Pleural effusion: This is often the most common cause of hemidiaphragmatic elevation due to the accumulation of fluid in the pleural space, which can be due to various reasons such as infection, malignancy, or heart failure. The fluid accumulation can push the diaphragm upwards, leading to its elevation.

Atelectasis: Collapse of the lung tissue can cause the diaphragm to appear elevated on imaging due to the reduced lung volume. This can be due to obstruction of the airways or other factors leading to lung volume loss.
Pneumonia: Inflammation of the lung tissue, especially if localized to the lower lobe, can cause elevation of the hemidiaphragm due to consolidation and volume loss.
Diaphragmatic eventration: A condition where there is an abnormal elevation of part or all of the diaphragm due to thinning or weakness, which can be congenital or acquired.

Pulmonary embolism: Although less common as a direct cause of hemidiaphragmatic elevation, a large pulmonary embolism can lead to infarction and atelectasis, indirectly causing elevation. Missing this diagnosis can be fatal.
Diaphragmatic rupture: A traumatic injury to the diaphragm can lead to herniation of abdominal contents into the thoracic cavity, which is a surgical emergency.
Malignancy: Tumors affecting the diaphragm, lung, or pleura can cause elevation due to mass effect or secondary complications like effusion or atelectasis. Early detection is crucial for management.

Diaphragmatic paralysis: Weakness or paralysis of the diaphragm due to neurological conditions or trauma can lead to elevation, especially if unilateral.
Subphrenic abscess: An abscess located below the diaphragm can push it upwards, although this is less common with modern antibiotic treatments.
Hepatomegaly or liver mass: Enlargement of the liver or a liver mass can push the right hemidiaphragm upwards, although this would typically be associated with other clinical findings.