Left (75%): Protrusion of small bowel through paraduodenal mesenteric fossa of Landzert
Right (25%): Protrusion of small bowel through jejunal mesentericoparietal fossa of Waldeyer
• CT features
Left paraduodenal hernia
– Encapsulated “cluster” or sac-like mass of small bowel loops located between pancreatic body/tail and stomach to left of ligament of Treitz
– Hernia sac may exert mass effect on posterior wall of stomach, duodenojejunal junction inferiorly and medially, and transverse colon inferiorly/anteriorly
Very high (∼ 50%) lifetime risk of strangulation or incarceration
(Left) Graphic shows a left paraduodenal hernia containing dilated proximal jejunal loops in a peritoneal sac.
(Right) Small bowel follow-through demonstrates an ovoid cluster of mildly dilated jejunal segments in the left upper quadrant. The outer confines of the hernia sac are well defined. The herniated bowel exerts mass effect on the greater curvature of the stomach, characteristic of a left paraduodenal hernia.
(Left) Abdominal radiograph shows an unusual cluster of dilated jejunal small bowel loops in the left upper quadrant.
(Right) Axial CECT in the same patient shows the same cluster of dilated bowel interposed between the pancreas and stomach. Note the displaced inferior mesenteric vein that runs along the anterior edge of the hernia sac. This constellation of findings is characteristic of a left paraduodenal hernia.
TERMINOLOGY
Definitions
• Congenital internal hernia resulting from protrusion of bowel loops through abdominal mesenteric defect
IMAGING
General Features
• Best diagnostic clue
CECT: Cluster of dilated bowel loops in right or left upper abdomen with distorted mesenteric vessels
• Location
Left (75%): Protrusion of small bowel through paraduodenal (lateral to 4th part) mesenteric fossa of Landzert (located near ligament of Treitz)
Right (25%): Protrusion of small bowel through jejunal mesentericoparietal fossa of Waldeyer (located inferior to 3rd portion of duodenum)
Radiographic Findings
• Radiography
Supine abdomen: Distended, clustered loops of small bowel (SB) in right or left upper abdomen
CT Findings
• Left paraduodenal hernia
Encapsulated “cluster” or sac-like mass of small bowel loops located between pancreatic body/tail and stomach to the left of ligament of Treitz
– Bowel loops herniate into sac created by descending and distal transverse mesocolon
– Hepatic flexure of colon usually located anterior to hernia sac
Hernia sac may exert mass effect on posterior wall of stomach, duodenojejunal junction inferiorly and medially, and transverse colon inferiorly/anteriorly
Crowded, engorged mesenteric vessels supplying bowel loops within hernia sac
– Inferior mesenteric vein (IMV) and left colic artery lie in anterior and medial border of hernia sac, with IMV often displaced to left
• Right paraduodenal hernia
Clustered, encapsulated small bowel loops in right upper abdomen lateral and inferior to descending duodenum
– Ascending colon located lateral to hernia sac
– Mass effect from hernia sac displaces right ureter laterally
Unusual “looping” course of superior mesenteric artery (SMA) and vein (SMV) to supply bowel in hernia sac
– SMV rotated anteriorly and to left
– Twisted vascular jejunal branches behind SMA extend into hernia sac
– Main trunk of SMA and right colic vein located along anterior medial border of hernia sac
Commonly associated with intestinal nonrotation
• Small bowel obstruction (SBO)
Bowel loops within hernia sac may or may not be dilated depending on presence or absence of SBO, with transition point between dilated loops within hernia sac and decompressed distal small bowel
Consider bowel ischemia if bowel within hernia sac appears thickened, inflamed, or abnormally enhancing
Fluoroscopic Findings
• Small bowel follow-through
Abnormally crowded, clustered bowel loops in right or left upper abdomen with small bowel often absent from pelvis
– Left: Circumscribed ovoid mass of jejunal loops in LUQ lateral to ascending duodenum
– Right: Ovoid mass of small bowel loops lateral and inferior to descending duodenum
– Configuration of small bowel loops appears as sac-like “mass” with confining border
In cases with bowel obstruction (either complete or partial), point of transition between dilated and nondilated bowel may be visualized
Fixation, stasis, and delayed flow of contrast seen in bowel within hernia sac
– Right-sided paraduodenal hernias are often larger than on the left and herniated loops on right are typically more “fixed” than on left
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Left paraduodenal hernia
containing dilated proximal jejunal loops in a peritoneal sac.
of mildly dilated jejunal segments in the left upper quadrant. The outer confines of the hernia sac are well defined. The herniated bowel exerts mass effect on the greater curvature of the stomach, characteristic of a left paraduodenal hernia.
in the left upper quadrant.
interposed between the pancreas and stomach. Note the displaced inferior mesenteric vein 
that runs along the anterior edge of the hernia sac. This constellation of findings is characteristic of a left paraduodenal hernia.
Encapsulated “cluster” or sac-like mass of small bowel loops located between pancreatic body/tail and stomach to the left of ligament of Treitz
Clustered, encapsulated small bowel loops in right upper abdomen lateral and inferior to descending duodenum
Abnormally crowded, clustered bowel loops in right or left upper abdomen with small bowel often absent from pelvis
In cases with bowel obstruction (either complete or partial), point of transition between dilated and nondilated bowel may be visualized
