Dilation

Dilation (also dilated) is a medical term that describes the enlargement of a circular body part such as the pupil, a sphincter, or a duct. Dilation can be a normal phenomenon (such as the dilation of the pupil in low light conditions) or an abnormal phenomenon particular to a disease (such as the dilation of the bile duct when it passes a gallstone.
In some cases, dilation (or non-dilation) in an abnormal condition can indicate an underlying condition. For example, the pupils of a person suffering a drug overdose will be dilated even in response to bright light.
Category:Medical terminology