Normal radiographic anatomy of the small intestine

Normal small intestine

The most physiological method of artificial contrasting of the small intestine is oral contrasting, achieved by taking an aqueous suspension of barium sulfate orally. After passing the stomach and duodenum, the contrast mass enters the jejunum and then the ileum. 10-15 minutes after taking the barium, the shadow of the first loops of the jejunum is determined, and after 1-2 hours - the remaining sections of the small intestine.

The phases of filling the small intestine are recorded on radiographs. If it is necessary to accelerate the movement of the contrast mass, then strongly chilled barium is used, which is taken in separate portions, or additionally ice-cold isotonic sodium chloride solution. The effect of accelerating the passage of barium is also observed under the influence of a subcutaneous injection of 0.5 mg of prostigmine or an intramuscular injection of 20 mg of metoclopramide. The disadvantages of this method of examining the small intestine are the long duration of the procedure and the relatively high radiation load.

All oral methods of artificial contrasting have a significant drawback: the filling of the intestine is uneven, fragmentary, and individual segments are not visible on radiographs at all. As a result, based on the results of oral contrasting, one can only form an approximate idea of the morphological state of the small intestine.

The main method of radiographic examination (X-ray) of the small intestine is radiocontrast enteroclysm.

In this study, an extended intestinal tube (or a special catheter) is inserted into the duodenum of the patient under conditions of artificial drug-induced intestinal hypotension to ensure uniform and tight filling of the small intestine. 600-800 ml of an aqueous suspension of barium sulfate are poured through the tube. Normally, within 10-15 minutes, the contrast mass fills the entire small intestine and begins to enter the cecum. This makes it possible to study the morphological features of the jejunum and ileum. To improve visualization of the intestinal wall, air is dosed into the intestine after the barium suspension through the catheter, i.e. double contrasting of the small intestine is performed.

The loops of the jejunum are located mainly in the central sections of the abdominal cavity. They look like narrow bands 1.5 - 2 cm wide, the contours of the intestine are serrated, since narrow notches are evenly distributed on them - a reflection of the circular (Kerckring) folds of the mucous membrane. The folds themselves are distinguished as delicate transversely and obliquely directed stripes, the location and shape of which change with various movements of the intestinal loops. At the moment of passage of circular waves, the folds take a longitudinal direction. In general, the so-called feathery pattern of the relief of the inner surface is considered characteristic of the jejunum. The loops of the ileum are located lower, often in the pelvic area. Along the ileum, the serration of the contours becomes less and less and eventually disappears. The caliber of the folds decreases from 2-3 mm in the jejunum to 1-2 mm in the ileum.

The last loop of the ileum flows into the cecum. At the point of entry is the ileocecal valve (Bauhin's valve), its edges appear as semi-oval notches on the contour of the cecum. When observing intestinal loops using fluoroscopy, one can see their various movements that facilitate the movement and mixing of the contents: tonic contractions and relaxations, peristalsis, rhythmic segmentation, pendulum-like movements. In the ileum, as a rule, its segmentation is noted.

Absorption processes in the small intestine are studied using radionuclide techniques. If pernicious anemia is suspected, the absorption of vitamin B ₁₂ in the intestine is studied. For this, the patient takes the radiopharmaceutical: Co-B ₁₂ orally, with one of them associated with the intrinsic gastric factor (IGF), which is secreted by the gastric mucosa. In its absence or deficiency, the absorption of vitamin B ₁₂ is impaired. Then the patient is given a large amount of unlabeled vitamin B ₁₂ parenterally - about 1000 mcg. The stable vitamin blocks the liver, and its radioactive analogs are excreted in the urine. By collecting the urine excreted during the day and determining its radioactivity, it is possible to calculate the percentage of absorbed B _12. Normally, the excretion of this vitamin with urine is 10-50% of the administered dose. As noted above, the patient takes two radiopharmaceuticals. Since the radiation of the two cobalt radionuclides differs in its characteristics, this makes it possible to find out what is the basis for poor absorption of the vitamin - a deficiency of B12 or other reasons (impaired absorption in the intestine, genetically altered transport of vitamin B12 _by blood proteins, etc.).

Neutral fat and fatty acid absorption in the small intestine is assessed after the patient has ingested labeled trioleate-glycerol and oleic acid. This is most often used to determine the cause of steatorrhea, i.e. increased fat content in the stool. A decrease in the absorption of trioleate-glycerol indicates that steatorrhea is associated with insufficient secretion of lipase, an enzyme of the pancreas. The absorption of oleic acid is not impaired. Intestinal diseases impair the absorption of both trioleate-glycerol and oleic acid.

After taking these drugs, the patient's entire body is radiometrically measured twice: first without a screen, and then with a lead screen over the stomach and intestines. Radiometry is repeated after 2 and 24 hours. The absorption of trioleate-glycerol and oleic acid is judged by their content in tissues.

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