Transmesenteric and Transmesocolic Hernias

About 5-10% of all internal hernias occur through defects in the mesentery of the small intestine.12'13'21 An etiologic relationship to prenatal intestinal ischemic accidents seems probable' because in infants with atretic intestinal segments such defects and herniation are frequently associated.14 In fact, nearly 35% of these hernias occur in the pediatric age group' in which they constitute the most common type of internal hernias.8'14 In adults, however' most mesenteric defects serving as the

Small Mesenteric Hernias

Fig. 16-39. Persistent descending mesocolon.

The ileal loops opacified by reflux during barium enema examination occupy the left paracolic gutter. The descending colon (arrows) is displaced toward the midline. The presence of a probable defect in the mesocolon is not yet verified surgically in this patient. (Reproduced from Ghahremani and Meyers.16)

Fig. 16-39. Persistent descending mesocolon.

The ileal loops opacified by reflux during barium enema examination occupy the left paracolic gutter. The descending colon (arrows) is displaced toward the midline. The presence of a probable defect in the mesocolon is not yet verified surgically in this patient. (Reproduced from Ghahremani and Meyers.16)

hernial ring are probably the result of previous surgery, abdominal trauma, or intraperitoneal inflammation.12,13 The mesenteric defects are often located close to the ligament of Treitz or the ileocecal valve. The rather small size of the defect (usually 2-5 cm) and the absence of a limiting hernial sac account for a relatively high incidence of strangulation and intestinal gangrene, with a mortality rate ofabout 50% for surgically treated patients and 100% for those without surgical treatment.12

Radiographs of the abdomen usually demonstrate mechanical small bowel obstruction and, occasionally, a single distended "closed loop," with perhaps apposition of the afferent and efferent limbs (Fig. 16-40). The small bowel series or barium enema study with reflux may further assist in the diagnosis by showing a constriction around the closely approximated afferent and efferent loops of the herniated intestine73,74 (Fig. 16-41). These findings invariably signal a surgical emergency, although clinical and radiologic differentiation of the hernia from small bowel volvulus or entrapment beneath peritoneal

Trans Mesenteric Hernia

Fig. 16-40. Transmesenteric hernia.

Herniation of a jejunal loop through a defect in the small bowel mesentery. Note the typical presentation of a distended closed loop (straight arrows) with approximation of its ends at the hernial orifice (curved arrows). (Reproduced from Ghahremani and Meyers.16)

Fig. 16-40. Transmesenteric hernia.

Herniation of a jejunal loop through a defect in the small bowel mesentery. Note the typical presentation of a distended closed loop (straight arrows) with approximation of its ends at the hernial orifice (curved arrows). (Reproduced from Ghahremani and Meyers.16)

Fig. 16—41. Transmesenteric hernia.

Herniation of the distal ileum through a congenital defect in the mesentery of a Meckel's diverticulum. Barium enema study with reflux shows constriction around the closely approximated afferent and efferent loops (arrows) of the ileum.

(Reproduced from Dalinka et al.74)

Transmesenteric Hernia

Fig. 16—42. Partial volvulus through mesenteric defect.

A postsurgical defect in the mesentery provides the site for an internal hernia. Volvulus is indicated by the crossing of the afferent and efferent limbs at the point of obstruction (arrows).

(Reproduced from Maglinte et al.75)

Fig. 16—42. Partial volvulus through mesenteric defect.

A postsurgical defect in the mesentery provides the site for an internal hernia. Volvulus is indicated by the crossing of the afferent and efferent limbs at the point of obstruction (arrows).

(Reproduced from Maglinte et al.75)

adhesions may be impossible.16 Volvulus of the herniated loops may be shown by crossing of the involved limbs at the point of obstruction75 (Fig. 16-42). Computed tomography displays the relationships of the herniated loops (Fig. 16-43) and may reveal complications (Fig. 16-44). Even if the mesenteric defect itself is not recognized, disclosure of the mesenteric vascular pedicle may be diagnostic for internal hernia (H. Mori, personal communication). Arteriography may reveal an abrupt change in the course of the superior mesenteric artery and displacement of the visceral branches, indicating an internal hernia with the site of the herniation sug gested by the change in the course of the vessels77,78 (Fig. 16-45).

Defects in the transverse mesocolon may rarely provide access for internal herniation of small bowel loops posterior to the transverse colon into the lesser sac7,79,80 (Figs. 16-46 and 16-47). Although these defects may result from trauma, inflammation, or operative procedures, most are probably congenital in origin. Since the orifice is usually very large with an avascular space in the base of the mesocolon, many loops may herniate without strangulation, gangrene, or even significant obstruction. Reentry into the greater peritoneal cavity is frequent, via the routes of the foramen of Winslow, the gastrohepatic ligament, and the gastrocolic ligament81 (Fig. 16-48).

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Transmesenteric Hernia

Fig. 16—43. Transmesenteric hernia.

(a) Small bowel series shows a peculiar grouping of small bowel loops in the lower abdomen (arrows).

(b) CT demonstrates these multiple loops are circumscribed within a transmesenteric hernial sac (arrows). (Reproduced from Miller et al. )

Fig. 16—43. Transmesenteric hernia.

(a) Small bowel series shows a peculiar grouping of small bowel loops in the lower abdomen (arrows).

(b) CT demonstrates these multiple loops are circumscribed within a transmesenteric hernial sac (arrows). (Reproduced from Miller et al. )

Fig. 16-44. Strangulated transmesenteric hernia.

Almost all the jejunal loops have herniated through a large defect of the small bowel mesentery and twisted, with resultant necrosis.

CT after administration of intravenous contrast demonstrates (a) normal proximal jejunal loops (arrows), a markedly distended fluid-filled loop of twisted jejunum (J), and (b) superior mesenteric artery and vein with abrupt angulation at the twisted site (open arrows) with dilated collateral veins (curved arrow). (Courtesy of Hiromu Mori, MD, Oita Medical University, Oita, Japan.)

Fig. 16-44. Strangulated transmesenteric hernia.

Almost all the jejunal loops have herniated through a large defect of the small bowel mesentery and twisted, with resultant necrosis.

CT after administration of intravenous contrast demonstrates (a) normal proximal jejunal loops (arrows), a markedly distended fluid-filled loop of twisted jejunum (J), and (b) superior mesenteric artery and vein with abrupt angulation at the twisted site (open arrows) with dilated collateral veins (curved arrow). (Courtesy of Hiromu Mori, MD, Oita Medical University, Oita, Japan.)

Twisted Small Intestine Surgery

Fig. 16-45.Transmesenteric hernia.

Arteriogram in a 48-year-old female with acute abdominal symptoms shows an abrupt change in the course of the superior mesenteric artery, which is seen to fold back on itself. The terminal ileal and ileocolic branches course in a twisting fashion toward the left upper quadrant and fan toward the right flank instead of distributing in the normal lower abdominal course from the left to the right.

At surgery, herniation of the entire right colon and half of the small bowel with a twist through a 10-cm congenital defect in the small bowel mesentery was found. This was reduced manually and the defect closed.

(Reproduced from Cohen and Patel.77)

Fig. 16-45.Transmesenteric hernia.

Arteriogram in a 48-year-old female with acute abdominal symptoms shows an abrupt change in the course of the superior mesenteric artery, which is seen to fold back on itself. The terminal ileal and ileocolic branches course in a twisting fashion toward the left upper quadrant and fan toward the right flank instead of distributing in the normal lower abdominal course from the left to the right.

At surgery, herniation of the entire right colon and half of the small bowel with a twist through a 10-cm congenital defect in the small bowel mesentery was found. This was reduced manually and the defect closed.

(Reproduced from Cohen and Patel.77)

Transmesenteric Hernia

Fig. 16-46. Transmesocolic hernia into the lesser sac.

(a and b) CT demonstrates thatjejunal loops along with their mesenteric fat and vessels (arrows) have herniated into the lesser sac through a defect of the transverse mesocolon. St = stomach. (Courtesy of Hiromu Mori, MD, Oita Medical University, Oita, Japan.)

Fig. 16-46. Transmesocolic hernia into the lesser sac.

(a and b) CT demonstrates thatjejunal loops along with their mesenteric fat and vessels (arrows) have herniated into the lesser sac through a defect of the transverse mesocolon. St = stomach. (Courtesy of Hiromu Mori, MD, Oita Medical University, Oita, Japan.)

Colon Herniation Through Lesser Sac

Fig. 16-47. Transmesocolic hernia into the lesser sac.

(a) Prone and (b) oblique radiographs demonstrate multiple small bowel loops above and posterior to the displaced stomach. They have entered the lesser sac through a large defect in the transverse mesocolon. (Reproduced from Meyers and Whalen.80)

Fig. 16-47. Transmesocolic hernia into the lesser sac.

(a) Prone and (b) oblique radiographs demonstrate multiple small bowel loops above and posterior to the displaced stomach. They have entered the lesser sac through a large defect in the transverse mesocolon. (Reproduced from Meyers and Whalen.80)

Fig. 16-48. Transmesocolic hernia.

(a) Supine and (b) lateral radiographs demonstrate virtually the entire small bowel loops have herniated through a large defect in the transverse mesocolon into the lesser sac. They have then bulged anteriorly into or through the gastrocolic ligament to displace the transverse colon inferiorly and posteriorly. (Courtesy of Alan Herschman, M.D., New Brunswick, NJ.)

Fig. 16-48. Transmesocolic hernia.

(a) Supine and (b) lateral radiographs demonstrate virtually the entire small bowel loops have herniated through a large defect in the transverse mesocolon into the lesser sac. They have then bulged anteriorly into or through the gastrocolic ligament to displace the transverse colon inferiorly and posteriorly. (Courtesy of Alan Herschman, M.D., New Brunswick, NJ.)

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