Health& Medicine

1. Radiological Imaging of Abdominal Internal Hernias.
Dr/ ABD ALLAH NAZEER. MD.

7. Paraduodenal hernias, although uncommon, have
classically been the most common type of internal
hernia. However, the incidence of postoperative
internal hernias has been increasing recently. The
two most common types, the left and right
paraduodenal hernia involve small bowel
herniating through a congenital opening in the
mesenteries. These internal hernias may result in
closed-loop bowel obstruction.
Clinical presentation
The patient typically presents with symptoms of
small bowel obstruction: abdominal pain, nausea,
vomiting.

9. Radiographic features
These hernias usually appear as a sac-like cluster of small bowel loops
in an atypical presentation. A closed-loop obstruction may occur within
these loops due to the hernia.
However, it is not unusual for small bowel loops to cluster in an atypical
position in normal patients. Thin patients may be especially challenging
since it may be difficult to follow the course of the collapsed loops of
small bowel.
Because of this, vascular landmarks around a potential internal hernia
"sac" are critical for making a confident diagnosis.
Left paraduodenal hernia
cluster of small bowel loops in the left anterior pararenal space
the cluster of small bowel loops is behind the inferior mesenteric vein
(IMV) and behind the ascending left colic artery
Right paraduodenal hernia
cluster of small bowel loops is inferior to the third portion of the duodenum
the cluster of small bowel loops is behind the superior mesenteric vein
(SMV), the superior mesenteric artery (SMA), and the right colic vein

15. Left Paraduodenal Hernia. Superior Duodenal Fossa ( pink ovoid zone). A. Axial
view. Through upper Treizt angle (red arrow). B. Coronal view. Behind Inferior
Mesenteric Vein (white arrow). Loops Herniated Position (circles).

16. Left Paraduodenal Hernia- A. Left saclike mass of herniated small bowel loops
through Landzert fossa. Mass effect on left anterior abdominal wall
(arrowhead). B. Loops situated between the stomach and pancreas.
Displacement of inferior cava vein (red arrow) and stretching and engorgement
of vessels converging to entrance and inside the hernia sac (yellow arrows).

17. Left Paraduodenal Hernia. A. Hernia sac (open arrow) located between
stomach (with arrow)and pancreatic tail (black arrow). B. MIP coronal view.
Twisting mesenteric vessels in the core of the herniated loops (red arrow).

18. Paraduodenal hernia: Contrast-enhanced CT scan of the upper abdomen shows
a saclike mass of dilated jejunal loops between the pancreatic head (P) and
stomach. The descending mesocolon (D) and stomach are displaced laterally

19. Pericecal hernias (PCHs)
In the classic literature PCHs correspond of 13% of all internal hernias. Bowel
loops, most commonly an ileal segment, herniate into the right paracolic gutter
through a congenital or acquired (most commonly by adhesions) unusual defect in
the cecal mesentery. Four different recesses in the pericecal region formed by folds
of the peritoneum have been described: superior and inferior ileocecal recess,
retrocecal recess and paracolic sulci. However, the diagnostic features
and surgical management of the four subtypes do not differ.
Clinical findings
Patients commonly report recurrent episodes of colicky intense right lower
abdominal pain. Chronic incarceration may produce symptoms compatible with
appendiceal disorders, intestinal diseases or intestinal obstruction caused by
adhesions. In PCHs however have been reported a higher incidence of occlusive
symptoms with rapid progression to strangulation and a mortality rate that can
be high as 75%.
CT findings
With CT, a cluster of fixed and dilated small bowel loops with a sac-like
appearance is noted, possibly extending into the right paracolic gutter, lateral to
the cecum and posterior to the ascending colon, which can be displaced anteriorly
or medially

21. Pericecal Hernia: Contrast-enhanced CT scan of the lower abdomen shows dilated small
bowel loops (S) and a cluster of fluid-filled small bowel loops (arrow). The ascending colon
(A) is displaced anteriorly, and ascites (arrowhead) is seen in the right paracolic gutter

22. Paracecal Hernia. A. Coronal view. Retrocecal recess (ovoid zone). B. Cadaver
simulating herniation. A,B: Loops Herniated Position (circle). Terminal Ileum (blue
arrow). Cecum (yellow arrow). Flow direction of herniated loops (curved arrows).

23. Pericecal hernia in an 83-year-old woman with a 1-day history of nausea and
right lower abdominal pain. (a) Axial contrast-enhanced CT image shows
incarcerated intestine with a saclike appearance (arrowheads) that displaces
the ascending colon (arrow) medially. (b) Oblique MPR CT image clearly shows
the hernia orifice (arrows). Laparoscopic surgery showed incarcerated
intestine in a hernia sac lateral to the ascending colon.

24. Pericecal hernia through the retrocecal recess in an 84-year-old man with colicky
right lower quadrant pain and vomiting of 48 hours duration. He underwent an
appendectomy at 54 years of age. (a) Contrast-enhanced CT scan of the mid-
abdomen shows a cluster of encapsulated small bowel loops (arrowheads) in the
lateral aspect of the right paracolic gutter and behind the ascending colon (A).
Dilated and stretched mesenteric vessels (arrow) are seen within the cluster. (b)
CT scan of the lower abdomen shows beaking and collapsed bowel loops (arrow)
at the retrocecal recess (arrowhead). The ascending colon (A) is displaced
anteriorly. Laparotomy was performed 12 hours after CT.

25. Transmesenteric (TMHs) hernias:
CT findings
Blachar et al. in 2001 have described the presence of clustered,
compressed small bowel loops in the periphery of the abdominal
cavity and the lack of omental fat between the loops and the
abdominal wall as the most useful CT signs for the detection of a
transmesenteric hernia. The herniated bowels appeared lateral to
the colon (a reversal of the normal anatomic arrangement) with
central, inferior and posterior displacement of the transverse colon
and inferior and medial displacement of the hepatic flexure. Another
study concluded that the only statistically significant CT signs
predictors of a transmesenteric hernia are clustering of small bowel
loops, especially those that are adjacent to the abdominal wall,
mesenteric vessel abnormalities including stretching, crowding and
engorgement, a displacement of the main mesenteric trunk to the
right and signs of small bowel obstruction.

27. Left Transmesenteric Hernia. Newborn 12 days old. Simple Rx (A) and
intestinal transit (B,C). Left conglomerate (circle in A,C) dilated loops of
jejunum from Treitz angle (arrow in B) due to obstruction by hernia.
Stomach (St) is also dilated. Distal loops are normal caliber (open arrow).

32. Lesser sac hernias are a type of internal hernia, where
abdominal contents protrude through the foramen of Winslow,
hence they are also known as foramen of Winslow hernia.
Epidemiology
Lesser sac hernias are rare, accounting for <0.1% of abdominal
hernias and 8% of internal hernias.
Pathology
Typically contains small bowel only (~67%) but may also contain
cecum/ascending colon and less commonly transverse colon,
gallbladder, or omentum.
Risk factors
common intestinal mesentery
intra-peritoneal right colon
long small bowel mesentery
large foramen of Winslow
elongated right liver (e.g. Riedel lobe)

33. Radiographic features
Plain radiograph
gas-filled loops of small bowel in the upper abdomen
CT
mesenteric fat/vessels posterior to portal vein, common
bile duct, hepatic artery and anterior to the inferior vena
cava
mesenteric vessels passing into the lesser sac via the
foramen of Winslow
gas and/or fluid in the lesser sac with bird beak sign
towards the foramen of Winslow
abnormal cecal position
Differential diagnosis
left paraduodenal hernia

35. Arrows showing gas contained bowel loops obstruction in foramen of winslow hernia

36. Foramen of winslow hernia: Enteroclysis shows small bowel at right hepatic flexure.

39. Foramen of Winslow Hernia. Patient without obstruction but with anomalous position of small
bowel loops (circle). They are located under the liver and upper the uncinate pancreas process
(white arrow in A) and stretching of vessels toward the herniated bowel loop (yellow arrows).

40. Lesser sac hernia through the lesser omentum in a 44-year-old man who presented with acute
abdominal pain. (a) Axial contrast-enhanced CT image shows converging mesenteric vessels and fat
(white arrows) intersecting the distal part of the stomach (black arrows) and the right gastric artery
(arrowhead). Traction and distortion of the distal part of the stomach are also seen. (b) Transparent
volume-rendered CT image shows a cluster of intestine (arrowheads) in the lesser sac, with a beak
shape (arrows) pointing toward the lesser curvature of the stomach (S). Surgery confirmed
herniated intestine in the lesser sac protruding through a defect in the lesser omentum

41. Hernia through the Broad Ligament
Hernias through a defect of the broad ligament account for only 4%–5% of
all internal hernias. The herniated viscus is the small intestine in more than
90% of cases. The typical patient with this hernia is a middle-aged woman
who has been pregnant and has no history of abdominal surgery. More
than 85% of these hernias have occurred in parous women.
Broad ligament defects are classified as congenital or acquired. Congenital
cases have an embryologic basis due to a developmental peritoneal defect
around the uterus. Acquired defects are due to surgical trauma, pregnancy
and birth trauma, perforations following vaginal manipulation, and prior
pelvic inflammatory disease. A classification for the broad ligament has
been proposed on the basis of the anatomic position of the defect: type 1 =
defect caudal to the round ligament, type 2 = defect above the round
ligament, and type 3 = defect between the round ligament and the
remainder of the broad ligament through the mesoligamentum teres.
The following are the characteristic CT appearances: (a) a cluster of dilated
small bowel loops with air-fluid levels in the pelvic cavity and (b) bowel
loops compressing the rectosigmoid dorsolaterally and the uterus ventrally

43. Broad Ligament Hernia A,B (Axial). C (Coronal). Herniated and dilated loops
posterior to uterus ( yellow arrows). Bladder (with arrow). Uterus (red arrow)

44. Broad ligament hernia in a 58-year-old woman with a 1-
day history of intermittent abdominal pain and vomiting
and a history of three normal pregnancies. (a, b) Axial
contrast-enhanced CT images obtained at different levels
show a cluster of small bowel loops in the pouch of
Douglas (arrowheads) and crowding mesenteric
vessels (arrows). The uterus (*) is deviated inferiorly and
to the right. (c) Coronal MPR CT image shows the hernia
orifice (white arrows) below the tubal and ovarian
branches (black arrow) of the left ovarian and uterine
vessels. Enlargement of the distance between the uterus
(*) and the left ovary (arrowhead) is also seen. The
patient’s abdominal pain acutely intensified, and open
surgery was performed. (d) Intraoperative photograph
(anterior view) shows incarceration of the small intestine
through a thumb-tip–sized defect (arrows) in the left
broad ligament of the uterus. Approximately 70 cm of
incarcerated intestine was infarcted and was resected,
and the broad ligament was sectioned.

45. Hernia through a defect of the right perirectal fossa in a 28-
year-old woman with continuous lower abdominal pain of 34
hours duration. (a, b) Contrast-enhanced CT scans of the pelvis
(b obtained 10 mm below a) show dilated and fluid-filled small
bowel loops (S). A cluster of dilated bowel loops (arrow) is
located to the right of the rectum (R) and behind the uterine
cervix (U). Laparotomy was performed 4 hours after CT.

46. Transomental hernias (TOHs)
Traditionally, TOHs make up 1-4% of all IHs. The term
“transomental hernia” usually refers to herniation, most
commonly of small bowel loops, cecum and sigmoid colon,
through or into a congenital or acquired abnormal defect
of the greater omentum from 2 to 10 cm in diameter
involving both leaves (four peritoneal layers) and located
in the periphery near the free edge .
CT findings
CT findings are often identical to those of a
transmesenteric hernia, however characteristic features
of TOHs are dilated bowel loops, without a sac-like
appearance, located in the most anterior portion of the
peritoneal cavity with omental vessels that run vertically
around the hernia orifice.

47. Transomental Hernia. A. Sagittal view. Great Omentum (blue zone). Hernia pathway
( curved arrow). Position of herniated loop (circle) B. Chance of herniation: Cecum
(yellow arrow). Small Bowell (pink arrow) or Sigmoid Colon (with arrow). C. Simulating
herniation of jejunal loop (curved arrow) through great omentum ( blue arrows)

48. Sigmoid mesocolon hernia: Contrast-Enhanced CT scans of the pelvis show
multiple dilated small bowel loops (S). A dilated inferior mesenteric vein (arrow)
appears as a landmark at the edge of the inferior mesentery. A saclike mass of
incarcerated jejunal loops (arrowhead) is located anterior to the left psoas muscle

49. Supravesical and pelvic (PIHs) internal hernias
CT findings:
CT findings of broad ligament hernias include a cluster of
dilated small bowel loops herniated in the pelvic cavity
laterally to the uterus with a displacement of the
rectosigmoid dorso-laterally and of the uterus ventrally
and enlargement of the distance between the uterus and
the ovary deviating in opposite directions. Furthermore
mesenteric vessels of herniated loops penetrating the
broad ligament may be seen (33, 88). In supravesical
internal hernia usually CT scans show bowel loops with a
sac-like appearance pass into the space of Retzius and lay
in front of the compressed bladder on the left or right.
These patients can present with bladder irritation and
dysuria, as the bladder is compressed by the small bowel

50. Internal supravesical hernia in a 67-year-old woman with a two-day
history of lower abdominal pain. Contrast-enhanced axial CT scan
shows intestine loops (white circle) to the left of the urinary bladder.

51. Internal supravesical hernia in a 74-year-old man with a 1-day history of right lower
abdominal pain. (a) Axial contrast-enhanced CT image shows incarcerated intestine
with a saclike appearance (arrow) that compresses the anterior wall (arrowheads) of
the urinary bladder on the right. (b) Intraoperative photograph (superoanterior view)
shows incarceration of the ileum (blue arrow) into the right supravesical fossa (green
arrows). Approximately 7 cm of intestine was infarcted and was resected. The defect
was approximately 2 cm in diameter. The hernia sac was resected, and the hernia
orifice was closed with sutures. B = urinary bladder, yellow arrow = pubis.

52. Petersen hernia in a 60-year-old woman with acute
abdominal pain and vomiting. The patient had a history
of laparoscopic distal gastrectomy and antecolic
reconstruction of a Roux-en-Y anastomosis for gastric
cancer performed 11 months earlier. (a) Axial contrast-
enhanced CT image shows a dilated biliopancreatic limb
(*) and mesenteric swirl (arrows) behind the Roux limb
(arrowhead). (b) Coronal MPR CT image shows a cluster
of intestine (★) with engorged mesenteric lymph nodes
located in the left lower quadrant, as well as a dilated
biliopancreatic limb (*). Surgery confirmed herniation of
a long segment of small intestine, including
jejunojejunostomy through a Petersen defect. Arrowhead
= Roux limb, black arrow = jejunojejunostomy, white
arrow = gastrojejunostomy.

53. Internal hernia with Whirl sign.

54. Closed loop small bowel obstruction. Contrast enhanced axial CT scan shows a
radial array of distended small bowel loops (B) with stretched and thickened
mesenteric vessels converging to a central point (white arrow). Bowel wall
thickening (arrowhead) and mesenteric edema (asterisk) can also be observed.

55. Thank You.