The plane of attachment of the small bowel mesentery may be drawn by an imaginary line extending from the midtransverse duodenum or duodenojejunal junction to the ileocecal junction. The root of the mesentery most often inserts at the termination of the ileum with the colon and only rarely on the ascending colon or the distal ileum. On plain films, the line may be drawn from the left of L2 to the right sacroiliac articulation.
The axis of the root may be defined more clearly by barium contrast studies, which then relates more directly to small bowel loops. Figure 14-4 illustrates two differ ent cases of nonrotation of the jejunum, a common developmental variant. The root of the small bowel mesentery is shown by the oblique plane providing the medial demarcation of these jejunal loops. The root may also be identified in cases of normal development and fixation of the mesentery. In the small bowel series shown in Figure 14-5, the attached border of the mesentery can be appreciated as the oblique plane from which the loops are suspended. The axis can be readily appreciated by sectional imaging (Fig. 14-6).
It is these normal relationships of small bowel loops to the supporting mesentery that basically determine the radiologic findings in cases of mechanical obstruction. The dilated loops are then each tensely suspended from the mesenteric root as peristalsis persists; the hydrody-namic consequences lead to the classic "stepladder" configuration (Fig. 14-7).
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.