What small intestinal diseases can be examined by X-ray, CT, and MRI? What should we pay attention to?

Author: Jiang Tao, Chief Physician, Beijing Chaoyang Hospital, Capital Medical University

Reviewer: Gao Xianshu, Chief Physician, Peking University First Hospital

Small intestinal diseases are divided into inflammatory diseases, tumor diseases, and mechanical injury diseases, such as intestinal obstruction and intussusception.

1. What small intestinal diseases can be detected by X-ray, CT, and MRI?

The most important thing about a small intestine X-ray is to see whether there is intestinal obstruction; a small intestine X-ray contrast examination can comprehensively observe the function of the small intestine, whether there are inflammatory lesions in the intestinal mucosa, whether there are tumors, and can outline the details of the lesions, thus showing the changes in the intestinal mucosal structure well.

X-ray examinations require patients to repeatedly go to the examination bed for examination. Lesions are prone to overlap, the examination time is relatively long, and there will be some radiation.

Figure 1 Original copyright image, no permission to reprint

Small bowel CT angiography can not only detect intestinal obstruction and inflammation, but also thickening of the intestinal wall, lesions or tumors outside the intestinal wall, and traumatic diseases. CT is also an X-ray and has a certain amount of radiation.

Figure 2 Original copyright image, no permission to reprint

Small intestinal magnetic resonance imaging can not only comprehensively observe changes in the small intestinal wall, but also observe some changes on the outside of the intestinal wall. It can very clearly show lesions inside and outside the intestine. Currently, the international community recommends the use of magnetic resonance imaging for small intestinal examinations because it is radiation-free and safer. Basically all small intestinal diseases can be examined using magnetic resonance imaging.

Figure 3 Original copyright image, no permission to reprint

MRI can be used to examine inflammatory bowel diseases, such as Crohn's disease, repeatedly. It is very safe and has great advantages in the staging and treatment of inflammatory bowel diseases. If X-rays or CT scans are used repeatedly, the radiation will be relatively large.

2. Is it necessary to take a barium meal orally for a small intestinal X-ray examination?

If you just want to check whether there is intestinal obstruction, you can just take an X-ray without swallowing barium sulfate.

Except for intestinal obstruction, X-ray examination of small intestinal diseases requires swallowing a barium meal. Swallowing barium sulfate produces artificial contrast to observe the stomach and small intestine. Some diseases that could not be seen by X-rays before can now be observed by artificially introducing barium sulfate contrast agents.

It should be noted that you should eat liquid food the day before the small intestinal X-ray examination and do not drink water the next morning. After drinking the contrast agent, cooperate with the doctor and adopt a reasonable posture to do the examination, and you can go home after the examination.

3. Does small intestinal CT examination require oral contrast agent?

There are different ways to administer contrast agent in small bowel CT scans.

Gas can be used as an imaging contrast agent, which is to fill the small intestine with air so that the small intestine can be observed. A tube is passed through the mouth to the location of the Treitz ligament of the duodenum, and then air is pumped in. Generally, 1500-2000 ml of gas is injected. During this process, scopolamine is given to reduce intestinal peristalsis, which can better complete the examination.

You can also take contrast agents orally, such as drinking fat emulsion, which enters the small intestine for examination; for example, drinking mannitol, which is an isotonic contrast agent that can also fill the stomach and small intestine, and you need to drink about 2000 ml; for example, drinking iodine-containing contrast agents, you also need to drink 2000 ml, and the concentration is about 4%-5%. Contrast agents are generally taken in time periods, 500 ml every 15 minutes, until 2000 ml is finished, and then you can have the examination.

Before doing a small intestinal CT scan, we need to check whether the patient is allergic to iodine, whether he is planning to get pregnant, and whether he has hyperthyroidism. In these cases, iodine contrast agents cannot be injected. The purpose of intravenous injection of iodine contrast agents is to clearly show the blood vessels of the mesentery, to see the degree of intestinal wall enhancement, and to distinguish between intestinal inflammation and tumors; we also need to check whether the patient has contraindications to the use of scopolamine. For example, if the patient suffers from glaucoma or prostate disease, scopolamine can be omitted and the scan can be performed directly. The diagnostic effect will be slightly worse, but the small intestinal CT scan can still be completed.

CT scans require fasting, and you should not eat after dinner the day before, and you should not eat breakfast the next day. But you can't fast because when injecting iodine contrast agents, hydration is emphasized, that is, you should drink plenty of water before and after the injection, which is conducive to the excretion of the contrast agent.

4. What are the precautions for small intestinal magnetic resonance imaging?

Eat liquid food before the small intestinal MRI examination, and start fasting after dinner the day before the examination. Take polyethylene glycol to clean the intestines.

Before the MRI examination, you need to drink about 2000 ml of mannitol aqueous solution, 500 ml every 15 minutes. After drinking, use scopolamine to inhibit intestinal peristalsis, and then you can undergo a small intestine MRI examination.

There are no significant contraindications to MRI except in the presence of claustrophobia, hyperthermia, or an older-style pacemaker.

The preparation time for the small intestine MRI is about one hour, and the scanning time is about 15 minutes. There is nothing special to pay attention to after the test.