CT colonography – obtaining layered sections of anatomical structures of the colon using a computed tomograph. Allows you to assess the condition of the colon without endoscopic examination and detect volumetric neoplasms in it. After scanning, the layered sections are subjected to computer processing, which makes it possible to obtain a virtual three-dimensional anatomical model of the large intestine (the so-called virtual colonoscopy).
Virtual CT colonography is prescribed for bloody discharge in the feces, pain in the colon, causeless weight loss, increased weakness and fatigue, as well as unstable stool with alternating diarrhea and constipation – these signs may be the first symptoms of colorectal cancer. The examination is required to clarify the data obtained as a result of other diagnostic manipulations (irrigoscopy, colonoscopy), or if there are contraindications to cavity contrast and invasive techniques, for example, in the case of a general severe condition or the severity of the inflammatory process. The technique is used in the diagnosis of intestinal obstruction to establish its level and causes. For prophylactic purposes, CT is indicated for people over 45-50 years of age and patients with a burdened heredity for malignant neoplasms of the large intestine.
X-ray tomography is not prescribed for pregnant women and children, and is also not recommended for patients with hyperkinesis (movements during the study reduce the quality of images), although in the latter case it is possible to conduct an examination under anesthesia. Contraindications to intravenous contrast are chronic renal failure and a history of severe allergic reactions to iodine. CT Colonography is not performed in patients with decompensated diabetes mellitus and heart failure, it is not performed in severe bronchial asthma and hyperthyroidism. Cavity contrast is contraindicated in the active stage of inflammatory processes.
Preliminary examination may include laboratory tests, abdominal X-ray examination and other diagnostic procedures. Before tomography with contrast, kidney function is clarified in advance. The patient begins preparation for the procedure in 2-3 days.
- Products that increase gas formation (legumes, black bread, dairy products, etc.) are excluded from the diet.
- Intestinal cleansing is supplemented by taking special preparations based on macrogol.
- A cleansing enema is performed the day before. Taking activated charcoal and antispasmodics is usually recommended 1-2 hours before CT colonography.
The examination is performed on an empty stomach. If necessary, a system for intravenous administration of contrast fluid is pre-installed, the allergological history is clarified, skin allergy tests are carried out.
Methodology of conducting
Virtual CT colonography is performed on an outpatient basis or during inpatient treatment. The recommended position of the patient is lying on his back, during the scan the patient may be asked to turn on his stomach and back for better visualization. During the study, it is possible to inject gas (to straighten the intestinal wall) and a contrast agent through the anus. If necessary, to assess the condition of the vessels, contrast is administered intravenously. The duration of the study is 15-30 minutes. Some images are taken while holding your breath, as the radiologist informs you in advance via a two-way communication system.
At the time of administration of contrast fluid, the patient may feel dizziness, a rush of heat, a metallic taste in the mouth. Complications develop in 1-3% of the subjects and include nausea, vomiting, sore throat, cough, etc. More severe forms of reactions to iodine-containing contrast are rare, the necessary drugs are available in the office for their relief. CT results are prepared within a few hours (up to a day). The patient receives printed pictures with a written interpretation. Additionally (optionally or if necessary), data is recorded on a digital medium.