Sigmoid Colon Radiologic Features

The sigmoid mesocolon reflects obliquely off the level of the left sacroiliac joint to suspend the redundant sig-moid loops anteriorly. It forms an inverted V with its apex located at the division of the left common iliac artery. The left portion descends medial to the left psoas major muscle.107,108 The right segment descends into the text continues on page 205

Sigmoid Colon Mesentery

Fig. 4—115. Ascitic fluid collecting between mesenteric folds.

(a and b) CT documents ascitic fluid pooling between the folds of the small bowel mesentery. The latter are seen as lucent bands, reflecting their adipose nature, with their contained vessels radiating from the root (R) to opacified loops of jejunum (J) and ileum (I).

Fig. 4—115. Ascitic fluid collecting between mesenteric folds.

(a and b) CT documents ascitic fluid pooling between the folds of the small bowel mesentery. The latter are seen as lucent bands, reflecting their adipose nature, with their contained vessels radiating from the root (R) to opacified loops of jejunum (J) and ileum (I).

Mesenteric Root And Leaves

Fig. 4-116. Relationships of small bowel mesentery to pooled ascites.

CT in a patient with a large amount of ascites and peritoneal thickening shows multiple mesenteric leaves that are separated from each other clearly by thickened peritoneum and pools of ascites. Linear vessels course with the fat-laden mesenteric leaves that display U-shapes reflecting their ruffled nature as they extend from the evident broad-based root. SB = small bowel, M = mesentery.

Fig. 4-116. Relationships of small bowel mesentery to pooled ascites.

CT in a patient with a large amount of ascites and peritoneal thickening shows multiple mesenteric leaves that are separated from each other clearly by thickened peritoneum and pools of ascites. Linear vessels course with the fat-laden mesenteric leaves that display U-shapes reflecting their ruffled nature as they extend from the evident broad-based root. SB = small bowel, M = mesentery.

Fig. 4—117. The flow of ascites forms a series of pools within the recesses of the small bowel mesentery.

The most consistent drainage is to its lower end, in relation to distal ileal loops and the cecum. (Reproduced from Meyers.4)

Fig. 4—118. Seeded gastric carcinoma along lower small bowel mesentery.

There is palisaded separation of ileal loops in the right lower quadrant (arrows). Mucosal folds are mildly tethered. (Sites of obstruction are also present proximally.) (Reproduced from Meyers.4)

Sigmoid Colon Rewrapped The Ovary

Fig. 4—119. Seeded ovarian carcinoma along lower small bowel mesentery.

There is striking scalloped displacement of multiple ileal loops in the right lower quadrant, following the axis of the mesenteric recesses. The mucosal folds are mildly tethered. (Reproduced from Meyers and McSweeney.1)

Sigmoid Colon Mesentery

Fig. 4—120. Seeded ovarian carcinoma along lower small bowel mesentery.

Nodular serosal masses on the mesenteric borders of distal ileal loops are associated with fibrotic narrowing and angulation. These produce some proximal obstruction.

Fig. 4—120. Seeded ovarian carcinoma along lower small bowel mesentery.

Nodular serosal masses on the mesenteric borders of distal ileal loops are associated with fibrotic narrowing and angulation. These produce some proximal obstruction.

Fig. 4-121. Seeded pancreatic carcinoma along lower small bowel mesentery.

Mass separation and striking angulation of fixed ileal loops in right lower quadrant from extensive desmoplastic reaction.

(Reproduced from Meyers.4)

Fig. 4-121. Seeded pancreatic carcinoma along lower small bowel mesentery.

Mass separation and striking angulation of fixed ileal loops in right lower quadrant from extensive desmoplastic reaction.

(Reproduced from Meyers.4)

Psammomatous Calcification Ovaries

Fig. 4-122. Seeded ovarian carcinoma along lower small bowel mesentery.

Two masses with psammomatous calcifications in the right lower quadrant displace ileal loops and press on the ascending and transverse colon. (Reproduced from Meyers and McSweeney.1)

Fig. 4-122. Seeded ovarian carcinoma along lower small bowel mesentery.

Two masses with psammomatous calcifications in the right lower quadrant displace ileal loops and press on the ascending and transverse colon. (Reproduced from Meyers and McSweeney.1)

Fig. 4-124. Seeded pancreatic carcinoma along lower small bowel mesentery.

T2-weighted MR image shows a metastatic deposit in the right lower quadrant (arrows), displacing bowel loops. (Reproduced from Semelka et al.59)

Psammomatous Calcification Ovaries Cancer Larynx Images

Fig. 4—125. Seeded ovarian carcinoma along lower small bowel mesentery.

Metastatic masses (M) compress the ileocecal region and an adjacent ileal loop. There is early tethering of mucosal folds. Asci-tes is present.

Psammomatous Calcification Colon

Fig. 4-126. Seeded carcinoma of the gallbladder along lower small bowel mesentery.

This results in a mass eccentrically indenting the medial contour of the cecum (open arrows). There is also direct mvasion of the transverse colon (black arrows). (Reproduced from Meyers.4)

Fig. 4-127. Seeded gastric carcinoma along lower small bowel mesentery.

Lobulated mass indents the inferior contour of the cecum (arrows). The distal ileum is angulated and deformed by mass impressions.

(Reproduced from Meyers.4)

Fig. 4-127. Seeded gastric carcinoma along lower small bowel mesentery.

Lobulated mass indents the inferior contour of the cecum (arrows). The distal ileum is angulated and deformed by mass impressions.

(Reproduced from Meyers.4)

Lower Colon Black

Fig. 4-128. Seeded pancreatic carcinoma along lower small bowel mesentery.

Large lobulated mass with nodular excrescences grossly indents the inferior contour of the cecum (arrows). There is also mass pressure on the terminal ileum with fibrous angulation.

(Reproduced from Meyers.4)

Fig. 4-128. Seeded pancreatic carcinoma along lower small bowel mesentery.

Large lobulated mass with nodular excrescences grossly indents the inferior contour of the cecum (arrows). There is also mass pressure on the terminal ileum with fibrous angulation.

(Reproduced from Meyers.4)

Fig. 4-129. Seeded ovarian carcinoma along lower small bowel mesentery.

Annular mass narrowing of apex of cecum.

(Reproduced from Meyers.4)

Intersigmoid Recess

pelvis and ends at the level of the third sacral vertebra. Considerable fat is normally present within the sigmoid mesocolon, allowing visualization of sigmoid and superior rectal vessels, which course between the two peritoneal layers (Fig. 4-132). Ascitic fluid and thus metastatic seeding commonly collect adjacent to the sig-moid mesocolon in the "intersigmoid" recess.

Lodgment and growth of deposits arrested along the barrier of the sigmoid mesocolon in the left lower quadrant result in changes characteristically localized to the superior border of the sigmoid colon (Figs. 4-133 through 4-135). The associated desmoplastic reaction causes tethering of the mucosal folds. These lose their axis normally perpendicular to the lumen of the bowel and become angulated, often toward a common point in the mesentery at the site of the secondary lesion (Figs. 4-136 through 4-138). Even when annular invasion from the seeded metastases has occurred, the sigmoid colon tends to show preponderant changes on its su perior border (Figs. 4-139 and 4-140). This localization occurs in more than 20% of cases of metastatic seeding.

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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