Quick answer: a CT of the abdomen and pelvis is one of the most common imaging tests. It helps find the cause of abdominal pain, such as appendicitis, diverticulitis or kidney stones, and is widely used to look for and follow cancers of the abdominal organs. You may be asked not to eat for a few hours beforehand, you may drink an oral contrast liquid at the center before the scan, and you may also get IV contrast. The scan itself takes seconds; the visit can take a couple of hours if you need oral contrast.
Abdominal CTs are a large part of a typical day in a CT department, from emergency patients with sudden pain to people coming in for their regular cancer follow-up. Here is what the test shows and how to get ready for it.
What does an abdominal CT show?
A CT of the abdomen and pelvis shows the organs, bowel, blood vessels, bones and soft tissues of the belly and pelvis in detail. Doctors use it to help diagnose:
- infections and inflammation, such as appendicitis, diverticulitis, kidney infection (pyelonephritis) and abscesses
- inflammatory bowel disease, such as Crohn’s disease and ulcerative colitis
- pancreatitis
- cancers of the liver, bowel, kidneys, pancreas, adrenal glands, uterus, ovaries and bladder, as well as lymphoma and melanoma, and spread of cancer from other parts of the body
- kidney and bladder stones
- abdominal aortic aneurysm
- injuries to the spleen, liver, kidneys and other organs after trauma
It is also used to guide biopsies and drainages, plan and check surgery, plan radiation therapy and monitor cancer treatment.
What it does not show well
- Gallstones: CT may not see them well. Ultrasound is the best test for gallstones. See [link: Abdominal Ultrasound: How to Prepare].
- Some liver, kidney, pancreas, uterus and ovary problems are better evaluated with MRI.
- Babies with acute belly problems are usually examined first with x-rays, contrast studies or ultrasound.
With or without contrast?
Abdominal CTs can be done in different ways depending on the question:
| Type | When it is often used |
|---|---|
| No contrast | For example, to look for kidney stones |
| IV contrast | Most scans looking at organs, infection, inflammation or cancer |
| Oral + IV contrast | When the bowel needs to be clearly outlined, for some specific questions |
Not every abdominal CT needs oral contrast. Evidence has been moving away from routine oral contrast when IV contrast is used, so many centers reserve it for specific questions. Your doctor and the radiologist decide.
How to prepare
- Fasting: your doctor may tell you not to eat or drink for a few hours beforehand. Follow the exact instructions.
- Tell your doctor about any previous contrast reaction, allergies, kidney disease, diabetes and medications. If you have a known contrast allergy, your doctor may prescribe medication beforehand.
- Pregnancy: abdominal and pelvic CT is generally avoided in pregnancy unless medically necessary. Always tell the team if you might be pregnant.
- Clothing: loose, comfortable clothes without metal; you may change into a gown.
- Kidney blood test: you may need a recent one if you are getting IV contrast.
The full checklist is in [link: How to Prepare for a CT Scan With Contrast].
The oral contrast drink
If your scan needs oral contrast, you usually drink it at the center before the scan, in portions over about an hour or more, so it can travel through the bowel. Protocols differ: one university hospital uses drinks at 60 and 30 minutes before the scan, and another clinic scans about 90 minutes after the drink. If your scan includes the pelvis, some centers ask you to avoid urinating between drinking the contrast and the scan.
Most people find the taste mildly unpleasant but easy to tolerate.
From the scanner room: [TU EXPERIENCIA: cómo es el contraste oral en tu práctica (sabor, cantidad, tiempo) y trucos que funcionan para tomarlo. Qué dudas tienen los pacientes en la sala de espera.]
What happens during the scan
- You lie on your back on the CT table, usually with your arms raised above your head so they do not interfere with the images.
- If you are getting IV contrast, it is injected through a small IV in your arm. You may feel warm, notice a metallic taste or feel as if you need to urinate. These sensations pass quickly. See [link: CT Contrast Side Effects: What Is Normal and What Is Not].
- You will be asked to hold your breath for a few seconds while the table moves through the scanner.
- Sometimes the scan is repeated a few minutes after the injection to see the organs at different moments.
The full walkthrough is in [link: What to Expect During a CT Scan].
How long does it take?
The scanning takes seconds to a few minutes, and the exam is usually done within 30 minutes. With oral contrast, plan for a much longer visit, often a couple of hours. See [link: How Long Does a CT Scan Take?].
Risks
- Radiation: CT uses x-rays. There is always a slight chance of cancer from excessive radiation exposure, but the benefit of an accurate diagnosis outweighs the risk. Doses are tailored, especially for children. See [link: How Much Radiation Is in a CT Scan?].
- Contrast: serious allergic reactions to iodine contrast are extremely rare, and departments are equipped to handle them.
- Breastfeeding: in general, there is no need to stop breastfeeding after an abdominal CT.
Getting your results
A radiologist analyzes the images and sends a report to your doctor. In an emergency, results are often available quickly; for routine scans, your doctor will go over them with you. You may need a follow-up exam to look more closely at a finding or to check for changes over time.
Tips from the technologist
[TU EXPERIENCIA: 3-4 consejos propios. Ideas: no orinar después del contraste si te lo indican, ropa sin cremalleras, avisar de dolor al levantar los brazos, llevar algo para entretenerse.]
Frequently asked questions
Can an abdominal CT detect cancer?
It is often the best method for detecting and following many cancers in the abdomen and pelvis. A diagnosis usually also needs other tests, such as a biopsy.
Can a CT scan show kidney stones?
Yes. CT is commonly used to look for kidney and bladder stones, often without contrast.
Does an abdominal CT show the gallbladder?
It shows the gallbladder, but it may miss gallstones. Ultrasound is the best test for gallstones.
Do I have to drink contrast for an abdominal CT?
Not always. It depends on what the doctor is looking for and the center’s protocol.
Can I eat after an abdominal CT?
Yes. You can return to your normal diet and activities right away, and drinking extra fluids helps clear the contrast.
This article is for general information and does not replace advice from your doctor or imaging team.
Sources
- RadiologyInfo.org (ACR and RSNA): Abdominal and Pelvic CT
- RadiologyInfo.org (ACR and RSNA): How to Prepare for Your CT Exam
- Michigan Medicine: CT Preparation Instructions
- Christie Clinic: Abdomen/Pelvis CT patient instructions
- Compass Oncology: CT Scan Prep Guide
- WikEM: Oral contrast for abdominal and pelvic CT