with an Alvarado score of ≥ 6 was 80% in patients diagnosed with AA, while this rate was 4.3% in other patients (p < 0.001).

Conclusions: In cases of a nonvisualized appendix on USG, the absence of leukocytosis and an Alvarado score below 6 may suggest a reduced likelihood of AA. Consequently, further investigations, such as CT and magnetic resonance imaging, could be avoided.