Normal X-ray anatomy of the colon and rectum

Conventional images do not provide a clear image of the colon and rectum. If images are taken after the patient has taken an aqueous suspension of barium sulfate orally, the passage of the contrast mass through the digestive tract can be recorded. From the terminal loop of the ileum, the barium passes into the cecum and then sequentially moves to the remaining sections of the colon. This method, the "contrast breakfast" method, is used only to assess the motor function of the colon, but not to study its morphology. The fact is that the contrast contents are distributed unevenly in the intestine, mixed with food waste, and the relief of the mucous membrane is not displayed at all.

The main radiological method for examining the colon and rectum is their retrograde filling with a contrast mass - irrigoscopy.

In this examination, careful preparation of the patient for irrigoscopy is very important: a low-residue diet for 2-3 days, taking laxatives - one tablespoon of castor oil at lunch the day before, a series of cleansing enemas - the evening before and early in the morning on the day of the examination. Some radiologists prefer preparation with special tablets, such as contact laxants, which promote the rejection of feces from the intestinal mucosa, as well as the use of laxative suppositories and magnesium sulfate.

An aqueous barium suspension is introduced through the anus using a Bobrov apparatus in the amount of 600-800 ml. The position, shape, size, outline, and mobility of all sections of the colon and rectum are assessed. The patient is then asked to empty the colon. As a result, the bulk of the contrast suspension is removed from the intestine, and the barium coating remains on the mucous membrane and outlines its folds.

After studying the relief of the mucous membrane, up to 1 liter of air is blown into the colon under fluoroscopy control. This makes it possible to assess the extensibility (elasticity) of the intestinal walls. In addition, against the background of stretched folds of the mucous membrane, the slightest irregularities, such as granulation, polyps, and small cancerous tumors, are better distinguished. This method is called double contrasting of the colon.

In recent years, the method of simultaneous double contrasting of the colon has become widespread. In this study, a relatively small amount of contrast mass is first introduced into the intestine - about 200-300 ml, and then, under the control of transillumination, air is carefully and dosedly injected, thus pushing the previously introduced bolus of barium suspension proximally, up to the ileocecal valve. Then a series of overview radiographs of the abdominal organs in standard positions are made, supplementing them with individual images of the intestinal area of interest. A mandatory condition for conducting a study using the primary double contrasting method is preliminary drug-induced intestinal hypotension.

The large intestine occupies mainly the peripheral parts of the abdominal cavity. In the right iliac region is the cecum. At its lower pole, the vermiform appendix in the form of a narrow channel 6-10 cm long is often filled with a contrast mass. The cecum passes without sharp boundaries into the ascending colon, which rises to the liver, forms the right bend and continues into the transverse colon. The latter is directed to the left, forms the left bend, from which the descending colon goes along the left lateral wall of the abdominal cavity. In the left iliac region, it passes into the sigmoid colon, forming one or two bends. Its continuation is the rectum, which has two bends: the sacral, with the convexity facing backward, and the perineal, with the convexity facing forward.

The cecum has the largest diameter; in the distal direction the diameter of the colon generally decreases, increasing again at the transition to the rectum. The contours of the colon are wavy due to haustra constrictions, or haustra. When the colon is filled orally, the haustra are distributed relatively evenly and have smooth, rounded outlines. However, the distribution, depth, and shape of the haustra change due to the movements of the intestinal contents and the movements of the intestinal wall. During irrigoscopy, haustra are less deep and in places imperceptible. On the inner surface of the intestine, the haustra correspond to the semilunar folds of the mucous membrane. In those sections where the contents are retained longer, oblique and transverse folds predominate, and in those sections that serve to remove feces, narrow longitudinal folds are more often visible. Normally, the relief of the intestinal mucosa is variable.

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