Emergency physicians frequently encounter patients with acute urinary retention. Although most common among the elderly, pediatric and young adult patients occasionally may present with this complaint. The differential diagnosis and emergency department work-up must be age specific. We discuss the case of a young man who presented with acute urinary retention, subsequently found to be caused by undiagnosed appendicitis with appendiceal abscess formation. Only nine such cases have been reported in the literature thus far, with only one occurring in the nonpediatric population. This case represents the second such case to be reported. The importance of a thorough history, physical examination, and diagnostic work-up of patients who present with acute urinary retention, particularly those in the younger age group, is emphasized.