Elevated hemidiaphragm: Elevation of half of the diaphragm, the muscle that separates the chest cavity from the abdomen and that serves as the main muscle of respiration. The elevation of a hemidiaphragm is a significant sign of a problem.

That problem may lie below, within or above the diaphragm:

• Below the diaphragm -- In the abdomen there may be a cyst, an infection or abscess (filled with pus), hematoma (collection of blood), a tumor, or abdominal surgery.
  
• In the diaphragm -- The hemidiaphragm may be paralyzed or lax because of damage to the phrenic nerve (that controls the diaphragm) or infiltration of the diaphragm by lung cancer or another tumor.
• Above the chest -- In the chest there may be atelectasis (lung collapse), lung fibrosis, painful pleurisy, pulmonary embolus, or a rib fracture.

An elevated hemidiaphragm may be suspected on the physical examination and confirmed on an X-ray or CT of the chest or upper abdomen. It is also called a raised hemidiaphragm.