You may be offered medicine to help you relax before the test.
You sit in a special chair or on an x-ray table. The health care provider cleans your feet, and then injects a small amount of blue dye into the area (called webbing) between your toes.
Thin, bluish lines appear on the top of the foot within 15 minutes. These lines identify the lymph channels. The health care provider numbs the area, makes a small surgical cut near one of the larger blue lines, and inserts a thin flexible tube into a lymph channel. This is done on each foot. Dye (contrast medium) flows through the tube very slowly, over a period of 60 to 90 minutes.
Another method may also be used. Instead of injecting blue dye between your toes, your doctor may numb the skin over your groin and then insert a thin needle under ultrasound guidance into a lymph node in your groin. Contrast will be injected through the needle and into the lymph node using an type of pump called an insufflator.
A type of x-ray machine, called a fluoroscope, projects the images on a TV monitor. The health care provider uses the images to follow the dye as it spreads through the lymphatic system up your legs, groin, and along the back of the abdominal cavity.
Once the dye is completely injected, the catheter is removed and stitches are used to close the surgical cut. The area is bandaged. X-rays are taken of the legs, pelvis, abdomen, and chest areas. More x-rays may be taken the next day.
If the test is being done to see if breast cancer or melanoma has spread, the blue dye is mixed with a radioactive compound. Images are taken to watch how the substance spreads to other lymph nodes. This can help your doctor better understand where the cancer has spread when a biopsy is being performed.