Do I have to get a CT scan previous to removing my varicose veins? My Dr suggested yes.

An ultrasound is typically all that is needed and is the standard of care for diagnosing venous problems.  If there are abnormal findings on ultrasound or physical exam to suggest venous pathology in the pelvis or abdomen then a CT venogram could help determine the anatomy and level of pathology.  An MRI would be an alternative that does not involve radiation and intravenous ultrasound can also be done but is more invasive and is typically done concurrently with intention to treat such as in placing venous stents for iliac vein compression.  

Most patients with varicose veins can be adequately evaluated using venous duplex ultrasound from the level of the groin crease and below. There are circumstances where a CT scan or MRV might be needed and valuable before proceeding with treatment. If your examination or history suggests a problem above the groin crease then these tests may be necessary. If you have a prior history of blood clots or varicose veins involving the labia, lower abdomen, or buttocks then a CT scan/MRV may be important to determine if there is a blockage or venous insufficiency in the veins of the pelvis or abdomen. An ultrasound is more than adequate in the case of routine varicose veins.