Internal Hernias Through the Foramen of Winslow

The greater peritoneal cavity communicates with the omental bursa (lesser peritoneal sac) through the epiploic foramen of Winslow. This potential opening is situated beneath the free edge of the lesser omentum, cephalad to the duodenal bulb and deep to the liver, and usually admits one and occasionally two fingers. In life, its anterior and posterior boundaries are usually in contact. The foramen may open to some extent when the

trunk is flexed, as in the sitting position. The omental bursa is limited in front by the stomach, lesser omentum, and the gastrocolic ligament, and behind by the posterior abdominal wall. Herniation of bowel through the foramen of Winslow accounts for 8% of all internal hernias.6,21 The small intestine alone is involved in the herniation in 60-70% of cases and the terminal small bowel, cecum, and ascending colon in 25-30%. Other viscera such as the transverse colon, omentum, or gallbladder are found occasionally.6,58,59

Predisposing causes include a common or abnormally long mesentery or persistence of the ascending meso-colon, permitting excessive mobility of the bowel and enlargement of the foramen.60 Alterations in intraabdominal pressure, including parturition, straining, and large meals, may tend to provoke the onset of the her-

niation, which may also be facilitated by an elongated right lobe of the liver directing the mobile intestinal loops toward the foramen of Winslow.61 The onset is usually acute, with severe progressive pain and signs of bowel obstruction. Some relief of pain may be achieved

with forward bending or the knee-chest position. The pressure and stretching of the common bile duct by her-niated colon may rarely produce an enlarged gallblad-der62 or jaundice.57

The characteristic plain film findings are demonstration of a circumscribed collection of gas-containing intestinal loops high in the abdomen medial and posterior to the stomach, associated with mechanical small bowel obstruction (Figs. 16-26 and 16-27). Distinction from other conditions that can present with gas in the lesser sac (e.g., perforated peptic ulcer or abscess) is possible by identification of the presence of a mucosal pattern and fluid levels within the herniated bowel. The fluid levels do not conform precisely to the anatomic recesses of the lesser omental cavity. If the colon is involved in the hernia, there may be a single air-fluid level, but several fluid levels may be present if a segment of small intestine is involved. The stomach is displaced to the left and anteriorly. Dilated small bowel loops generally de-

Omental Foramen

Fig. 16-26. Foramen of Winslow hernia.

Small bowel examination demonstrates marked dilatation of jejunum proximal to an obstruction in the right upper abdomen. The gas-containing herniated small bowel loops are visible within the lesser sac (arrows) medial to the stomach.

(Reproduced from Ghahremani and Meyers.16)

Fig. 16-26. Foramen of Winslow hernia.

Small bowel examination demonstrates marked dilatation of jejunum proximal to an obstruction in the right upper abdomen. The gas-containing herniated small bowel loops are visible within the lesser sac (arrows) medial to the stomach.

(Reproduced from Ghahremani and Meyers.16)

velop throughout the abdomen. When the cecum and ascending colon are involved in the hernia, the right iliac fossa appears empty,63-65 and interhaustral septa rather than valvulae conniventes may be identified within the herniated loop (Fig. 16-28). When the small intestine is the segment involved in the hernia, it can sometimes be identified progressing anterior to the hepatic flexure of the colon as it passes up to the foramen. Compression at this site then leads to distention of the ascending colon and cecum as well.

Barium studies readily confirm the diagnosis.57,61,64,66 The stomach is characteristically displaced anteriorly and to the left, and the first and second portions of the duodenum may also be displaced to the left63 (Figs. 16-27b, 16-29, 16-30). A small bowel series document the site of obstruction corresponding to the anatomic location of the foramen of Winslow between the duodenal bulb and the hilus of the liver. A barium enema study reveals obstruction with a tapered point near the hepatic flexure if the herniation contains the cecum and ascending colon57,61,65,68 (Figs. 16-30 and 16-31). If the

Left Colon Syndrome

Fig. 16—27. Cecal herniation through the foramen of Winslow.

(a) Supine abdominal film shows marked dilatation of the small bowel. An abnormal collection of gas is seen in the lesser peritoneal sac between the liver (L) and the stomach (S).

(b) Upper GI series reveals displacement of the stomach and the first and second parts of the duodenum to the left. There is less gas in the small intestine and within the lesser sac owing to partial spontaneous reduction of the hernia.

(Reproduced from Henisz et al.63)

small bowel alone is herniated, retrograde flow may be arrested in the transverse colon because of traction on the mesentery by the herniating small bowel.57,66

Computed tomography establishes the anatomic landmarks clearly (Figs. 16-32 through 16-34) and may document bowel and mesenteric changes precisely at the

Foramen Winslow Hernia

foramen of Winslow. The findings are readily distinguishable from the rare anatomic variant in adults of a retrogastric course of the transverse colon demonstrated by CT.70

The radiographic presentation may be complicated at times if there are associated defects in the gastrocolic or text continues on page 737

Fig. 16—28. Cecal herniation through the foramen of Winslow.

Plain film demonstrates gas-containing cecum with identifiable interhaustral septa within the lesser sac, displacing the stomach toward the left.

Foramen Winslow Hernia

Fig. 16—29. Foramen of Winslow hernia.

Delayed film from upper GI series demonstrates stretched terminal ileum ascending through the foramen of Winslow with the cecum and ascending colon within the lesser sac medial to the stomach.

(Reproduced from Schwartz and Feuchtwanger.67)

Radiology Foramen Winslow Images

Fig. 16—30. Foramen of Winslow hernia.

(a) Plain film shows mottled gas density consistent with large bowel impressing upon the lesser curvature of the stomach.

(b) Small bowel follow-through confirms herniation of the cecum and ascending colon into the lesser sac. Note the compression of the ascending colon at the foramen of Winslow (arrow).

(Reproduced from Goldberger and Berk.68)

Fig. 16—30. Foramen of Winslow hernia.

(a) Plain film shows mottled gas density consistent with large bowel impressing upon the lesser curvature of the stomach.

(b) Small bowel follow-through confirms herniation of the cecum and ascending colon into the lesser sac. Note the compression of the ascending colon at the foramen of Winslow (arrow).

(Reproduced from Goldberger and Berk.68)

Foramen Winslow Hernia

Fig. 16—31. Foramen of Winslow hernia.

(a) Barium enema shows failure of fixation of the right colon. The cecum and appendix arise into the right upper quadrant of the abdomen.

(b and c) Barium enema study and small bowel follow-through 4 years later. The cecum and ascending colon have herniated into the lesser sac, indenting the stomach. Compression of the ascending colon as it passes through the foramen of Winslow can be identified (arrows).

A large ovarian cyst that has developed since the preliminary study causes elevation and stretching of the sigmoid colon. This may have contributed to increased intraabdominal pressure and the formation of the interna! herniation.

(Reproduced from Goldberger and Berk.68)

Fig. 16—31. Foramen of Winslow hernia.

(a) Barium enema shows failure of fixation of the right colon. The cecum and appendix arise into the right upper quadrant of the abdomen.

(b and c) Barium enema study and small bowel follow-through 4 years later. The cecum and ascending colon have herniated into the lesser sac, indenting the stomach. Compression of the ascending colon as it passes through the foramen of Winslow can be identified (arrows).

A large ovarian cyst that has developed since the preliminary study causes elevation and stretching of the sigmoid colon. This may have contributed to increased intraabdominal pressure and the formation of the interna! herniation.

(Reproduced from Goldberger and Berk.68)

Lesser Sac

Fig. 16—32. Strangulated lesser sac hernia.

Dynamic contrast-enhanced CT demonstrates multiple dilated, fluid-filled loops of small intestine (S) in the lesser sac, between the stomach (St) and pancreas (P). The entrance of the mesenteric vascular pedicle with mesenteric fat is seen at the widened foramen of Winslow (arrow) behind the duodenum (d). Mesenteric edema and a small amount of lesser sac ascites are present.

(Courtesy of Jay Heiken, MD, Mallinckrodt Institute of Radiology, St. Louis, MO.)

Fig. 16—32. Strangulated lesser sac hernia.

Dynamic contrast-enhanced CT demonstrates multiple dilated, fluid-filled loops of small intestine (S) in the lesser sac, between the stomach (St) and pancreas (P). The entrance of the mesenteric vascular pedicle with mesenteric fat is seen at the widened foramen of Winslow (arrow) behind the duodenum (d). Mesenteric edema and a small amount of lesser sac ascites are present.

(Courtesy of Jay Heiken, MD, Mallinckrodt Institute of Radiology, St. Louis, MO.)

Fig. 16—33. Cecal herniation through the foramen of Winslow.

CT shows the opacified cecum in the lesser sac, between the liver, stomach, and pancreas.

Lower Left Quadrant Hernia Has HematomaForamen Winslow HerniaForamen Winslow

Fig. 16—34. Cecal herniation through the foramen of Winslow.

(a) Supine abdominal film demonstrates dilated loop of colon in the epigastrium with displacement of the stomach (S) to the left. Stool-filled bowel in the right lower quadrant (arrow) was originally thought to represent cecum.

(b) CT at the level of the celiac axis shows a collection of air in the lesser sac displacing the stomach (S) anteriorly and laterally. The collection has a beaklike projection (arrow) extending anterior to the inferior vena cava (IVC) and posterior to the portal vein (PV) and hepatic artery (HA). This tapered bowel loop is precisely at the foramen of Winslow.

(c) Water-soluble contrast enema confirms the location of the air-filled cecum in the lesser sac posteromedial to the nasogastric tube.

(Reproduced from Wojtasek et al. )

gastrohepatic omentum allowing reentry of the herni-

ated loops into the greater peritoneal cavity.

Unusual sites of entry into the lesser sac include the transverse mesocolon (see Fig. 16-47), gastrocolic ligament,71 and gastrohepatic ligament.72

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