Podcast
Questions and Answers
What are the parts of the duodenum?
What are the parts of the duodenum?
What anatomical feature distinguishes the jejunum from the ileum?
What anatomical feature distinguishes the jejunum from the ileum?
Which artery supplies blood to the jejunum and ileum?
Which artery supplies blood to the jejunum and ileum?
How is an upper GI bleed defined in relation to the Ligament of Treitz?
How is an upper GI bleed defined in relation to the Ligament of Treitz?
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What is the most common cause of small bowel obstruction (SBO)?
What is the most common cause of small bowel obstruction (SBO)?
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Which radiographic finding is suggestive of small bowel obstruction?
Which radiographic finding is suggestive of small bowel obstruction?
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What distinguishes colonic haustra from valvulae conniventes?
What distinguishes colonic haustra from valvulae conniventes?
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What is a characteristic finding in plain radiographs of small bowel obstruction?
What is a characteristic finding in plain radiographs of small bowel obstruction?
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What is the most common cause of small bowel obstruction (SBO)?
What is the most common cause of small bowel obstruction (SBO)?
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How are adhesions typically visualized in imaging?
How are adhesions typically visualized in imaging?
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What does strangulation refer to in the context of hernias?
What does strangulation refer to in the context of hernias?
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Which type of inguinal hernia is most common and more prevalent in males?
Which type of inguinal hernia is most common and more prevalent in males?
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In a direct inguinal hernia, where is the neck of the hernia located relative to the inferior epigastric vessels?
In a direct inguinal hernia, where is the neck of the hernia located relative to the inferior epigastric vessels?
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Which condition would qualify as incarceration in hernias?
Which condition would qualify as incarceration in hernias?
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What is an Amyand hernia?
What is an Amyand hernia?
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What condition is typically associated with direct inguinal hernias?
What condition is typically associated with direct inguinal hernias?
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What is a characteristic feature of a femoral hernia compared to an inguinal hernia?
What is a characteristic feature of a femoral hernia compared to an inguinal hernia?
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Which hernia is associated with ipsilateral cryptorchidism in male infants?
Which hernia is associated with ipsilateral cryptorchidism in male infants?
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Which statement about Richter hernia is true?
Which statement about Richter hernia is true?
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In an internal hernia, what is a common risk associated with it?
In an internal hernia, what is a common risk associated with it?
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What is the most common type of transmesenteric hernia?
What is the most common type of transmesenteric hernia?
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Which hernia type is primarily seen following Roux-en-Y gastric bypass?
Which hernia type is primarily seen following Roux-en-Y gastric bypass?
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What is a common characteristic of paraduodenal hernias?
What is a common characteristic of paraduodenal hernias?
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What imaging sign may be visible if volvulus is present in an internal hernia?
What imaging sign may be visible if volvulus is present in an internal hernia?
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Which imaging modality has become the preferred choice for evaluating Crohn's disease compared to endoscopy and barium fluoroscopy?
Which imaging modality has become the preferred choice for evaluating Crohn's disease compared to endoscopy and barium fluoroscopy?
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What is the most common CT manifestation of enteritis?
What is the most common CT manifestation of enteritis?
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What characterizes the bowel involvement in Crohn's disease?
What characterizes the bowel involvement in Crohn's disease?
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Which of the following is NOT considered penetrating disease in the context of Crohn's disease?
Which of the following is NOT considered penetrating disease in the context of Crohn's disease?
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What is one of the earliest histologic changes seen in Crohn's disease?
What is one of the earliest histologic changes seen in Crohn's disease?
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Which feature is typical of stricturing disease in Crohn's disease?
Which feature is typical of stricturing disease in Crohn's disease?
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What is a disadvantage of CT and MRI when compared to traditional fluoroscopy and endoscopy?
What is a disadvantage of CT and MRI when compared to traditional fluoroscopy and endoscopy?
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Which of the following is considered as a part of penetrating disease in Crohn's disease?
Which of the following is considered as a part of penetrating disease in Crohn's disease?
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What is the most characteristic imaging finding in celiac disease?
What is the most characteristic imaging finding in celiac disease?
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What is the primary mechanism underlying celiac disease?
What is the primary mechanism underlying celiac disease?
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Which imaging technique is mentioned as showing flocculations of barium in celiac disease?
Which imaging technique is mentioned as showing flocculations of barium in celiac disease?
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What appearance does the jejunum have in celiac disease due to villous atrophy?
What appearance does the jejunum have in celiac disease due to villous atrophy?
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Which of the following is less common in celiac disease compared to other causes of enteritis?
Which of the following is less common in celiac disease compared to other causes of enteritis?
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What occurs to the jejunal folds in celiac disease?
What occurs to the jejunal folds in celiac disease?
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What condition may result from Crohn's disease as demonstrated in imaging?
What condition may result from Crohn's disease as demonstrated in imaging?
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Which feature is generally associated with CT findings in celiac disease?
Which feature is generally associated with CT findings in celiac disease?
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Study Notes
Anatomy of the Small Bowel
- The duodenum has 4 parts: superior, descending, horizontal, and ascending.
- Valvulae conniventes (folds in the bowel wall) are circumferential in the small bowel, but not in the colon.
- The SMA supplies blood to the jejunum and ileum.
- The duodenum receives blood from branches of the celiac axis.
- The jejunum has larger, closer folds and villi compared to the ileum.
- The Ligament of Treitz separates the upper and lower GI tracts.
- The Ligament of Treitz is not visualized directly on imaging, but can be indirectly found at the edge of the ascending duodenum.
- An upper GI bleed occurs proximal, and a lower GI bleed occurs distal, to the Ligament of Treitz.
Small Bowel Obstruction
- SBO is most commonly caused by adhesions from prior surgery or hernia.
- SBO can also be caused by neoplasm, stricture, or intussusception, but these are less common.
- On abdominal x-ray, SBO shows small bowel distention greater than 3 cm.
- Multiple air-fluid levels at different heights may be seen on upright abdominal x-ray.
- Lack of gas in the colon is suggestive of SBO.
- Post-operative ileus (recent surgery, gas may be seen in colon) and focal ileus (inflammation, dilatation near inflammation) are key differentials for SBO.
- Adhesions are an imaging diagnosis of exclusion.
- If no other cause for obstruction (mass or hernia), SBO is likely due to adhesions.
- Most patients with SBO due to adhesions have had prior abdominal surgery.
- Non-operative management of SBO due to adhesions includes nasogastric tube decompression and bowel rest.
- External hernias are the second most common cause of SBO.
- 75% of external hernias occur in the groin.
- Strangulation refers to ischemia due to vascular compromise of the hernia.
- Incarceration refers to a hernia that cannot be reduced, but is not an imaging finding.
- Indirect inguinal hernias are the most common and are more common in males.
- The neck of the hernia is located lateral to the inferior epigastric vessels.
- Indirect inguinal hernias are considered congenital due to a patent processus vaginalis.
- Direct inguinal hernia necks are medial to the inferior epigastric vessels and protrude through a weak area in the anterior abdominal wall.
- Direct inguinal hernias are considered acquired and may be caused by increased intra-abdominal pressure.
- An inguinal hernia with the appendix is called an Amyand hernia.
- A Meckel’s diverticulum within a hernia is called a Littre hernia.
- A femoral hernia can compress the femoral vein.
- A Spigelian hernia is a lateral ventral hernia between the rectus abdominis and lateral oblique muscles.
- A Richter hernia occurs when only the antimesenteric portion of the bowel wall is herniated, and is more likely to result in strangulation than obstruction.
- An internal hernia is a protrusion of bowel through a defect or opening in the peritoneum or mesentery.
- Internal hernias have a high rate of volvulus, which may show as the "whirl sign".
- Common internal hernia subtypes include transmesenteric, paraduodenal, and foramen of Winslow.
- A transmesenteric hernia is a bowel herniation through a defect in any of the three true mesenteries (small bowel, transverse mesocolon, and sigmoid mesentery).
- The most common type of transmesenteric hernia is the transmesocolic hernia.
- Transmesocolic hernias are seen most commonly post Roux-en-Y gastric bypass or biliary-enteric anastomosis from liver transplant.
- Paraduodenal hernias are congenital, due to embryologic failure of mesenteric fusion and resultant mesenteric defect.
- Paraduodenal hernias are more common on the left side and are associated with abnormal intestinal rotation.
Enteritis and IBD
- Enteritis is inflammation of the small bowel, and is most commonly shown on CT as bowel wall thickening.
- Mesenteric stranding or free fluid may also be present in enteritis.
- Crohn's disease can affect any part of the GI tract, but most commonly involves the terminal ileum.
- Crohn's disease presents discontinuously, with characteristic "skip lesions" between normal GI tract.
- Crohn's disease can have three phenotypes: active inflammation, stricturing disease, and penetrating disease.
- Crohn's disease shows mural hyperenhancement, intramural edema, and mural ulcerations on CT.
- Stricturing disease shows luminal narrowing with upstream dilatation.
- Penetrating disease shows sinus tracts, simple fistulas, complex fistulas, inflammatory mass, and abscess.
- Perianal disease is not considered penetrating disease in Crohn's disease.
- Endoscopy, barium fluoroscopy (small bowel follow-through, enteroclysis, barium enema), CT, and MR enterography are used to evaluate Crohn's disease.
- CT and MRI allow for full bowel wall evaluation, extraintestinal complications, and vascularity.
- CT and MRI have limitations for spatial resolution and sensitivity for detecting subtle early signs of disease.
- Celiac disease (sprue, gluten-sensitive enteropathy) is an autoimmune, proximal enteritis due to a t-cell mediated immune response to gluten.
- The primary sites of involvement in celiac disease are the duodenum and jejunum.
- The most characteristic imaging finding of celiac disease is reversal of jejunal and ileal fold patterns.
- In celiac disease, the loss of jejunal folds due to villous atrophy causes a compensatory increase in the number of ileal folds.
- A small bowel follow-through may show flocculations of barium due to villous atrophy.
- The "moulage" (casting) effect refers to a cast-like appearance of the jejunum.
- CT findings in celiac disease include dilated, fluid-filled bowel loops, with potential enteric contrast flocculations.
- Reversal of jejunal and ileal fold patterns can be seen on CT in celiac disease.
- Contrast can be seen centrally and peripherally on CT in celiac disease.
- Other CT findings of celiac disease include mesenteric adenopathy and mesenteric vessel engorgement.
- Diffuse bowel wall thickening and ascites are less common in celiac disease compared to other causes of enteritis.
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Description
This quiz covers the anatomy of the small bowel, detailing the specific parts of the duodenum and blood supply to the jejunum and ileum. Additionally, it explores small bowel obstruction (SBO), its common causes, and diagnostic features observed on abdominal x-ray.
