Prostate Cancer: CAT Scans

Medically Reviewed by Jennifer Robinson, MD on January 26, 2022
3 min read

A CAT scan (also called a CT scan) uses X-rays and computers to produce an image of a cross-section of the body. The cross-sectional pictures are like a slice of bread taken from a freshly sliced loaf. This image allows your doctor to check for swollen or enlarged lymph nodes, which might mean that cancer has spread.

Generally, a CAT scan is only used if the cancer is large by physical examination, looks aggressive on microscopic examination, or is associated with a very high PSA level.


If a dye (also called intravenous contrast material) is required for your CAT scan, you may be instructed to have a blood test first. The purpose of the blood test is to make sure your kidneys will be able to get rid of the dye. Not getting this blood test may delay your CAT scan appointment.

Drink only clear liquids after midnight the night before your scan. Clear liquids include things you can see through (not including alcohol). Examples include clear broth, tea, strained fruit juices, strained vegetable soup, black coffee, and ginger ale. You may also eat plain Jell-O.

Here's what you need to know for the day of the test:

  • Plan to arrive 15 minutes before your scheduled appointment time.
  • Don't eat or drink anything for 4 hours before your scan appointment.
  • If you are told to drink a special solution ("oral preparation") to prepare for your scan, you will receive the solution and instructions. Follow the instructions carefully.
  • Continue taking your medications as usual. Consult your doctor if you have questions.
  • You will be asked to change into a hospital gown because snaps and zippers in street clothes can interfere with the scan. You also may be asked to remove your watch or any jewelry.
  • Leave valuables such as jewelry or credit cards and other valuables at home.
  • Allow 1 hour for your CAT scan. Most scans take from 15 to 60 minutes.
  • After the test is done, a radiologist will review the results.


Depending on the type of scan you need, a dye may be injected into your vein so the radiologist can better see the body structures on the image.

After the dye is injected, you may feel flushed or you may have a metallic taste in your mouth. These are common reactions. If you notice shortness of breath or any unusual symptoms, tell the technician.

The technician will help you lie in the correct position on the examining table. The table will then automatically move into place for imaging. Lie as still as possible during the entire procedure. Movement could blur the images. You may be asked to hold your breath briefly while each X-ray image is taken.

Generally, you can resume your usual activities and normal meals right away. Your doctor will discuss the results with you.