Acute appendicitis rarely presents in the form or urinary tract symptoms. Atypical forms of acute appendicitis occur more frequently in subjects infected by the human immunodeficiency virus (HIV). The authors report a case of acute appendicitis in an HIV-infected subject mimicking acute pyelonephritis secondary to obstruction. Atypical forms of acute appendicitis must be diagnosed and treated as early as possible. Computed tomography plays an essential role in the diagnostic assessment of abdominal and lumbar symptoms in HIV-infected patients.