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Splenic flexture constipation3/29/2023 ![]() ![]() The lumen tapers toward the site of stenosis, producing a pathognomonic beak sign ( Fig. On contrast enema examinations, the flow of contrast material ceases at the obstruction, and the rectum becomes distended. In sigmoid volvulus, a greatly inflated sigmoid loop appears as an inverted U-shaped shadow that rises out of the pelvis in a vertical or oblique direction, at times even reaching the level of the diaphragm ( Fig. Colonic volvulus typically presents with a massively dilated viscus extending into the upper abdominal quadrants. Because torsion of the bowel usually requires a long, movable mesentery, volvulus of the large bowel most commonly affects the cecum and sigmoid colon volvulus of the transverse colon occurs infrequently. Volvulus of the large bowel is the third most common cause of colonic obstruction. Abdominal radiograph shows obstruction caused by impaction of large amount of stool filling entire colon and rectum. The most common cause of colonic obstruction is a primary colorectal neoplasm, which often results in a characteristic apple-core narrowing of the colonic lumen on a contrast enema examination (Figs. Massive distention of the colon can compromise the mesenteric vascular supply, leading to strangulation and bowel necrosis. In intermittent or chronic obstruction, however, the cecal wall may become hypertrophied and the colon diameter may greatly exceed 10 cm without perforation. In acute colonic obstruction, the possibility of perforation is likely when the cecum distends to more than 10 cm. ![]() When the colon is massively distended by gas, perforation can occur. If the ileocecal valve is competent, the colon behaves like a closed loop, and the increased pressure caused by the obstruction cannot be dissipated. The major complication in colonic obstruction is perforation. Contrast-enhanced CT image in different patient shows dilated and stool-filled colon to level of obstructing mass ( arrow). If there is doubt, a barium enema or cross-sectional imaging is required to show the presence of an obstructing lesion or the patency of the colonic lumen (Figs. Distention of the rectum implies colonic ileus a collapsed rectum suggests mechanical obstruction. This position facilitates the entry of gas into the rectosigmoid and rectum, unless there is a mechanical obstruction at or above this level. In such cases, radiographs should be obtained with the patient in the lateral decubitus position (right side down). This transition is often impossible to detect in low colonic obstructions. In proximal colonic obstruction, the abnormal distention ends abruptly at the level of the lesion the colon distal to the lesion is free of gas. It is sometimes difficult to distinguish between a low colonic obstruction and colonic ileus. 2 ), often with cecal hypertrophy and thickening of the haustra and colon wall. If the ileocecal valve is incompetent, however, there is distention of gas-filled loops of both the colon and small bowel ( Fig. If the ileocecal valve is competent, obstruction causes a large dilated colon, with a markedly distended thin-walled cecum and little small-bowel gas ( Fig. The radiographic appearance of colonic obstruction depends on the competency of the ileocecal valve. Philadelphia, PA: Lippincott Williams & Wilkins, 2003) Clinical imaging: an atlas of differential diagnosis, 4th ed. (Reprinted with permission from Eisenberg RL. Because of incompetent ileocecal valve, there is diffuse dilation of gas-filled loops of both colon and small bowel, producing radiographic pattern that suggests adynamic ileus. 2 -Torsion of splenic flexure entering traumatic diaphragmatic hernia. ![]()
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