A number of conditions can cause an elevated hemidiaphragm. It is helpful to separate these into groups above, below and involving the diaphragm.
Above the diaphragm:
(1) atelectasis
(2) status post lobectomy or pneumonectomy
(3) pulmonary hypoplasia
Affecting the diaphragm:
(1) phrenic nerve palsy
(2) diaphragmatic eventration
(3) contralateral stroke (middle cerebral artery)
(4) diaphragmatic rupture
(5) rib fracture with splinting
(6) diaphragmatic hernia
Below the diaphragm:
(1) intra-abdominal tumor
(2) subphrenic abscess
(3) distended stomach
(4) distended colon (Chilaiditi sign, etc)
(5) pancreatitis
(6) ascites
(7) hepatomegaly
