Which of the following statements about pyogenic abscess of the liver are true?

Involvement of the right lobe with abscess formation approximates 70% of pyogenic abscesses. This is thought to be due to the streaming effect of superior mesenteric venous inflow to the right lobe. In addition, the greater volume of the right lobe predisposes more tissue to seeding by bacterial organisms. While appendicitis comprised 25% to 40% of cases in early series, early recognition and operative therapy for appendicitis have reduced its impoance significantly. In current series, malignant or benign biliary obstruction is the underlying cause of 35% to 50% of cases. Recent studies have shown that the underlying disease or an immunocompromised host is more impoant prognostically than solitary versus multiple abscesses.