Why would an appendix not be mentioned in an abdominal-pelvis computed tomography (CT) scan report?

From the Guidelines

An appendix may not be mentioned in an abdominal-pelvis CT scan report because it appears normal and unremarkable, and the radiologist focuses on reporting only abnormal or clinically significant findings. According to the most recent study by Kambadakone et al 1, CT of the abdomen and pelvis is an excellent diagnostic imaging modality for the evaluation of patients with nonspecific right lower quadrant pain, and it has a high diagnostic yield for detection of appendicitis. The study reported a summary sensitivity of 95% and summary specificity of 94% for CT in the diagnosis of appendicitis.

Some possible reasons for the appendix not being mentioned in the report include:

• The appendix is difficult to visualize due to its small size, location, or surrounding structures obscuring the view
• The appendix is absent due to previous surgical removal (appendectomy)
• Technical factors such as inadequate bowel preparation, motion artifacts, or suboptimal scanning parameters limit visualization
• The radiologist prioritizes reporting more urgent or clinically relevant findings, especially in emergency situations

It's essential to note that radiologists typically follow the principle of reporting significant findings rather than describing every normal structure, and if the appendix is not specifically mentioned, it generally implies that no concerning abnormalities were identified in that organ, as supported by the study by Wang et al 1. Additionally, a study by Pooler et al 1 reported that in patients undergoing contrast-enhanced CT with oral contrast for right lower quadrant pain with diagnosis other than appendicitis at CT, the CT diagnosis was concordant with clinical diagnosis in 94.3% of cases.

In line with the latest clinical practice guideline update by the Infectious Diseases Society of America 1, CT is recommended as the initial imaging modality to diagnose acute appendicitis, with a conditional recommendation and very low certainty of evidence. The guideline also suggests that intravenous contrast is usually appropriate whenever a CT is obtained in adults with suspected acute appendicitis, but CT without intravenous contrast also has high diagnostic accuracy in detecting acute appendicitis.

Overall, the absence of mention of the appendix in an abdominal-pelvis CT scan report does not necessarily indicate a problem, and it is essential to consider the clinical context and other findings reported in the scan.

From the Research

Reasons for Non-Mention of Appendix in Abdominal-Pelvis CT Scan

• The appendix may not be visualized on a CT scan due to various factors, such as a low cecum level, minimal pericecal fat, presence of pericecal fluid, and non-identification of the ileocecal valve 2.
• In the absence of secondary inflammatory changes, the incidence of acute appendicitis is low, even if the appendix is not visualized on the CT scan 3.
• The presence of multiple secondary inflammatory changes, such as free fluid, phlegmon, and pericecal inflammatory fat changes, can provide increasing support for a diagnosis of acute appendicitis, even if the appendix is not visualized 4.

Diagnostic Accuracy of Imaging Modalities

• Ultrasound (US) is the basic diagnostic method for suspected appendicitis, while CT is necessary in patients with atypical presentation of appendicitis 5.
• Second-line US, CT, and MRI have comparable and high accuracy in helping to diagnose appendicitis in children and adults, including pregnant women 6.
• The pooled sensitivities and specificities of second-line CT for diagnosis of appendicitis in children were 96.2% and 94.6%, respectively, and in adults, the pooled sensitivities and specificities were 89.9% and 93.6%, respectively 6.

Clinical Implications

• The non-visualization of the appendix on a CT scan does not necessarily rule out acute appendicitis, and clinical correlation and further evaluation may be necessary 3, 4.
• The use of multiple imaging modalities, including US, CT, and MRI, can help improve the diagnostic accuracy of appendicitis and guide clinical management 5, 6.