A 78-year-old female patient without any relevant past medical history presented with symptoms of epigastric abdominal pain, nausea and emesis. The laboratory assays showed no abnormalities.
Abdominal radiography shows a gas-containing colonic segment in the centre of the upper abdomen between the liver and the gastric air bubble. The caecum and ascending colon are not seen in their usual location.
Contrast-enhanced CT of the upper abdomen shows a dilated caecum in the lesser sac between the pancreas and the stomach, which is displaced anteriorly.
The terminal ileum and the ascending colon pass through the foramen of Winslow, between the portal vein in the hepatoduodenal ligament and the inferior vena cava.
At laparotomy performed 25 hours after CT the diagnosis of internal hernia through the foramen of Winslow with signs of ischaemia of the herniated caecum is made.
Abdominal internal hernias occur when there is a visceral protrusion through normal or abnormal apertures of the peritoneum or mesentery into a compartment in the abdominal cavity. [1, 2] The orifice can be congenital including normal or abnormal apertures arising from peritoneal defects; or acquired such as post-surgical, traumatic or post-inflammatory defects.  Internal hernias are rare, occurring in 0.2%–0.9% of autopsies and in 0.5%–4.1% of cases of intestinal obstruction.  Internal hernias can be classified by their location: paraduodenal, pericaecal, foramen of Winslow, transmesenteric and transmesocolic, pelvic and supravesical, sigmoid mesocolon, and transomental. 
Foramen of Winslow hernias constitutes 8% of all internal hernias, and most commonly involve the herniation of small intestine (60%–70%).  The terminal ileum, caecum, and ascending colon are involved in about 25%–30% of cases.  More rarely, transverse colon, omentum, and gallbladder can be involved.  This hernia can be sub-categorized as a congenital type, normal aperture subtype. 
Foreman of Winslow herniation predisposing factors include an enlarged foramen of Winslow and excessively mobile intestinal loops due to a long mesentery or persistence of the ascending mesocolon and an ascending colon that is not fused to the parietal peritoneum. 
Clinical diagnosis is difficult, as symptoms include epigastric discomfort, periumbilical pain, nausea and recurrent episodes of intestinal obstruction. [1, 2] Frequently, internal hernias are only clinical apparent when they are incarcerated, causing bowel obstruction and increased risk of serious complications, such as intestinal ischaemia. 
As clinical diagnosis of internal hernias is difficult, imaging studies play an important role.
In the past internal hernias were frequently assessed with conventional oral contrast studies, showing an encapsulation of distended bowel in an abnormal location, and evidence of obstruction with segmental distension and stasis. 
Nowadays, CT has become the first-line imaging technique because of its availability, speed, and multiplanar reformatting capabilities.
Foreman of Winslow CT features include the presence of distended intestinal segment located in the lesser sac, posterior to the liver hilum, anterior to the inferior vena cava, and between the stomach and pancreas, with tapering of the herniation through the foramen of Winslow.  There is anterior and lateral displacement of the stomach and stretching of the mesenteric vessels through the foramen of Winslow and absence of the ascending colon in the right gutter. 
Treatment is surgical and include resection of the involved bowel, versus caecopexy. 
CT allows an accurate and fast diagnosis of internal hernias and adequate surgical planning, avoiding irreversible damage to the bowel wall and mesentery.
Differential Diagnosis List
Foramen of Winslow internal hernia
Paraduodenal internal hernia
Foramen of Winslow internal hernia