X-ray imaging uses a small amount of radiation to create pictures of structures inside the body. Contrast studies add a substance, such as barium or an iodine-based liquid, to make selected organs, blood vessels, or the digestive tract easier to see. Depending on the examination, contrast may be swallowed, given through a vein, or introduced through a tube. Preparation and risks vary by the test and your medical history.
What can X-ray imaging show?
X-rays pass through the body and produce images based on how different tissues absorb the radiation. Dense structures, such as bones, usually appear white, while air appears dark and soft tissues appear in shades of gray. These differences help healthcare professionals examine internal structures without surgery.
According to MedlinePlus, X-rays are commonly used to look for broken bones, examine the chest, and help identify certain injuries and health problems. They can also help locate foreign objects and check the position of some medical devices. The type of X-ray selected depends on the body area being examined and the medical question that needs to be answered.
A standard X-ray usually creates a still image. Some examinations use fluoroscopy, a technique that produces moving X-ray images in real time. Fluoroscopy can show how contrast material moves through the digestive tract or how certain structures function during the examination.
What is a contrast study, and how does it work?
A contrast study is an imaging examination that uses a contrast agent to make selected structures easier to distinguish from surrounding tissues. Contrast agents are sometimes called contrast media or contrast dyes, but they do not permanently color the body. They change how the imaging system displays a particular area. The contrast material itself does not produce radiation.
RadiologyInfo.org explains that barium sulfate and iodine-based contrast materials are commonly used in X-ray and related imaging examinations. Barium is often used to outline the digestive tract, while iodine-based contrast can help show blood vessels and internal organs. The material may be swallowed, given through a vein or artery, or introduced through the rectum, depending on the examination.
Contrast is not required for every X-ray. It is used when outlining a particular structure or improving the visibility of an area is likely to provide useful information. The choice depends on the examination, the information needed, and the person's medical history.
Which types of X-ray contrast studies are commonly performed?
Barium swallow and upper gastrointestinal studies
During a barium swallow, a person drinks a liquid containing barium while X-ray images show the movement of the material through the throat and esophagus. An upper gastrointestinal study may examine the esophagus, stomach, and first part of the small intestine. These tests can help clinicians assess the shape and movement of the upper digestive tract.
RadiologyInfo.org's guide to upper gastrointestinal X-rays describes how fluoroscopy allows the radiologist to watch the barium pass through the digestive system and capture images from different positions. The examination may be considered when investigating symptoms such as difficulty swallowing, upper abdominal discomfort, or possible problems with the passage of food.
Lower gastrointestinal contrast studies
A lower gastrointestinal contrast study, sometimes called a barium enema, uses contrast introduced through a small tube into the rectum to outline the colon. X-ray images can show the shape of the large intestine and help clinicians investigate selected bowel symptoms or structural changes. Preparation may include changes to the diet, fasting, or bowel-cleansing medication, depending on the examination.
Intravenous contrast studies and angiography
Some X-ray and fluoroscopy procedures use iodine-based contrast injected into a vein or artery. This can make blood vessels and selected internal structures easier to see. Angiography uses imaging to examine blood vessels and may be performed as part of a procedure involving a thin tube called a catheter. The method of giving contrast and the level of preparation required depend on the specific test.
How should you prepare for an X-ray with contrast?
Preparation varies with the body area and type of contrast being used. A routine X-ray may require little preparation, while a digestive tract study or an examination involving an injection may require additional instructions. The radiology department should explain what to do before your appointment. Do not fast, change prescribed medicines, or stop a medicine on your own unless your healthcare team instructs you to do so.
Before the examination, tell the healthcare professional arranging or performing it if any of the following apply:
- You have previously had a reaction to contrast material.
- You have other known allergies or have experienced a serious allergic reaction in the past.
- You have kidney disease, heart disease, diabetes, or a thyroid condition.
- You are pregnant, think you may be pregnant, or are breastfeeding.
- You take prescription medicines, non-prescription medicines, or supplements and are unsure whether any require special instructions.
These details help the imaging team decide whether additional precautions, a different contrast agent, or an alternative examination may be appropriate. RadiologyInfo.org's contrast-material guidance notes that previous reactions and certain medical conditions can affect preparation and safety decisions. Having one of these conditions does not automatically mean that contrast cannot be used.
What happens during the examination?
At the imaging department, a radiographer or other trained professional will explain the procedure and help you get into the required position. You may need to remove jewellery or clothing containing metal because these items can interfere with the images. The professional may ask you to stand, sit, or lie on an examination table and remain still while the pictures are taken.
If you are having a barium study, you may be asked to drink the contrast liquid. Its taste and texture can be unfamiliar. For a lower gastrointestinal study, contrast is introduced through a tube into the rectum, which can cause temporary fullness or an urge to pass stool. For an examination involving injected iodine-based contrast, a needle or small plastic tube is placed in a vein. You may briefly feel warmth, flushing, or a metallic taste in your mouth.
During fluoroscopy, the radiologist or radiographer may change your position or ask you to follow specific instructions so the contrast can be seen as it moves. You may be asked to hold your breath briefly to keep the images clear. The length of the procedure depends on the examination; the imaging team can give you a more specific estimate before it begins.
What happens after an X-ray contrast study?
Most people can return to their usual activities after a routine X-ray or contrast study unless they have been given different instructions, for example after sedation or another procedure. Follow the imaging team's advice about drinking fluids, eating, medicines, and any further observation that may be needed.
After a barium study, stools may look pale or white for a few days. Barium can also cause constipation or temporary changes in bowel movements. Drinking fluids as advised may help the contrast pass through the digestive tract. If you have a medical condition that limits fluid intake, follow your usual clinical advice rather than increasing fluids without guidance.
After an injection of iodine-based contrast, a brief warm sensation or metallic taste can occur. Less commonly, a person may develop a rash or other reaction after leaving the imaging department. Contact a healthcare professional if a new symptom persists or concerns you. Difficulty breathing, swelling of the throat or face, or other signs of a serious allergic reaction require immediate medical attention.
What are the risks of X-ray imaging and contrast material?
Radiation exposure
X-rays use ionizing radiation. Routine diagnostic examinations generally involve low doses, but the amount varies by the procedure and the area being examined. Radiation exposure carries a small potential long-term risk, so the decision to perform an examination considers the expected medical benefit and the need for the information it provides.
RadiologyInfo.org's radiation-safety guidance explains that imaging professionals use the lowest radiation dose needed to obtain useful images. If you have had many imaging examinations, mention this to your healthcare professional when discussing whether another test is needed.
Contrast-related reactions
Contrast materials are generally well tolerated, but side effects and adverse reactions can occur. Barium may cause nausea, stomach discomfort, or constipation. Iodine-based contrast can cause temporary warmth, flushing, nausea, itching, or a rash. Serious allergic reactions are uncommon, but the imaging team is trained to respond if one occurs.
People with severely reduced kidney function may need a particular assessment before receiving iodine-based contrast through a vein or artery because of the potential for worsening kidney function. Your healthcare team will consider the type of contrast, your medical history, and the expected benefit of the examination when deciding how to proceed.
Special considerations for children and pregnancy
Children require particular attention to radiation exposure because they are more sensitive to its potential effects than adults. Imaging professionals adjust the examination to the child's size and the information needed. An X-ray should be used when the expected benefit justifies the exposure, and the lowest suitable radiation dose should be selected.
For babies and young children who receive injected iodine-containing contrast, the U.S. Food and Drug Administration (FDA) has published recommendations for healthcare professionals to consider thyroid monitoring. Follow the child's care team's advice about whether any follow-up is needed.
If you are pregnant or may be pregnant, tell the imaging team before the examination. Pregnancy does not automatically rule out an X-ray, but the team needs to know so it can consider the body area being examined, the clinical need, and whether another imaging method would provide the necessary information with less risk.
How are the results interpreted?
A radiologist, a physician trained in medical imaging, reviews the X-ray images and prepares a report for the healthcare professional who requested the test. The report describes the findings visible on the images and may recommend further assessment if the pictures do not fully answer the clinical question.
Results are considered alongside your symptoms, medical history, examination findings, and any other relevant tests. An X-ray or contrast study can provide valuable information, but it does not answer every medical question. Your healthcare professional can explain what the results mean for your circumstances and whether any additional assessment is appropriate.