Abdominal CT scan (without contrast)

What it is

A CT scanner rotates an X-ray beam around the body and builds cross-sections from what gets through. Dense things appear bright and fatty or fluid-filled things appear dark, and that difference alone is enough to answer some questions. A stone in the kidney or ureter is chalk-bright against everything around it, and no injected dye is needed to find one — dye can actually make a stone harder to pick out, because the dye itself turns bright as the kidneys excrete it. The same logic applies to fresh bleeding and to some calcium deposits. Where a plain scan falls short is soft tissue that is all much the same density: organ tumors, abscess walls, and inflamed bowel are far easier to see once dye is in the bloodstream, which is why a with-contrast study is a separate and different order.

Why it is done

• To look for a kidney or ureter stone in someone with sudden flank pain
• To scan someone whose kidney function or contrast allergy makes injected dye a poor choice
• To follow a finding that was already visible without dye, such as a known stone or a calcification
• To look at the bones and the general outline of the organs when the clinical question does not depend on soft-tissue detail

What to expect

Preparation is minimal compared with a contrast study — there is usually no intravenous line and often no fasting, though instructions vary by facility. Metal objects and clothing with zippers or snaps come off, and patients change into a gown. The scan itself is over in a few minutes; the table slides through the ring, and the patient is asked to hold still and sometimes to hold a breath. Nothing about it hurts and there is no recovery time. Anyone who is or might be pregnant should say so before the scan. A radiologist interprets the images and sends a report to the ordering doctor.

Questions worth asking

• Which of the three abdominal CT variants was ordered — without contrast, with contrast, or both? They are three different codes at three different prices, and any price quote applies to only one of them.
• If the radiologist decides mid-exam that dye is needed after all, which code gets billed, and will I be told before the scan continues?
• Was this ordered through the emergency department? The same scan billed under an ER visit generally carries a facility charge that a scheduled outpatient appointment does not.
• If a recent CT was done elsewhere, can those images be obtained and compared instead of repeating the scan?