Presentation1, radiological imaging of internal abdominal hernia.

Health& Medicine

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

2. 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.

3. 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

4. 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).

5. 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).

6. 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).

7. 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

8. 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

9. 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

10.   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).

11. 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.

12. 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.

13. 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.

14. 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).

15. 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)

16. 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

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

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

19. 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).

20. 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

21. 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

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

23. 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.

24. 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.

25. 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.

26. 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)

27. 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

28. 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

29. 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 .

30. 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.

31. 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.

32. Internal hernia with Whirl sign.

33. 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.

34. Thank You.