IS Case 44: Internal Hernia through the Foramen of Winslow
Imaging Sciences URMC 2008
Publication Date: 2009-05-19
A barium enema (Fig. 1) demonstrates obstruction with focal narrowing of the ascending colon near the hepatic flexure. Overhead images (Fig. 2) from the barium enema demonstrate contrast within a large dilated midline structure, corresponding to the herniated cecum. The ascending colon traverses abnormally toward the midline. A NG tube is identified anterolaterally within the collapsed stomach. CT scan (Figs. 3 and 4) shows a large air-filled structure along the midline, representing the herniated cecum within the lesser sac. The lesser sac is posterior to the liver, anterior to the inferior vena cava and between the stomach and pancreas. There is a tapered narrowing through the foramen of Winslow. The stomach is displaced laterally.
The foramen of Winslow is a normal communication between the greater and lesser peritoneal cavities. It is located beneath the free edge of the hepatoduodenal ligament. Herniation of bowel through the foramen of Winslow accounts for 8% of all internal hernias. Of these, 60-70% contain only small bowel while 25-30% contain cecum and ascending colon. Risk factors for this type of hernia include an abnormally long small-bowel mesentery or persistence of the ascending mesocolon, both of which allow excessive bowel mobility. An enlarged foramen of Winslow or an elongated right hepatic lobe (such as a Riedel's lobe) are also thought to be predisposing factors. Most patients are middle-aged and present with acute onset obstructive symptoms. Once the internal herniation is identified, the treatment is surgical.
Foramen of Winslow hernias often present with a similar radiographic appearance to that of left paraduodenal hernias. One key feature that can be useful in distinguishing between these entities is the location of the entry point. Usually, it is somewhat superior and to the right of the spine with foramen of Winslow hernias, whereas the point of narrowing is more posterior and to the left of the spine in left paraduodenal hernias.
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