Patient Blog

Abdominal CT Scan with Contrast: What It Is and How It Works

abdominal CT scan with contrast male patient drinking contrast solution before CT scan

Learn what an abdominal CT scan with contrast is, when and why one is needed and how to access and understand your results—fast.

A computed tomography (CT) scan is a common imaging technique that takes X-rays from many different angles, which are then combined digitally to create a highly detailed 3D image. Formerly known as CAT scans, CT scans are essential diagnostic tools because they provide an accurate view with which doctors can identify and assess internal conditions and injuries.

Some CT scans of the abdominal area and organs require the use of a contrast agent, a liquid composed of iodine that works by making the differences between internal structures appear more defined. If you’re sent for an abdominal CT scan with contrast, this article will help you understand:

  • How an abdominal CT scan with contrast works
  • What an abdominal CT scan will show and why it may be recommended
  • How to prepare for your abdominal CT scan with contrast
  • What to do after your appointment
  • How to access and understand your abdominal CT scan results

How does an abdominal CT scan work?

During a CT scan, you lie on a table that is passed through a donut-like array of X-ray equipment. This array is a CT scanner, which rotates around you to take a series of X-ray images, creating a 2D cross-sectional “slice” at one location within the body. These slices are collected at multiple contiguous locations and then digitally compiled into a detailed 3D image.

X-rays use low-dose ionizing radiation to capture images. As the X-ray beam radiates through your internal structures, it is absorbed by degrees depending on the density of the tissues it meets. Then it is captured digitally on the other side.

The CT machine rotates to take images at 1 angle and then reconstructs them along 3 different angles to provide the radiologist with a 360° view of your body’s internal structures and organs:

  1. Coronal: the frontal view, which presents images from the front to the back of your body.
  2. Sagittal: a side view, which provides lateral images from the left to the right sides of the body.
  3. Axial: also called the transverse view, this horizontal view creates images from the top to the bottom of your body.

By combining these multiple X-ray slices, a CT scan generates more detailed images than a simple X-ray. Although they require minimal radiation exposure, a CT scan is considered a non-invasive and low-risk imaging technique.

What is contrast and why is it used?

A contrast agent is a liquid substance (usually iodine) that works by making structures with contrast presenting as white. This helps abnormalities appear more obvious, either because they become denser with contrast (enhancing/hyper-enhancing) or because the surrounding tissue becomes brighter, outlining the abnormality (hypodense).

The contrast agent is often described by the method by which it is administered:

  • An intravenous (IV) contrast agent is injected into your body to highlight areas of increased blood flow, like blood vessels or organs (e.g. liver, kidneys or spleen.
  • An oral contrast agent is swallowed and helps CT scans better identify areas of the esophagus, stomach and intestines.
  • A rectal contrast agent is inserted in the rectum to improve CT images in the large intestines and pelvic organs.

What does an abdominal CT scan show?

An abdominal CT scan can provide detailed images of all body parts and tissues found in the abdominal cavity, including:

  • Blood vessels
  • Digestive tract
  • Kidneys and other internal organs
  • Reproductive systems

Why would a doctor order a CT scan of the abdomen or pelvis with contrast?

A CT scan is generally ordered if a doctor needs an image of the inner workings of your body to locate, diagnose or monitor a specific part of your abdomen for illness or injury, such as:

  • Blood vessel clots or diseases
  • Bladder or kidney stones
  • Bone or joint fractures or breaks
  • Brain injuries or bleeds
  • Cancer
  • Digestive tract injury or illness
  • Inflammatory diseases

CT scans are usually the first choice for doctors needing detailed internal images because they are less expensive than MRIs. CT scan machines are also more widely available than MRI machines and, depending on your location, may have shorter wait times for scans.

What cannot be seen on an abdominal CT scan?

CT scans excel at creating images of hard structures like bones. They are not quite as effective as MRIs when it comes to creating detailed images of soft tissues, making it more difficult to diagnose certain types of soft-tissue diseases like endometriosis or prostate, uterine and some liver cancers.

Depending on your particular circumstances, you might be sent for a CT scan to rule out certain conditions or concerns before moving on to an MRI.

How to prepare for an abdominal CT scan appointment

Here’s a list of steps to help you prepare for your abdominal CT scan with contrast:

  • Bring your requisition with you to the imaging center. It contains valuable information and will speed up the check-in process.
  • Dress comfortably, as you’ll change into a hospital gown for your scan.
  • Remove any jewelry or other metallic objects, including metal prosthetics.
  • Fast as directed by your doctor or the imaging clinic. Traditionally, a 4-6 hour fast has been recommended for abdominal scans with contrast. You may usually drink clear liquids up to 2 hours before your CT scan.
  • Avoid caffeine for 24 hours before your scan.
  • Get bloodwork done, if required. You may need bloodwork to confirm your kidneys will process the contrast agent. Have that bloodwork completed before your appointment and bring the results with you.
  • Confirm any major allergies, especially if you have previously had an allergic reaction to a contrast agent.
  • Share if you are or may be pregnant, as your scan may need to be delayed or adapted.

How long does a CT scan with contrast take?

The CT scan itself takes little time, usually less than a minute. It takes much more time for the CT scanner to maneuver into the correct position for the scan. Positioning needs to be carefully calibrated, to prevent movement and to allow for each X-ray orientation. Usually, this part of the procedure takes between 30-60 minutes.

A CT scan with contrast takes longer. The contrast agent needs to be absorbed over time, whether it is administered orally, by IV, or rectally. The absorption process normally adds another 30 minutes to the total appointment time.

What happens during a CT scan of the abdomen?

When you get to the imaging clinic, you’ll remove all jewelry and metal objects. If you are having an intravenous contrast, an IV line will be inserted to deliver it. Otherwise, you might drink a barium suspension, or have the contrast inserted rectally. After the contrast is absorbed, you’ll lie on a table that will slide into the ring-shaped CT scanner. You may be strapped in to prevent movement.

The CT scanner will click as it moves and rotates around you. You’ll need to remain very still, and may even be asked to hold your breath for short intervals. Let the technician know if you have any discomfort, allergy symptoms or difficulty breathing. When all the views have been captured, the table will slide out of the CT scanner. If your contrast was administered by IV, your IV line will be removed.

You’ll be able to see, hear and communicate with the technician throughout the procedure. Don’t hesitate to let the technician know if you have any concerns or feel like you are experiencing any side effects from the contrast agent.

What are the side effects of contrast dye after a CT scan?

After the contrast is administered, some patients experience a flush of warmth, a metallic taste or a brief headache. If you take the contrast orally, you may feel slightly nauseous from the composition of the contrast agent, hence the recommendation to avoid eating beforehand.

In very rare cases, there is a risk of an allergic reaction. Allergic reactions range from mild to severe. Symptoms might include itching, a rash or hives, swelling, wheezing, shortness of breath or in extreme cases, anaphylaxis. The technician will monitor you throughout your CT scan, so communicate any allergic symptoms immediately.

What to do after a CT scan with contrast

If you have experienced an allergic reaction to the contrast agent, you might be monitored for a period of time after your CT scan. Otherwise, you do not need a recovery period, and will be cleared to resume your normal daily activities immediately.

To flush the contrast from your system, doctors recommend you drink plenty of water, 6-8 glasses over the day.

How do I access my CT scan results?

After your CT scan, PocketHealth can help you access your images and report as soon as they are issued by the hospital imaging department or clinic, often before your follow-up appointment with your doctor. Access your results here.

PocketHealth gives you fast, easy and secure access to your medical images and reports. You can use PocketHealth to store all your medical records in one place and can share your images in diagnostic quality with specialists or your healthcare team as needed.

What do my results mean?

CT images appear in shades of gray, from white to black. The shades reflect the density (or lucency) of each of your internal structures compared to the next. Dense structures appear lighter on CT scans, while lucent structures are darker. Bone, for instance, appears white, but lungs, which are full of air, are dark gray.

The Hounsfield scale measures tissue density and assigns a common scale to express how different tissues in your body absorb the radiation from the CT scan. The higher the number on the scale, the denser the tissue. Air registers at –1000 Hounsfield units (HU), for instance, while bone registers between 300-1000 HU.

Check out this complete guide to the terminology of your CT scan report for more details. When reviewing your report in PocketHealth, Report Reader can provide you with plain language definitions of the complex medical terms, helping you better understand your results ahead of your follow-up appointment.

One important thing to remember: when it comes to a CT scan report, ‘unremarkable’ is a good result.

Questions to ask during your follow-up doctor’s appointment

Even if you gain early access to your CT scan report through PocketHealth, you should always go over your results with your referring physician. You’ll want to ask questions during your follow-up appointment, such as:

  • Did my CT scan find anything of note?
  • Has anything changed?
  • Will I require any other follow-up imaging to clarify the results? If so, what kind?
  • What are the next steps in my treatment?

PocketHealth’s My Care Navigator highlights any follow-up recommendations made by the radiologist and can provide you with personalized follow-up questions that will allow you to have more fully informed conversations with your doctor at your follow-up appointment.

Advocate for your abdominal health

A CT scan can provide you and your healthcare team with valuable information about your abdominal health, especially if you are suffering from unexplained symptoms or pain. The more you understand about your body’s condition and progress, the more confidently you can take the next steps in your care journey.

PocketHealth gives you secure, fast access to your abdominal CT scan images and report so you can ask better questions and feel more confident to take those next steps.

How PocketHealth works

Learn how to use PocketHealth to securely access, better understand and share your CT scan results.

Access My Records