Undulating Changeable Nature of Coils of Bowel Loops

A fan-shaped supporting ligament such as the mesentery, with an attachment of only 6 in. and an average length of 8-9 in., must suspend 20-22 ft of small bowel. This remarkable feat is accomplished by the unique plication or frilling of its intestinal border. The mesentery extends from its root in a series of fanlike ruffles. This geometric arrangement provides an unusually long border to suspend the jejunum and ileum. It is precisely this feature that contributes to the characteristic undulating nature of the coils of small intestine. The mesentery is of such a length that the loops are able to move freely in the abdominal cavity, and consequently the position occupied by any portion of the small bowel, with the usual exception of the beginning of the jejunum and the ending of the ileum, cannot be stated with certainty. Nevertheless, in general, the jejunum occupies the superior and left portions of the peritoneal cavity below the stomach, and the ileum the inferior and right divisions.

The changeable position ofj ejunal and ileal loops in vivo is most easily documented by comparing portions of the intubated small bowel on sequential films, as in Figure 14-8. These show the loops are movable on the root of the mesentery, but they maintain the convexities of the ruffles. Specific intestinal segments (nos. 1 through 4) can be matched and demonstrate varying positions within the peritoneal cavity. The changeable text continues on page 640

Fig. 14—2. Anatomy of the small bowel mesentery.

(a) Coronal anatomic section taken at the level of the third and fourth portions of the duodenum and the duodenojejunal junction (DJ). It demonstrates the fatty elastic nature of the mesentery, which contains the intestinal vessels as it radiates from its root to suspend loops of jejunum (JL) and ileum (I). L = liver. (Courtesy of Manuel Viamonte, M.D., Mount Sinai Hospital, Miami Beach, FL.; reproduced from Meyers.1)

(b) Transverse section shows fat-laden mesenteric leaves. Each sheath contains numerous vessels (arrowheads) radiating toward small bowel loops. These vessels can be traced back to the superior mesenteric vessel.

Root The MesenterySmall Bowel Mesentry Photo

Fig. 14—3. Dimensions of the small bowel mesentery.

The length of the intestinal border to an extent approximately 40 times that of its root is brought about by its unique frilled nature. This determines the characteristic formation of the small bowel into loops. (Reproduced from Meyers. )

Oblique Loop

Fig. 14—4. Two different cases of nonrotation of the jejunum in the right abdomen.

The oblique plane that provides the medial demarcation of the loops of bowel identifies the axis of the root of the small bowel mesentery (dashed line). (Reproduced from Meyers.1)

Fig. 14—4. Two different cases of nonrotation of the jejunum in the right abdomen.

The oblique plane that provides the medial demarcation of the loops of bowel identifies the axis of the root of the small bowel mesentery (dashed line). (Reproduced from Meyers.1)

Fig. 14—5. The root of the small bowel mesentery.

This is revealed as the oblique plane (arrows) from which the intestinal coils are suspended. In this instance, it provides a line of transition between jejunal loops (shown by their prominent valvulae conniventes), which project to the patient's left, and ileal loops (with less conspicuous valvulae), which extend to the right. (Reproduced from Meyers. )

Meyers LoopThe Root Small Bowel Mesentery

Fig. 14—6. Axis of the root of the small bowel mesentery.

Two different levels of CT, a 5 cm cephalad to b, in a patient with massive ascites, show rightward movement of the mesenteric root (MR) inferiorly. Consequently, the right infracolic space becomes smaller inferiorly. This favors the dynamics of metastatic seeding in the right lower quadrant in relation to distal ileal loops. AC = ascending colon; DC = descending colon.

(Courtesy of Yong Ho Auh, M.D., Asan Medical Center, Seoul, Korea.)

Fig. 14—6. Axis of the root of the small bowel mesentery.

Two different levels of CT, a 5 cm cephalad to b, in a patient with massive ascites, show rightward movement of the mesenteric root (MR) inferiorly. Consequently, the right infracolic space becomes smaller inferiorly. This favors the dynamics of metastatic seeding in the right lower quadrant in relation to distal ileal loops. AC = ascending colon; DC = descending colon.

(Courtesy of Yong Ho Auh, M.D., Asan Medical Center, Seoul, Korea.)

Obstructive Bowel Pattern

Fig. 14—7. Mechanical small bowel obstruction.

(a and b) Erect films in two different cases illustrate the "stepladder" arrangement of dilated obstructed loops. This pattern is related to tension anchored on the root of the mesentery.

Fig. 14—7. Mechanical small bowel obstruction.

(a and b) Erect films in two different cases illustrate the "stepladder" arrangement of dilated obstructed loops. This pattern is related to tension anchored on the root of the mesentery.

location is difficult to evaluate during routine contrast studies of the small intestine, chiefly because of the common inaccuracy in tracing the continuity of opacified, superimposed bowel loops.

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  • elanor brockhouse
    What is bowel loops in human body?
    2 years ago
  • timba
    What is biwl loop in human body?
    2 years ago

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