Catheters are hollow tubes, usually made of plastic or rubber, that either deliver or remove fluids to or from the body. They are one of the oldest devices in medicine, first used by the Greek physician Erastratus in the third century B.C.E. Practical applications of catheters in medicine are almost boundless, and new applications are developed frequently. Common uses of catheters are discussed below.

The foley catheter treats urinary incontinence or is used during long medical procedures and surgeries. Women who have an epidural during the labor and delivery of a child will generally have a foley catheter placed because the epidural anesthetics result in a loss of bladder control.

Intravenous (IV) therapy also relies on a catheter to, generally, transfer fluids into the body. IVs can also be used to extract fluids from the body. When donating blood, for example, an IV is used to collect blood from the body and through the catheter conduit, store it in plastic bags for later use. Completing the circle, patients needing transfusions receive the blood via catheters or caths.

Catheters are also greatly beneficial in diagnosis and treatment of various cardiac conditions. An angiogram, or catheterization, inserts a cath directly into an artery, gently working its way up to the heart. The cardiologist is able to visualize, through this procedure, the heart, blood vessels and pressure, and any blockages or anomalies. This minimally invasive procedure is often done with mild sedation as opposed to general anesthesia, and thus can be used on seriously ill patients who are at greatest risk under general anesthesia. Recovery from an angiogram is quick and it is generally considered an outpatient procedure.

Through using angiography, physicians developed a way to clear blockages or open narrow passageways in arteries (angioplasty) using a balloon catheter. When the cardiologist encounters a blockage, a small portion of the catheter is slowly inflated to clear the blockage. This particular usage of the catheter has eliminated, for many patients, the need to undergo the far more stressful and invasive coronary bypass surgery.

Catheters also prove useful in Chorionic villi sampling, where a sample taken from the embryonic membrane in the uterus provides expectant parents with information about whether their child has certain types of birth defects or chromosomal anomalies. The extraction of amniotic fluid for amniocentesis relies on the catheter, as does harvesting eggs or implanting embryos in women who cannot conceive by other means.

These examples represent just a tithe of how catheters are used. When canals were first built to open up waterways and provide new and shorter means of transportation, they were considered as one of the most important inventions to humans. The catheter is analogous to the canal, providing the medical profession with immediate access to our bodies, and some of the most efficient ways of improving the health of all people.