Non-Visualization of the Appendix Without Inflammatory Features on MRI Excludes Acute Appendicitis in Children and...

This is a single-center retrospective study to determine whether the absence of inflammatory features in the right lower quadrant excludes appendicitis in children and young adults in the context of a non-visualized appendix on MRI.

IRB approved retrospective review of MRI appendicitis exams performed at our institution from July 2024 to July 2025. Variables collected included: a) patient demographics; b) MRI findings including the visualization of the appendix and presence of appendicitis; c) follow-up imaging within 7 days (CT, MRI, US); d) diagnosis on follow-up imaging; e) surgical diagnosis and pathology findings. Categorical variables were summarized using counts and percentages. Diagnostic performance was assessed using the Negative Predictive Value (NPV).

A total of 1025 MRI examinations were reviewed. The appendix was not visualized in 265 (25.5%), 257/265 (97.0%) of which had no inflammatory features. Two (0.8%) cases were reported as perforated appendicitis without visible appendix. Six (2.3%) cases had inflammation present: four attributed to an alternate cause and two reported as possible appendicitis. Of the 257 cases with non-visualization of the appendix and no inflammatory findings, 253 patients had no surgery. The remaining 4 had surgical intervention for unrelated findings: two for ovarian torsion, one for intrauterine device expulsion and one for cholelithiasis. No patient was found to have appendicitis, equating to a NPV of 100% (257/257).

MRI with non-visualization of the appendix and absence of inflammatory findings can safely be managed as negative for acute appendicitis, with appropriate clinical follow-up.