Which condition involves inflammation of a vein?

Phlebitis is the condition characterized specifically by inflammation of a vein. This inflammation can occur due to various factors, such as trauma to the vein, infection, or irritation from intravenous catheter placement or the infusion of certain medications. The symptoms of phlebitis may include redness, swelling, warmth, and pain along the affected vein.

Infiltration refers to the leakage of intravenous fluid into the surrounding tissue, which can cause swelling and discomfort but does not pertain to inflammation of the vein itself. Extravasation involves the escape of intravenous drugs or fluids into the surrounding tissue, often leading to more significant injury than infiltration, particularly with vesicant medications, but it too does not specifically denote inflammation of a vein. Fluid overload is a condition that occurs when excessive fluid is administered into the bloodstream, leading to complications such as edema and cardiovascular strain, but it does not relate to vein inflammation. Thus, phlebitis distinctly connects to the inflammation of a vein, making it the correct choice.