British Journal of Radiology (2008) 81, e50-e52
© 2008 British Institute of Radiology
doi: 10.1259/bjr/20661338
Lesser sac herniation through a defect in the transverse mesocolon: CT findings
Z-Y LIU, MD
1
Y WANG, MD
2 and
C-H LIANG, MD
1
1 Department of Radiology, Guangdong Provincial People's Hospital No. 106, 2 Department of Medical Ultrasonics, First Affiliated Hospital, Sun Yatsen University No. 58, Zhong Shan Er Lu, Guangzhou, Guangdong 510080, China
Correspondence: Professor Chang-Hong Liang, Radiology, Guangdong Provincial People's Hospital No. 106, Zhong Shan Er Lu, Guangzhou, Guangdong 510080, China. E-mail: dr_chhliang{at}yahoo.com.cn
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Abstract
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We herein report a case of lesser sac herniation through a defect in the transverse mesocolon. In addition to CT signs suggestive of bowel obstructions, there are some characteristic CT findings in this extremely rare type of internal herniation, which include clustering of distended jejunal segments directly compressing the pancreas, displacement of the stomach anterolaterally, displacement of the transverse colon anteriorly and a normal appearance around the foramen of Winslow.
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Case report
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A 48-year-old woman was admitted to our hospital with severe epigastric pain and distension for 1 day. She also complained of nausea, vomiting and obstipation. She had no history of previous abdominal trauma or surgery. Physical examination revealed epigastric tenderness and abdominal distension with hypoactive bowel sounds. A diagnosis of acute bowel obstruction was suspected and abdominal CT with intravenous contrast media was performed for further evaluation. The scout image (Figure 1
) showed a vague soft-tissue mass in the epigastrium, displacing the stomach and transverse colon. Further contrast-enhanced CT images (Figure 2) revealed that distended loops of fluid-filled proximal jejunum protruded into the lesser sac, anterior to the head, body and tail of the pancreas. There was no fat or other tissue intervening between the pancreas and the herniated jejunum. The stomach was displaced anterolaterally, and the compressed transverse colon anteriorly. The gastro-splenic ligament was seen lateral to the distended intestinal loops. The foramen of Winslow appeared normal. Additional imaging findings included the displacement and twisting of the mesentery and mesenteric vessels with generalized ascites.
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Figure 1. Supine CT scout image reveals a tissue mass-like lesion in the upper mid-abdomen (white arrows) displacing the stomach and transverse colon.
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Figure 2. Axial image of the intravenous contrast-enhanced abdominal CT scan shows jejunal loops herniated into the lesser sac, interposed between the stomach and the pancreas. The fluid-filled jejunal loops displace the stomach anterolaterally (white arrow) and the gastro-splenic ligament laterally. They compress the posteromedial aspect of the transverse colon (curved arrow) and the anterior aspect of the pancreas (black arrow). The foramen of Winslow is normal (arrowhead). Ascites is seen over the liver.
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With a diagnosis of acute intestinal obstruction, this patient underwent emergency exploratory laparotomy. Surgery revealed a 3 cm defect in the transverse mesocolon, near the spleen, with 80 cm of jejunum herniating through the defect into the lesser sac (Figure 3). The jejunal segment was twisted through one and a half turns. There was more than 800 ml of bloody and feculent ascites in the peritoneal cavity. The herniated jejunum was ischaemic and surgical resection was necessary. The patient had an uncomplicated postoperative course.
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Figure 3. Schematic diagram in the sagittal plane showing the anatomy of the herniation. The small bowel(SB) herniated through a defect (arrowhead) in the transverse mesocolon (TM) into the lesser sac (LS). The dashed arrows indicate the herniating pathway. CL, caudal lobe; LO, lesser omentum; FW, foramen of Winslow; HSB, herniated small bowel; P, pancreas; ST, stomach; D, duodenum; TC, transverse colon; GO, greater omentum.
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Discussion
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Internal hernias are infrequent and account for only approximately 4% of intestinal obstructions [1]. Lesser sac herniations, constituting only 0.4–3.0% of internal hernias, are extremely rare [2, 3]. The causes of lesser sac herniations include congenital defects in, or atrophy of, the omentum and dilation of the foramen of Winslow, and possibly increased abdominal pressure plays a role in the development of herniation [2, 4]. The clinical signs and symptoms of lesser sac hernia are non-specific and include abdominal pain, nausea, vomiting and distension. These rare lesser sac herniations can be lethal. For this reason, immediate diagnosis and surgery is essential. However, the preoperative diagnosis can be a challenge for both radiologist and surgeon. The diagnosis of lesser sac hernia is usually not established until laparotomy or autopsy [5]. The value of imaging in the diagnosis has been documented in the literature, but no specific imaging features have been proposed.
According to the literature, lesser sac herniations can be classified into three basic types according to the site of the aperture [5–7]. Type 1 is a foraminal hernia through the foramen of Winslow, type 2 is a hernia through a defect in the lesser or greater omentum, and type 3 is a hernia through a defect in the transverse mesocolon. Type 3 is usually secondary to abdominal trauma or prior abdominal surgery with the creation of a Roux-en-Y loop [4, 8, 9]. Herniated bowel loops into the lesser sac may re-enter into the greater cavity through another aperture, such as the foramen of Winslow or a defect in the omentum or transverse mesocolon [7].
The plain film appearances of lesser sac herniation include fluid-distended bowel loops in the upper abdomen [10], with or without air–fluid interfaces. In the scout image in our patient, a dense mass in the epigastrium displaced the adjacent viscera. This mass occupied the region of the lesser sac.
CT scanning can play an important role in the diagnosis of lesser sac herniations [11]. The findings are similar to those of other internal hernias and include bowel obstruction, clustering of the herniated bowel loops with stretching and displacement of the mesenteric vessels, displacement of the adjacent viscera and sometimes volvulus. Intestinal ischaemia is often present, as evidenced by oedema of the bowel wall and ascites.
The CT findings specific for a lesser sac herniation are the interposition of distended jejunal loops between the stomach and the pancreas with displacement of the stomach anteriorly and direct compression on the head, body and tail of the pancreas. No fat or other structures are found between the pancreas and the distended jejunum. The gastro-splenic ligament is displaced laterally to the distended intestinal loops. In our patient, the normal appearance of the foramen of Winslow excluded a foraminal lesser sac herniation. The herniated jejunum was confined within the lesser sac. There were no distended bowel loops anterior to the antrum and body of the stomach and the transverse colon, so lesser sac herniation through a defect in the lesser or greater omentum [7] was unlikely. Thus, in our patient, herniation into the lesser sac via a defect in the transverse mesocolon was suggested.
In conclusion, the CT findings suggestive of lesser sac herniation through a defect in the transverse mesocolon include: (1) clustering of distended jejunal segments directly compressing the pancreas; (2) displacement of the stomach anterolaterally; (3) displacement of the transverse colon anteriorly; and (4) a normal appearance around the foramen of Winslow.
We can find no previous case of a lesser sac hernia through a defect in the transverse mesocolon that was unrelated to a history of prior abdominal trauma or surgery. The constellation of CT signs we have described in this case should suggest the diagnosis of lesser sac herniation through a defect in the transverse mesocolon.
Received for publication September 23, 2006.
Revision received November 13, 2006.
Accepted for publication November 15, 2006.
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References
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Abstract
Case report 
