Small bowel

Question 1

What is the retroperitoneal portion of the small bowel?

Answer 1

2nd-4th duodenum

Question 2

Where is iron and calcium absorbed in the small bowel?

Answer 2

Duodenum

(proximal jejunum also absorbs calcium)

(ileum: vitamin B12, folate, conjugated bilirubin)

Question 3

What are the characteristics of the jejunum?

Answer 3

Long vasa recta
Circular mucosal folds
95% of all NaCl and water absorbed in jejunum
Maximum site of all absorption except b12, folate, calcium, iron

95% of all NaCl and water absorbed in jejunum. Maximum site of all absorption except B12, folate, calcium, and iron.

Question 4

What aids in iron absorption?

Answer 4

Vitamin C

Question 5

What are the characteristics of the ileum?

Answer 5

Short vasa recta and flat villi

Question 6

What are Paneth cells?

Answer 6

Host defense cells in the small bowel.

Question 7

What do enterochromaffin cells release?

Answer 7

Enterochromaffin cells - carcinoid precursor. Releases serotonin

Question 8

What do Brunner’s glands secrete?

Answer 8

Alkaline solution in the duodenum.

Question 9

What are Peyer’s patches?

Answer 9

Part of Mucosa-associated lymphoid tissues (MALT), high in ileum, and secrete IgA.

Question 10

What are M cells?

Answer 10

Antigen presenting cells on the wall of the small bowel.

Question 11

What is the most common cause of small bowel obstruction (SBO)?

Answer 11

1 Adhesions, #2 Hernia, #3 Cancer

Question 12

What is the most common cause of large BO?

Answer 12

MCC of large BO with or without surgery = CANCER

Question 13

What are concerning signs that a patient with SBO may require an operation?

Answer 13

Signs concerning that patient may require an operation: #1 = free fluid, mesenteric edema, obstipation > 12 hours, presence of 2 or more beak signs (tapering of bowel)
If above is absent: recent trials show giving them a gastrograffin challenge early is therapeutic and diagnostic

Question 14

What is the Crypts of Lieberkuhn responsible for?

Answer 14

Crypts of Lieberkuhn – secrete carbohydrate processing enzyme. Basal portion has multipotent cells

Question 15

What phases are involved in the migrating motor complex?

Answer 15

Phase I - rest, Phase II - acceleration and gallbladder contraction, Phase III - peristalsis, Phase IV - deceleration

Question 16

What hormone is most important in the migrating motor complex?

Answer 16

Motilin (Release during non-eating, digestive phase) is the most important hormone in migrating motor complex acts on phase III

Question 17

What are the consequences of steatorrhea?

Answer 17

Poor nutrition, fat-soluble vitamin deficiency, and deficiency of essential fatty acids (wound healing)

Question 18

What causes steatorrhea?

Answer 18

Gastric acid: decreases pH -> increases intestine motility -> poor fat absorption (e.g. short gut syndrome)

Pancreatic enzyme deficiency: e.g. chronic pancreatitis

Bile salt deficiency (terminal ileum resection, biliary obstruction) -> interferes with micelle formation and fat absorption

Question 19

What type of diverticulum is most common in the small bowel?

Answer 19

False diverticulum
90% asymptomatic
MC in Duodenum
MC 2nd portion
If asymptomatic Observe unless perforated, bleeding, causing obstruction
Can have bacterial overgrowth – N/V, malabsorption, steatorrhea, b12 deficiency  Tx: Tetracycline and flagyl

Duodenal:
- Can cause hemorrhage, pancreatitis, biliary obstruction (cholangitis), perforation, diverticulitis
- Only ones in 2nd portion near ampulla cause cholangitis or pancreatitis
- Dx: EGD or ERCP (BEST)
- Tx:
- For bleeding or perforation  diverticulectomy
- for biliopancreatic (cholangitis/pancreatitis) symptoms ERCP with sphincterotomy +/- stent
- Avoid whipple here

Jejunal ileal
- Diverticulitis: non-op initially
- Tx: any symptoms: segmental resection

Question 20

What is the most common tumor of the small bowel?

Answer 20

Neuroendocrine tumors are the MC SB tumor.  #1Carcinoid is the MC small bowel malignancy, then adenocarcinoma, then lymphoma
Small bowel NET have very high chance of mets, 50%
Neuroendocrine tumors of small bowel
- Duodenal < 1 cm  endoscopic resection
- Duodenal 1-2 cm 
- Duodenal > 2 cm  formal resection, whipple if in 2nd portion
- Rest of small bowel  formal resection

Question 21

What is the prognosis for small bowel adenocarcinoma?

Answer 21

2 mc sb CA

MC in the 2nd portion of duodenum (periampullary)
RF: Cystic fibrosis, celiac disease, Crohn’s disease, FAP, HNPCC, Peutz’s Jegers,
All patients with SB adenocarcinoma need genetic testing
Worse prognosis if: <10 LN retrieved, location in ileum, + nodes
Sx: Obstruction and jaundice
Tx: Resection with adenectomy. Whipple if 1st or 2nd portion
3rd and 4th portion of duo -> duodenojejunostomy

Question 22

What should be done for leiomyoma of the small bowel?

Answer 22

All need to be resected due to difficulty differentiating from leiomyosarcoma.

Question 23

What is the treatment for leiomyosarcoma of the small bowel?

Answer 23

Usually in jejunum and ileum
Most are extraluminal
Make sure it’s not GIST, check C-kit
Tx: resection without lymphadenectomy

Question 24

Small bowel adenomas

Answer 24

MC in duodenum
Pre-malignant
need endoscopic resection

Question 25

Ampullary villous adenoma

Answer 25

– Pre-malignant
- Sx: Obstructive jaundice and heme positive stools (classic)
- Dx: ERCP with Bx – Has a high false negative rate: Up to 70% of these have CA
- Will see soap bubble or paint brush appearance on contrast studies = pathognomonic
- Tx: endoscopic or wide local excision
- If benign: after resection will likely need sphincteroplasty
- Send for frozen to confirm benign, if malignant= Whipple
- No whipple if benign

Duodenal adenomas= increased risk of colon and rectal cancers-> need screening