What is one sign of stenosis in a blood vessel?

Narrowing of the lumen is a key indicator of stenosis in a blood vessel. Stenosis refers to the abnormal narrowing of a blood vessel or heart valve, which can restrict blood flow and lead to various complications. When the lumen, or the interior space of the blood vessel, becomes narrower, it can impede the normal flow of blood. This narrowing can result from various factors such as plaque buildup, inflammation, or congenital conditions.

In contrast, the other options represent different phenomena that do not align with the definition of stenosis. Increased blood flow, for example, indicates greater blood circulation, which is the opposite of what occurs in stenosis. Abnormal widening would suggest an expansion or dilation of the vessel rather than constriction, and pain during movement can be a symptom of various conditions, including ischemic pain from narrowed vessels, but it does not specifically define stenosis itself.