Alternative diagnoses of acute appendicitis on helical CT with intravenous and rectal contrast

At our institution, helical CT of the abdomen and pelvis with intravenous and rectal contrast (CTRC) has become the modality of choice for investigation of patients with right lower quadrant pain and clinical suspicion of acute appendicitis. CTRC has proven useful for the diagnosis of acute appendicitis (AA) and at the same time identifies alternative diagnoses mimicking AA. This pictorial assay illustrates the imaging findings of AA and its mimickers including primary epiploic appendagitis, right-sided diverticulitis, torsion of Meckel's diverticulum, gynecologic disorders, obstructive uropathy, right lower lobe pneumonia, and other conditions.