Small Bowel

Question 1

What is the blood supply to the duodenum?

Answer 1

Superior (GDA) and inferior (SMA) pancreaticoduodenal arteries (with anterior and posterior branches)

Question 2

Where is the primary site of absorption of B12? Bile acids? Iron? Folate?

Answer 2

B12 - terminal ileum, bile acids - terminal ileum, iron - duodenum, folate - terminal ileum

Question 3

Small bowel cell types - general function? 1. Goblet cells 2. Paneth cells, 3. Enterochromaffin cells, 4. Brunner’s glands, 5. Peyer’s patches, 6. M cells

Answer 3

1. mucin secretion 2. secretory granules, enzymes 3. APUD 5-hydroxytryptamine release, carcinoid precursor 4. alkaline solution 5. lymphoid tissue - most in ileum 6. antigen presenting cells in intestinal wall

Question 4

What are the phases of gut motility? What hormone regulates it?

Answer 4

Migrating motor complexes - phase 1 at rest, 2 acceleration and gallbladder contraction 3 peristalsis 4 deceleration – regulated by Motilin (acts on phase 3)

Question 5

Where are bile acids absorbed? What happens with bile acid malabsorption?

Answer 5

95% bile salts reabsorbed, 50% via passive absorption (non-conjugated bile slats, mostly in ileum) 50% via active absorption (conjugated bile salts in the TI by Na/K ATPase), gallstones can form after TI resection due to malabsorption of bile salts

Question 6

At what intestinal length are you at risk for short bowel syndrome? Typically caused by? What are diagnostic tests? Treatments?

Answer 6

<180 cm; need more if no ICV (in children), lose fat, B12, electrolytes, water – typically caused by one massive smallbowel resection, check sudan red stain (fecal fat), Schilling test (check for B12 absorption) - tx by slowing intestinal transit; w/ fat restriction, PPI to reduce acid/water loss, Lomotil, SB txp

Question 7

Causes of non-healing fistulas?

Answer 7

FRIENDS - foreign body, radiation, IBD, epitheliazation, neoplasm, distal obstruction, sepsis/infection

Question 8

Gallstone ileus: pathophysiology, imaging findings, treatment

Answer 8

Gallstone impacted at ICV usually, classically see air in biliary tree in pt w/ SBO, caused by fistula between GB and D2, treat bowel obstruction first - consider cholecystectomy / fistula takedown (closing duodenum) if pt is stable

Question 9

Meckel’s: pathophysiology, features, diagnosis, treatment

Answer 9

True diverticulum - caused by failure of closure of the omphalomesenteric duct, 2 ft from ICV, 2% of population, usually presents in 1st 2 years of life w/ bleeding, 2 types of tissue (pancreatic - most common, can cause diverticulitis; gastric - most symptomatic, can cause bleeding), can get Meckel’s scan (99Tc) obstruction most common presentation in adults – incidental Meckel’s usually not removed (controversial - consider in younger/children or more likelihood of symptoms), diverticulectomy or resection (esp if ulcer, need to look at controlateral bowel)

Question 10

Pathology findings of Crohn’s disease?

Answer 10

transmural involvement, segmental disease (skip lesions), cobblestoning, apthous ulcers -> narrow deep ulcers, creeping fat, fistulas, non-caveating granulomas – apthous ulcers are the first pathologic signs fo Crohn’s

Question 11

Carcinoid tumors - pathophysiology, release what hormones, what labs to order, locations, tx?

Answer 11

Serotonin produced by Kulchitsky cells (enterochromaffin cells or argentaffin cell), 5HIAA from serotonin, carcinoid syndrome caused by post-portal disease (flushing / diarrhea), localize with octreotide scan, chromogranin A highest sensitivity for detecting carcinoid, small bowel carcinoid most common, carcinoid in appendix <2 cm = appendectomy, >2 or involves base consider R hemicolectomy; chemo w/ streptozosin/5FU – increased serotonin production means less tryptophan to nicotinic acid and vitamin B3, leading to pellagra (diarrhea, dermatitis, glossitis, dementia

Question 12

Interventions to reduce post-op ileus?

Answer 12

Minimize narcotic usage with NSAIDs (ketorolac), entered (opioid receptor antagonist in GI tract) – ambulation, post-op feeding, NG tube, chewing gum have not shown to be assoc. w/ reduced ileus

Question 13

Crohn’s treatment

Answer 13

mild active disease, sulfasalazine, mesalamine; acute flares corticosteroids, more severe dz tx w/ infliximab, azathioprine, 6 mercaptopurine – 2nd line methotrexate

Question 14

What are Paneth cells?

Answer 14

Intestinal cells that secrete lysozyme, TNF, cryptidins, assist in host mucosal defense

Question 15

What are cajal cells?

Answer 15

Interstitial cell that helps regulate peristalsis (intestinal pacemaker fell), expresses KIT – cells of origin for GIST

Question 16

Duodenal diverticula - most common locations, treatment, demographic

Answer 16

most commonly in D2 near ampulla, arise on mesenteric border in areas of weakness of bowel wall where blood vessels penetrate, diverticulectomy (endoscopic, surgical) if symptomatic, do not treat incidental ones, can get bacterial overgrowth tx w/ abx, mostly in age 50-70s seen on endoscopy/imaging

Question 17

most common presentation of Meckel’s in children? why?

Answer 17

bleeding - due to heterotypic gastric mucosa causing ulcer on bowel adjacent to diverticulum

Question 18

What is a Littre hernia?

Answer 18

Incarcerated Meckel’s diverticulum hernia

Question 19

Principle fuel for the small intestine?

Answer 19

Glutamine

Question 20

Lengthening procedures for short gut syndrome?

Answer 20

STEP (serial transverse enteroplasty - snowflake cuts), Bianchi procedure (hot dog cuts)

Question 21

Indication for small bowel transplant?

Answer 21

Short gut syndrome, TPN dependent with TPN related complications, or impending/current liver failure requiring liver transplant

Question 22

Most common small bowel malignancy?

Answer 22

carcinoid (37.4%) adenocarcinoma (36.9%), lymphoma (17%)

Question 23

most common area of small bowel lymphoma? most common type? tx?

Answer 23

ileum, usually NHL, primary tx is surgical resection

Question 24

Use for Intra-arterial papaverine?

Answer 24

Splanchnic vasodilator, can be used to reverse splanchnic vasoconstriction in NOMI

Question 25

Types of acute mesenteric ischemia and their respective treatments

Answer 25

Emboli (see an occlusion just distal to SMA origin - tx w/ embolectomy vs thrombolytics), acute thrombosis (occlusion and association w/ diffuse calcifications - tx w/ surgical bypass), venous thrombosis (lack of contrast filling of either PV/SMV - heparin alone if bowel is ok) and non-occlusive mesenteric ischemia (shows diffuse spasm - supportive care, intra-arterial papaverine)

Question 26

best test to detect/monitor neuroendocrine tumor?

Answer 26

chromogranin-A

Question 27

most common cause of mechanical SBO worldwide?

Answer 27

hernia

Question 28

most common cardiac valvular lesion associated with carcinoid syndrome?

Answer 28

tricuspid insufficiency > pulm valve lesions

Question 29

most common cause of obscure GI bleeding in adults?

Answer 29

small intestine angiodysplasia&raquo_space; Crohn’s, infectious enteritis, neoplasm, vasculitis (Meckel’s in children)

Question 30

Vitamin deficiency seen in carcinoid?

Answer 30

B3 (increased serotonin production means less niacin made, can get pellagra, dermatitis, diarrhea, dementia, glossitis)

Question 31

rule of 5’s for carcinoid

Answer 31

risk of malignancy, >5 cm, >5 mitoses per 50 HPF

Question 32

What is a grynfeltt hernia?

Answer 32

hernia through superior lumbar triangle - quadratus lumborum, 12th rib, and internal oblique muscle (more common)

Question 33

What is a petit hernia?

Answer 33

hernia through inferior lumbar triangle - external oblique muscle, latissimus dorsi muscle, iliac crest

Question 34

What is a spigelian hernia?

Answer 34

through layer between rectus medially and semilunar laterally, occur below umbilicus but above epigastric vessels, no posterior rectus fascia

Question 35

What is a richter hernia?

Answer 35

hernia where only anti mesenteric border of bowel herniates through a fascial defect, involves only partial circumference of bowel, can get incarceration and strangulation without bowel obstruction

Question 36

SMA syndrome - pathophys, dx, tx

Answer 36

compression of 3rd portion of duodenum by SMA (D3), usually due to profound weight loss, decreased aortomesenteric angle, seen on CT, upper GI study, tx w/ weight gain to increase mesenteric root fat pad, operative tx is duodenojejunostomy

Question 37

Risk factors that increase damage of radiation enteritis?

Answer 37

If they received chemotherapy or has underlying vascular disease or diabetes

Question 38

Pneumatosis: causes?

Answer 38

Primary form is less common, pneumatosis cystoides intestinalis, secondary can be due to immunodeficiency, inflammatory bowel, bowel obstruction – seen with COPD, collagen vascular dz, celiac sprue, Crohn’s, steroids HIV – and ischemic bowel, NEC

Question 39

Peutz-Jegher’s syndrome: what is it, genetics, screening, prophylactic surgery?

Answer 39

autosomal dominant, mucocutaneous melanotic pigmentation and hamartomatous polyps (not adenomatous) of the small bowel (mostly jejunum/ileum), increased risk of cancer in GI tract and extraintestinal (testis, breast, uterus, ovary) – F patients begin breast/cervical ca screening at age 25

Question 40

Surgical management of lower GI bleeding due to Meckel’s?

Answer 40

segmental resection to include the diverticulum – need to find/resect area of ulceration

Question 41

Incidental Meckel’s found during laparotomy?

Answer 41

In children, resect all. In adults consider in age <50, narrow base, presence of palpable heterotopic tissue, diverticulum length >2 cm, presence of mesodiverticular band, and signs of prior diverticulitis

Question 42

what is carcinoid crisis and how do you treat it

Answer 42

pt w/ carcinoid tumor, characterized by hypotension, bronchospasm, flushing and tachycardia – tx w/ IV octreotide (50-100mcg bolus); adjunct tx w/ antihistamines

Question 43

what is blind loop syndrome? symptoms? dx? tx?

Answer 43

due to bacterial overgrowth, causes diarrhea, steatorrhea, megaloblastic anemia, weight loss, abd pain, deficient fat soluble vitamins – vitamin B12 used by bacteria causing anemia, tx w/ barium study, D-xylose test, Schilling test, tx w/ broad spectrum abx (flagyl, tetracycline, vitamin B12)