Gi -- Mesentery, Peritoneum, Omentum

Front 1

1. What are the imaging features of carcinoid tumors?
2. What is the differential diagnosis of mesenteric mass?
3. Where is the primary tumor usually found?
4. What metabolite of serotonin is helpful in making the dx?

Back 1

1.
- Mesenteric mass with coarse calcifications.
- Tethering and kinking of bowel loops
- Infiltration of small bowel mesentery 2/2 venolymphatic obstruction (look for engorged blood mesenteric veins)
- If mesenteric vessels are obstructed, this may lead to small bowel wall thickening.
2.
- Lymphoma
- Desmoid tumor
- Sclerosing mesenteritis
- Calcified hematoma.
3. Primary tumor is usually not seen on imaging but occasionally found in the distal small bowel.
4. 5-HIAA

Front 2

What are the imaging findings in sclerosing mesenteritis?

Back 2

- Typically affects the jejunal mesentery. NOTE: carcinoid tumor typically affects the ileal mesentery.
- Look for associated thin capsule and clusters of mesenteric nodes.
- May encase blood vessels resulting in venolymphatic occlusion which may lead to small bowel wall thickening.

Front 3

1. What are the imaging features of desmoid tumors (aggressive fibromatosis)?
2. Are they histologically benign or malignant? Why are they surgically resected?
3. What syndrome are desmoid tumors associated with?

Back 3

1.
- Mesenteric mass with aggressive growth
- Leads to encasement and occlusion of vessels and bowel loops.
- Desmoid tumors rarely calcify.
- Heterogeneous enhancement
2. Histologically benign but locally aggressive
3. Gardner syndrome

Front 4

What is the differential diagnosis of multiple mesenteric masses?

Back 4

1. Lymphadenopathy (neoplastic - MC lymphoma, infxn, inflammatory)
2. Desmoid tumor (aggressive abdominal fibromatosis)
3. Splenosis: Closely simulate metastases

Front 5

What is the differential diagnosis of nodular thickening of the peritoneum and omentum?

Back 5

1. Peritoneal carcinomatosis:
- Gastrointestinal and ovarian cancers are most common etiologies.
- Malignant seeding of the omentum = omental caking
2. Peritoneal mesothelioma:
- Associated with asbestos exposure (look for pleural plaques)
- Infiltrates and stiffens mesentery
3. Tuberculous Peritonitis:
- Nodular or symmetric thickening of peritoneum and mesentery
- Usually with ascites and LOW DENSITY (caseated) mesenteric nodes

Front 6

What are the imaging findings of a mesenteric hematoma?

Back 6

- Irregular mass of high density on NECT (45-65HU) at the base of the mesentery (look anterior to the pancreas).

Front 7

1. What is the cause of mesenteric adenitis?
2. What are the imaging findings in mesenteric adenitis and enteritis?
3. What patient population is affected by mesenteric adenitis?

Back 7

1. Infection of the terminal ileum (e.g., viral, Yersinia).
2. Cluster of enlarged RLQ nodes.
3. Mesenteric adenitis and enteritis usually affect children and young adults and are self-limited.

Front 8

1. What is the significance of pneumoperitoneum following trauma?
2. What is the most common site of bowel injury following blunt abdominal trauma?
3. What procedure before the CT scan can confuse the findings?
4. What are some associated findings suggesting bowel or mesenteric injury?

Back 8

1. Pneumoperitoneum following blunt trauma usually indicates bowel injury.
2. The most common sites of injury are the duodenum and proximal jejunum.
3. Preceding diagnostic peritoneal lavage may result in free intraperitoneal air and fluid.
4.
- Seatbelt hematoma of the abdominal wall
- Chance fracture

Front 9

1. What are the three most common regions for intraperitoneal seeding?
2. What effect do serosal implants have on the small bowel?
3. What tumors most commonly spread via the intraperitoneal seeding?

Back 9

1. Pouch of Douglas (most dependent position in the pelvis), ileocecal region, superior aspect of sigmoid colon.
2. Serosal implants can
- displace adjacent bowel loops
- narrow bowel lumen
- cause angulation and kinking of loops
- thicken small bowel folds,
- fold tethering
- bowel obstruction

3. Ovarian and GI tract malignancies

Front 10

1. What is the spectrum of inflammatory mesenteric processes?
2. What are the imaging findings?
3. Are calcifications common?
4. How can you differentiate retractile mesenteritis from carcinoid tumor?

Back 10

1. Mesenteric panniculitis, mesenteric lipodystrophy, sclerosing mesenteritis, or retractile mesenteritis. Fibrous evolution of mesenteric panniculitis results in retractile mesenteritis.
2.
- Mesenteric panniculitis: mesenteric soft tissue stranding without a mass.
- Sclerosing mesenteritis: misty mesentery with encapsulation and enlarged lymph nodes.
- Retractile mesenteritis: can be indistinguishable from carcinoid tumor as it can also cause tethering of bowel and obstruction. Vascular encasement and bowel ischemia can also develop.
3. Dense calcifications are common.
4. Many times they are indistinguishable. However, a large size without liver mets favors retractile mesenteritis.

Front 11

1. What is the most common primary benign mesenteric tumor?
2. Desmoid tumors are associated with what polyposis syndrome?
3. Are desmoid tumors benign or malignant?
4. Are desmoid tumors more likely to be solitary or multiple?
5. What are other benign primary mesenteric tumors?
6. What are the malignant primary mesenteric tumors?

Back 11

1. Desmoid tumor
2. Gardner syndrome
3. Desmoid tumors are benign. However, they are locally aggressive and frequently recur after surgery. Therefore, surgery is reserved for life threatening complications.
4. 75% of desmoid tumors are multiple. They can occur within the mesentery or in the abdominal wall.
5. Lipomas, GIST, hemangiomas, and neurofibromas.
6. Hemangiopericytomas, fibrosarcomas, liposarcomas, and malignant GISTs.

Front 12

What are the causes of low attenuation LAD?

Back 12

1. Treated lymphoma: generally seen when the nodes are decreasing in size and there has been a favorable response to chemotherapy.
2. Infection: Fungal (histo) or mycobacterial (TB or MAI)
3. Whipple disease: h/o malabsorption.
4. Celiac disease: gluten insensitivity
5. Necrotic mesenteric lymph nodes from mets

Front 13

1. What is cavitary mesenteric lymph node syndrome?
2. Pts with celiac disease are at increased risk of which malignancy?

Back 13

1. Represents a complication of celiac disease presenting as multiple cystic masses in the mesentery ranging in size from 2-7 cm. They contain chylous fluid surrounded by a thin rim of fibrous tissue.
2. Lymphoma

Front 14

What is the most likely dx of low attenuation LAD in a pt with HIV?

Back 14

Tuberculous infection. Less likely considerations are necrotic mets from lymphoma or Kaposi sarcoma.

Front 15

1. What is a gossypiboma?
2. What are the complications?

Back 15

1. Retained surgical sponge with abscess formation. Spongiform gas pattern centrally is a result of gas trapped in the mesh of the sponge. Look for radio-opaque filament.
2. Sinus tracts or fistula to the skin or into a hollow viscus.

Front 16

1. What is the most common location of an abscess related to spillage of gallstone during surgery?
2. How does the complication occur?

Back 16

1. Subdiaphragmatic or hepatorenal fossa.
2. Usually occurs during laproscopic cholecystectomy with spillage of stones and infected bile.

Front 17

1. What are the imaging findings in pseudomyxoma peritonei?
2. What is the most common cause of pseudomyxoma peritonei?

Back 17

1.
- Mucinous gelatinous ascites that displaces bowel loops
- Septations and calcifications
- Scalloping of the liver and splenic surface
- May thicken the peritoneum and omentum but would not cause solid masses.
2. Ruptured mucinous tumor (adenoCA), most commonly appendiceal (may simply be an appendiceal mucocele). Other causes = colon, ovary.

Front 18

What is the appearance of mesenteric lymphoma?

Back 18

- Bulky, confluent mesenteric adenopathy
- If encases mesenteric vessels = sandwich or hamburger sign.
- Treated lymphoma can be low attenuation (TB, Celiac disease, treated mets)

Front 19

1. What is the most common type of hernia? Are they more common in men or women?
2. What are the two types of inguinal hernia?
3. What is the relationship of indirect inguinal hernia to the inferior epigastric vessels?
4. What is the relationship of direct inguinal hernia to the inferior epigastric vessels?

Back 19

1. Inguinal hernia. More common in men.
2. Indirect and direct
3. The indirect inguinal hernia sac passes lateral to the inferior epigastric vessels and follows the course of the ingunial canal extending into the scrotum.
4. Direct inguinal hernia passes medial to the inferior epigastric vessels. Do not extend into scrotum.

Front 20

1. Are femoral hernias more common in men or women?
2. Where is the neck of the hernia located?
3. Is a femoral hernia more likely to get incarcerated than an inguinal hernia?
4. What is a Richter's hernia?

Back 20

1. Femoral hernias are more common in women.
2. Necks of femoral hernias are located inferior to the inguinal ligament and lateral to the pubic tubercle.
3. Yes. Femoral hernias are at increased risk of incarceration due to small neck of the hernia.
4. Entrapment of one wall of the bowel in the orifice of the hernia. Commonly found in older women with a femoral hernia. Does not cause obstruction, but it may result in ischemia of the trapped bowel wall.

Front 21

1. What is the anatomy of the obturator canal?
2. Why do pts with obturator hernia complain of medial thigh pain?
3. What is the location of the hernia sac?

Back 21

1. Obturator hernia is situated in the anterosuperior aspect of the obturator foramen. It contains the obturator artery, vein, and nerve.
2. Pts present with medial thigh pain because the hernia sac may compress the obturator nerve.
3. The hernia sac is located between the pectineus and obturator externus muscle.

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Front 22

Describe the findings of a parastomal hernia.

Back 22

Parastomal hernias are found after an ileostomy or colostomy. Small bowel loops herniate through the abdominal wall defect in a parastomal location. The bowel loops may obstruct the ileostomy.

Front 23

1. What is a Spigelian hernia?
2. What patient population is at risk for developing a Spigelian hernia?

Back 23

1. Hernia that occurs just lateral to the rectus abdominis muscle.
2. Most often results from increased intra-abdominal pressure.
- heavy laborers
- pts w/ COPD
- pts with gastric or urinary retention
- multiparous women

Front 24

1. What is the most common type of internal hernia?
2. What is more common: right or left sided paraduodenal hernia?
3. What are the imaging findings of a paraduodenal hernia?
4. What is the foramen of Winslow hernia?

Back 24

1. Paraduodenal hernia
2. Left side (75%), right side (25%).
3. Look for a mass of small bowel loops usually in the left upper quadrant, appearing to be encapsulated within a sac.
4. Protrusion of viscera into the lesser sac through the foramen of Winslow. Most commonly involves small bowel loops but may also involve the cecum or transverse colon. Look for bowel between the stomach and pancreas.

Front 25

1. What are the imaging findings of epiploic appendagitis?
2. What are the imaging findings of omental infarction?

Back 25

1.
- Oval mass of fat density seen with a thin hyperdense capsule and thrombosed internal vein.
- Surrounding fat stranding.
- Infarcted appendage typically involutes, sometimes with calcification, and may detach from the colon as a small, calcified loose body within the peritoneal cavity.
- Typically located on the left side adjacent to the sigmoid mesentery.
2.
- Heterogeneous fatty mass that is larger than epiploic appendagitis.
- Usually farther removed from the surface of the colon than for epiploic appendagitis.
- Usually right sided
- No hyperdense ring

Front 26

What are the 4 most common sites of intraperitoneal metastases?

Back 26

- Intraperitoneal metastases implant on peritoneal surfaces in regions where the ascitic flow is arrested.
- 4 common sites of intraperitoneal seeding are:
1. ILEOCECAL REGION: fluid and cells collect after cascading down the small bowel mesentery into the right lower quadrant.
2. POUCH OF DOUGLAS: most dependent and common location of intraperitoneal metastases in the abdomen.
3. Superior aspect of the sigmoid colon:
4. Right paracolic gutter: main channel for fluid traveling from the pelvis into the upper abdomen.

Front 27

Sclerosing encapsulating peritonitis (cocoon abdomen)

Back 27

Complication of continuous ambulatory peritoneal dialysis (CAPD)

SB is partially or totally entrapped in a fibrous cocoon-like sac and adhesions develop between the intestinal loops

Contributing factors: duration of peritoneal dialysis and previous episodes of bacterial or fungal peritonitis