Transverse Mesocolon and Duodenocolic Ligament

The root of the transverse mesocolon extends across the infraampullary segment of the descending duodenum, the head of the pancreas, and continues along the lower edge of the body and tail of the pancreas anteriorly to bear continuity with the splenorenal and phrenicocolic ligaments6,56 (Fig. 4-41). Near the uncinate process of the pancreas it becomes confluent as well with the root of the small bowel mesentery. These bare areas thus establish anatomic planes of continuity between (a) the pancreas and (b) the transverse colon up to the anatomic splenic flexure, the spleen, and small bowel loops. The very beginning of the peritoneal reflections on the right, known as the duodenocolic ligament, further establishes continuity to the descending duodenum and posterior hepatic flexure.6,57

The transverse mesocolon inserts in relation to the taenia mesocolica, and correlative studies have established that the preferential spread of pancreatic lesions along this mesentery is to the inferior border of the transverse colon41,42 (Figs. 4-42 through 4-45). The haustral pattern on the uninvolved, pliable superior border may be thrown into a pseudosaccular appearance. Circumferential growth may develop, although usually the degree of invasion and fixation is not as extensive as may occur from indurated carcinoma of the stomach. Nevertheless, the greater involvement of the posteroin-ferior margin of the transverse colon on a barium enema study generally indicates the pancreas as the primary site. Rarely, similar changes may be encountered from seeded metastases on the greater omentum58 (Fig. 4-46).

On CT, the transverse mesocolon is identified as the fatty plane extending from the pancreas, particularly at the level of the uncinate process, to the ventrally situated transverse colon with the middle colic vessels coursing through it (Figs. 4-47 and 4-48). In cases of pancreatic carcinoma, masslike or dendritic spread through the me-socolon can be precisely localized (Figs. 4-49 through 4-51).

Getting Barium Dendritic

Fig. 4—39. Gastrocolic fistula secondary to carcinoma of the transverse colon.

Barium enema demonstrates that the small primary lesion has established a malignant fistulous tract along the gastrocolic ligament (arrows). (Reproduced from Meyers and McSweeney.1)

Fig. 4—39. Gastrocolic fistula secondary to carcinoma of the transverse colon.

Barium enema demonstrates that the small primary lesion has established a malignant fistulous tract along the gastrocolic ligament (arrows). (Reproduced from Meyers and McSweeney.1)

The gastrocolic trunk, which enters the superior mesenteric vein at the level of the uncinate process, may be used as a vascular landmark on CT scans of the pancreas, representing the root of the transverse mesocolon as it becomes confluent with the root of the small bowel mesentery.60

These same ligaments provide mesenteric planes for direct extension to and from other sites. As the hepatic flexure of the colon crosses anterior to the descending duodenum, the two structures are in very close anatomic relationship, separated only by the duodenocolic ligament, constituting the short beginning of the transverse mesocolon6 (Fig. 4-52). In this way, the paraduodenal area may be involved by direct spread from an infiltrating carcinoma of the hepatic flexure across the beginning reflection of the transverse mesocolon6,57,61-63 (Figs. 453 and 4-54). Carcinomas of the right colon are notoriously clinically occult, and the palpation of an epigastric or right upper quadrant mass in such a patient may lead to radiologic investigation being initiated with an upper GI series (Fig. 4-54a). This may be very misleading unless the underlying anatomic relationships are kept in mind and a barium enema study undertaken.

Direct lymphatic extension along the draining chain of lymph nodes may be identified occasionally by barium studies.6,64 By its relationship to the central lymph nodes draining the colon, the duodenum may reflect changes of lymph node spread from a remote carcinoma of the colon. The lymphatic vessels draining the colon parallel the arterial supply. Those draining the right side of the colon are located near the origin of the superior mesenteric artery, in close relationship to the superior border of the horizontal (third) portion of the duodenum (Fig. 4-52). Those draining the distal transverse and descending colon are partially located in the transverse mesocolon and near the ascending left colic branch of the inferior mesenteric artery, which courses lateral to the ascending (fourth) portion of the duodenum. By radiologically recognizing these changes of nodal impressions upon the superior contour of the third portion

Fig. 4-40. Spread of pancreatic carcinoma into the gastrocolic ligament.

CT coronal reconstruction shows extensive tumor involvement (T) of the gastrocolic ligament between the stomach (S) and transverse colon (C) following invasion of the transverse mesocolon by a carcinoma of the tail of the pancreas. (Reproduced from Heiken et a!.55)

Fig. 4-40. Spread of pancreatic carcinoma into the gastrocolic ligament.

CT coronal reconstruction shows extensive tumor involvement (T) of the gastrocolic ligament between the stomach (S) and transverse colon (C) following invasion of the transverse mesocolon by a carcinoma of the tail of the pancreas. (Reproduced from Heiken et a!.55)

Transverse MesocolonSplenorenal Ligament Pancreas

Fig. 4—41. The transverse mesocolon: anatomic relationships and planes of spread.

(a) Frontal drawing showing the relationships of the transverse mesocolon (TM) and its continuity with the small bowel mesentery (SBM), the splenorenal ligament (SRL), and the phreni-cocolic ligament (PCL).

(b) Lateral diagram. The arrowed-dashed lines show the planes of spread from the pancreas (P) to the transverse colon (TC) and small bowel (SB). (Reproduced from Meyers et al.9)

Mesocolon TacHallux Valgus Deformity

Fig. 4—42. Sagittal section through the transverse colon.

Extension of a malignancy from the pancreas (P) through the transverse mesocolon spreads preferentially downward along the TM-TL haustra toward the TO-TL row. This constitutes the inferior border of the transverse colon. S = stomach; TM = taenia mesocolica; TO = taenia omentalis, TL = taenia libera. (Reproduced from Meyers et al.42)

Fig. 4—42. Sagittal section through the transverse colon.

Extension of a malignancy from the pancreas (P) through the transverse mesocolon spreads preferentially downward along the TM-TL haustra toward the TO-TL row. This constitutes the inferior border of the transverse colon. S = stomach; TM = taenia mesocolica; TO = taenia omentalis, TL = taenia libera. (Reproduced from Meyers et al.42)

Taenia Mesocolica

Fig. 4—43. Extension of carcinoma of the pancreas along the transverse mesocolon.

Barium enema documents flattening and fixation along the inferior border of the transverse colon (arrows).

Pancreas Transverse Section

Fig. 4—44. Carcinoma of the pancreas with direct invasion of the transverse colon along the mesocolon.

The major extension is typically along the inferior contour (arrows), where multiple nodules are present.

Transverse Mesocolon

Fig. 4—45. Carcinoma of the pancreas extending along the transverse mesocolon.

This results in fixation and large mass along the inferior border of the transverse colon.

(Reproduced from Meyers and McSweeney.1)

Haustra Barium Enema

Fig. 4—46. Seeded metastatic ovarian carcinoma on the greater omentum.

Barium enema shows multinodular infiltration of the inferior border of the transverse colon (arrows).

(Reproduced from Krestin et al.58)

of the duodenum (Fig. 4-55) or upon the lateral aspect of the duodenojejunal junction (Fig. 4-56), it is possible to determine the extent of a colonic carcinoma preop-eratively or the development of lymph node metastases postoperatively.6,64 CT clearly verifies these pathways.63,65 (Figs. 4-57 through 4-60). Rarely, postoperative lymph node metastases may undergo necrosis and become manifest as duodenoduodenal fistulas66 (Figs. 461 and 4-62).

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  • Cara
    How is the duodenocolic ligament formed?
    8 months ago

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