May Be Caused by

 Common

Abdominal mass

Ascites

Bilateral rib fractures with guarding

Cystic abdominal mass

Dressler syndrome

Expiratory or poor inspiratory film

Hepatomegaly and splenomegaly

Obesity

Peritoneal hemorrhage

Peritoneal lavage

Peritonitis

Pneumoperitoneum

Postpericardiotomy syndrome

Pregnancy

Trauma

 Uncommon

Bilateral eventration

Bilateral lobar atelectasis

Bilateral pleural disease

Bilateral pulmonary thromboembolism with infarction

Bilateral subphrenic abscess

Laryngotracheal foreign body

Myotonic dystrophy

Neuromuscular disorder

Poliomyelitis

Systemic lupus erythematosus