Regional Enteritis

The general radiologic findings ofregional enteritis correlate closely with the gross pathologic features. The involved bowel, often affected by "skip lesions," is sharply delimited from contiguous gut and has a narrowed lumen, which is sometimes strictured. The bowel wall is rigid and thick, the mesentery is often markedly thickened and edematous, and the mesenteric lymph nodes are enlarged. The swollen, inflamed mucosa develops a cobblestone appearance as longitudinal and transverse ulcers intersect. As these extend deeply through the wall, sinus tracts and fistulas may be present.

Other specific, more localized changes of regional enteritis have been observed surgically and pathologically. In their pioneering report in 1932, Crohn, Ginz-burg, and Oppenheimer noted on opening the intestine that a series of small linear ulcerations lying in a groove on the mesenteric side of the intestine is almost always present.27 It has also been observed that there is a close relationship between the destructive changes in the mucosa and the extent of increased mesenteric fat.28 The development of pseudodiverticula, furthermore, is probably related to eccentric skip areas.28

I have directly applied these discrete pathologic observations in regional enteritis to the radiologic alterations for a more definite diagnosis.1,2,29 The process may be identified, particularly in its early stages, as localized predominantly to the mesenteric borders of involved loops. Mesenteric border ulcers are a virtually pathog-nomonic finding in approximately 30% of patients with Crohn's disease.29 The findings ofmucosal irregularities, ulcerations, fixation and rigidity, sinus tracts, and extrinsic mass tumefaction may be confined or most evident on the concave margins (Figs. 14-31 through 1435). The linear ulcer along the concave border may extend over a few or many centimeters and can be continuous or interrupted. It may be accentuated by a thin line of radiolucency, which reflects inflammatory reaction and fibrosis underneath the ulcer.29 The fact that the antimesenteric wall may not be symmetrically involved at the same time but, rather, retains some degree of pliability may be revealed by the development of pseudosacculations from the convex border.

In severely involved loops, the segmental, skip nature of the lesions may result in pseudosaccular outpouchings from both the mesenteric and antimesenteric borders.

It follows that pseudosacculations or the appearance

Antimesenteric Border

Fig. 14—31. Regional enteritis.

Diffuse involvement of ileum. One loop demonstrates ulcerations and small sinus tracts along the concave, mesenteric border at the site of mesenteric tumefaction.

Pseudosacculations on the convex margin of the loop indicate that the antimesenteric border retains some pliability.

The dashed line indicates the axis of the root of the mesentery.

(Reproduced from Meyers.2)

Fig. 14—31. Regional enteritis.

Diffuse involvement of ileum. One loop demonstrates ulcerations and small sinus tracts along the concave, mesenteric border at the site of mesenteric tumefaction.

Pseudosacculations on the convex margin of the loop indicate that the antimesenteric border retains some pliability.

The dashed line indicates the axis of the root of the mesentery.

(Reproduced from Meyers.2)

Fig. 14—32. Regional enteritis in an 11-year-old male.

Small bowel series (a) with pressure spot film of distal ileum (b) show rigidity from the ul-cerative process clearly limited to the mesen-teric borders and pseudosaccular outpouch-ings from the more pliable antimesenteric margins.

(Reproduced from Meyers.2)

Fig. 14—32. Regional enteritis in an 11-year-old male.

Small bowel series (a) with pressure spot film of distal ileum (b) show rigidity from the ul-cerative process clearly limited to the mesen-teric borders and pseudosaccular outpouch-ings from the more pliable antimesenteric margins.

(Reproduced from Meyers.2)

Antimesenteric BorderMesenteric Enteritis

Fig. 14—33. Regional enteritis in two different cases.

(a and b) Flattening and rigidity are conspicuously localized to the mesenteric border of the terminal ileum. The antimesenteric border retains some pliability as shown by pseudosaccular outpouchings.

Small Bowel Series Crohns

Fig. 14—34. Regional enteritis.

(a) A linear ulcer (white arrows) can be clearly identified on the rigid mesenteric border of a diseased ileal loop. It is accentuated by a thin radiolucent line (black arrows) that reflects underlying inflammatory reaction and fibrosis. Pseudosacculations bulge from the antimesenteric border. The distal ileum is narrowed with the diffuse ulceronodular form of Crohn's disease.

(b) On another view, the linear ulcer (arrowheads) is seen en face. (Courtesy of Dean Maglinte, M.D., Indianapolis, IN.)

Fig. 14—34. Regional enteritis.

(a) A linear ulcer (white arrows) can be clearly identified on the rigid mesenteric border of a diseased ileal loop. It is accentuated by a thin radiolucent line (black arrows) that reflects underlying inflammatory reaction and fibrosis. Pseudosacculations bulge from the antimesenteric border. The distal ileum is narrowed with the diffuse ulceronodular form of Crohn's disease.

(b) On another view, the linear ulcer (arrowheads) is seen en face. (Courtesy of Dean Maglinte, M.D., Indianapolis, IN.)

Regional Enteritis

Fig. 14—35. Regional enteritis, with postsurgical recurrence.

(a) Striking linear ulcers on mesenteric borders (white arrows and black arrows) with pleated pseudosacculations on antimesenteric border.

(b) Nine years later, after surgical resection, there is evident recurrence. Hallmarks again include mesenteric linear ulceration (arrows) and antimesenteric outpouchings.

Fig. 14—35. Regional enteritis, with postsurgical recurrence.

(a) Striking linear ulcers on mesenteric borders (white arrows and black arrows) with pleated pseudosacculations on antimesenteric border.

(b) Nine years later, after surgical resection, there is evident recurrence. Hallmarks again include mesenteric linear ulceration (arrows) and antimesenteric outpouchings.

of diverticula limited solely to the mesenteric borders are not a feature of regional enteritis.

Another sign highly characteristic of Crohn's disease is also based on discrete radiologic-pathologic correlation. Contrast-enhanced spiral CT scans often show vascular changes in the mesentery, manifested as dilatation, tortuosity, and wide spacing of the vasa recta as they approach the mesenteric border of involved ileum. I have termed these distinctive changes the comb sign or vascular jejunization of the ileum30 (Fig. 14-36). Normally, the distal arterial arcades in the mesentery of the ileum are multitiered, so that the vasa recta that arise from the furthest arcade are numerous, short, and closely spaced. This arterial architecture is in contrast to the jejunum, where the vasa recta are longer and more widely spaced from each other. Increased mesenteric fat, termed fi-brofatty proliferation of the mesentery, accompanies transmural involvement of the bowel by Crohn's disease. The markedly dilated vessels pass through the hypertro-phied mesenteric and subserosal fat in which perivas-cular fibrosis develops31 (Fig. 14-37). The prominent vasa recta are seen by CT as elongated, widely spaced vessels. Identification of such hypervascularity indicates active disease and is useful in differentiating regional en teritis from lymphoma or metastases, which tend to be hypovascular lesions.30

Essentials of Human Physiology

Essentials of Human Physiology

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.

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