Venography is used to determine whether you have a blood clot in your leg, a condition called deep vein thrombosis. This is a serious condition because if the clot breaks free, it could travel to your lungs, creating a potentially fatal condition called pulmonary embolism.
In this test, a contrast solution (or dye) is slowly injected into your leg as you lie on a tilting X-ray table. The dye causes a warm, flushed feeling in the leg and might also make you feel nauseous. X-rays are taken to identify the location of the clot. After the test, a clear fluid is injected in the same spot to clear the dye from your veins. The test takes less than an hour and can be done on an outpatient basis.
You may be asked to fast or drink only clear liquids for 4 hours before the test. Because the contrast solution contains iodine, notify your doctor if you are allergic or have had a previous bad reaction to a contrast solution. You should not have venography if you have kidney (renal) problems. After the test, you should drink plenty of fluids to flush the remaining contrast solution from your system. You may experience some soreness, but notify your doctor if there is swelling, redness, pain or fever.

This definition is in context to Orthopaedic. See more contextual defintions for Venography.