We present a 92-year-old elderly male experiencing acute left flank pain one day before his hospital visit. Left side pleural effusion was noted via the chest X-ray; chest computerized tomography (CT) was then performed and led to the accidental discovery of a lung abscess over the left lower lobe. Atypical symptoms in elderly patients can render accurate diagnosis difficult. It is the hope of the authors that this case report can help clinical physicians develop a stronger interest in and a closer attention to the issue concerning atypical presentations of illnesses in elderly patients.