Computed tomography (CT) is a type of medical imaging tool that allows doctors to see inside a person’s body.
Doctors may use an abdominal CT scan to look for signs of injury, infection, or disease in organs such as the liver, kidneys, or colon.
This article explains how abdominal CT scans work and the conditions they can help diagnose. It also outlines what preparations to make before having a CT scan and what to expect during the procedure.
A CT scan or CAT scan is a type of medical imaging procedure that doctors may use to view bones, organs, and soft tissues inside a person’s body.
The CT scanner uses a thin beam of radiation to scan the body from many different angles. It then feeds the scanned images into a computer, which creates individual slices, or cross-sections, of the inside of the body. The American Cancer Society likens these cross-section images to the individual slices of a loaf of bread.
A CT scanner can also layer all the scanned images on top of one another to create a 3D image of the scanned body area. Specialist doctors called radiologists can then rotate the 3D image on a computer screen, to view it from different angles.
Doctors may use a CT scan to help diagnose the cause of pain in the abdomen or pelvic area. Some conditions that may cause pain in these areas include:
- internal abscesses
- kidney stones
- bladder stones
- infections, such as appendicitis and pyelonephritis
- the inflammatory bowel diseases ulcerative colitis and Crohn’s disease
- problems with the pancreas, such as pancreatitis
- problems with the liver, such as cirrhosis
- spleen, liver, or kidney injury
- abdominal aortic aneurysms
- cancers of the liver, kidneys, pancreas, bladder, or ovaries
Other potential uses for a CT scan include:
Below is some information on what people can expect before and during their abdominal CT scan.
Before the scan
Below are some procedures that people may need to follow before they go in for their CT scan.
When diagnosing bowel conditions, a doctor will need a clear view of the inside of a person’s bowel. As such, they may tell a person to avoid eating or drinking for several hours before their scan. Alternatively, a person may receive a laxative or enema to clear out the bowel.
Taking a contrast dye
In some cases, doctors will ask a person to take a contrast dye before their CT scan. The dye helps the internal organs and blood vessels show up more clearly on the scan. A person may take the dye orally or receive it through a vein or an enema.
The contrast dye is not suitable for everyone. People should tell their healthcare team if they are pregnant or have ever experienced an allergic reaction to any of the following:
- contrast dye
Removing metal objects
Before having a CT scan, a person will need to undress and put on a gown. They will also need to remove any metal objects, as these can interfere with the CT images. Such objects may include:
- underwired bras
- belts with metal belt buckles
Anyone who has an implanted medical device, such as a pacemaker or infusion port, should tell their healthcare team about the device before the scan.
During the scan
A CT scanner is a large, donut-shaped machine with a tunnel in the middle where the scanning takes place. A person lies on a flat table that slides in and out of the tunnel. Sometimes, the medical team may use pillows or straps to keep the person in the correct position, while the scan is taking place.
The person will need to stay perfectly still for the duration of the scan, which usually only takes a few minutes. It does not hurt, but some people may find it uncomfortable to stay still for this amount of time.
Some people have concerns about the potential risks of CT scans. We outline two key concerns below.
Increased cancer risk
Some people worry that CT scans will increase their risk of developing cancer. This is because CT scanners use a form of ionizing radiation to image the inside of the body.
It is worth remembering that a CT scan only delivers a low dose of radiation, and the cancer risk is small. According to the National Cancer Institute, not having the procedure can be much riskier than having it. This is especially so if a doctor is using the CT scan to help diagnose cancer or another serious condition.
Contrast dye allergies
Some people may experience a reaction to the contrast dye they take before the CT scan. The side effects are usually mild. However, they can be severe in rare cases.
Potential mild side effects include:
Potential severe side effects include:
- reddening of the skin
- swelling of the throat and airways
- difficulty swallowing or breathing
- fast heartbeat
- bluish skin discoloration called peripheral cyanosis
Anyone who experiences any severe side effects should tell their healthcare team straight away.
To help avoid the risk of side effects, people should tell their doctor if they:
- are pregnant or breastfeeding
- have any allergies, including hay fever
- are taking any medications or herbal supplements
- have any medical conditions, such as:
- have had any recent illnesses or operations
A radiologist will interpret the results of a person’s CT scan and will send a written report to the person’s doctor. The doctor will ask the person to make a follow-up appointment to discuss the results of the scan and talk about next steps.
Sometimes, a person may need a follow-up CT scan so the doctor can further explore or monitor any abnormalities they identified in the initial scan.
A CT scan is a medical imaging tool that allows doctors to see bone, organs, and soft tissues inside a person’s body. Doctors may use an abdominal CT scan to look for signs of injury, infection, or disease in organs such as the colon, spleen, liver, or kidneys.
A CT scan usually takes only a few minutes. The procedure does not hurt, but some people may find it uncomfortable to lie still for the duration of the scan.
A doctor will usually receive the results of a CT scan within a few days. People will need to make a follow-up appointment with their doctor to discuss the results of the scan. They can also take this opportunity to talk through their diagnosis and any treatments they may need.