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1

intestine: nutrient and water absorption

small intestine

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intestine: water absorption

large intestine

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portions of the duodenum

- bulb (1st portion) - 90% of ulcers here
- descending (2nd) - contains ampulla of Vater (duct of wirsung) and duct of santorini
- transverse (3rd)
- ascending (4th)

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portions of the duodenum that are retroperitoneal

descending and transverse portions

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transition point of the 3rd and 4th portions of the duodenum

acute angle between the aorta (posterior) and SMA (anterior)

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vascular supply duodenum

superior (off gastroduodenal artery) and inferior (off SMA) pancreaticoduodenal arteries
- both have anterior and posterior branches
- many communications between these arteries

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100 cm long; long vasa recta, circular muscle folds
- absorbs 95% NaCl and 90% water
- vascular supply: SMA

Jejunum

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maximum site of all absorption except for b12 (terminal ileum), bile acids (ileum - non conjugated; terminal ileum - conjugated), iron (duodenum) and folate (terminal ileum)

jejunum

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150 cm long, short vasa recta, flat
- vascular supply: sma

ileum

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what is absorbed at the intestinal brush border?

maltase, sucrase, limit dextrinase, lactase

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normal sizes: small bowel / transverse colon / cecum

3 / 6 / 9 cm

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SMA eventually branches into the...

ileocolic artery

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cell types of the small intestine

absorptive cells, goblet cells (mucin secretion), paneth cells (secretory granules, enzymes), enterochromaffin cells, runner's glands, peyer's patches, m cells

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What do goblet cells secrete?

mucin secretion

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What do paneth cells secrete?

secretory granules, enzymes

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What do enterochromaffin cells secrete?

APUD, 5-hydroxytryptamine release, carcinoid precursor

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What do brunner's cells secrete?

alkaline solution

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What do M cells secrete?

antigen-presenting cells in intestinal wall

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released into the gut; also in mother's milk

IgA

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small bowel has both heme and Fe transporters

Fe

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where is iron absorbed?

duodenum

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where is folate absorbed?

terminal ileum

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where is b12 absorbed?

terminal ileum

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where are bile acids absorbed?

- ileum: non conjugated
- terminal ileum: conjugated

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what are the phases of migrating motor complex (gut motility)?

phase 1: rest
2: acceleration and gallbladder contraction
3: peristalsis
4: deceleration

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Most important hormone in migrating motor complex (Acts on phase 3)

motilin

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percent of bile salts reabsorbed

95%

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how are bile salts reabsorbed?

- 50% passive absorption (non-conjguated bile salts) - 45% ileum, 5%
- 50% active resorption (conjugated bile salts) in terminal ileum (Na/K ATPase); conjugated bile salts are absorbed only in the terminal ileum

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When do gallstones form?

gallstones form after terminal ileum resection from malabsorption of bile salts

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how is diagnosis of short-gut syndrome made?

symptoms; not length of bowel

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diarrhea, steatorrhea, weight loss, nutritional deficiency
- lose fat, B12, electrolytes, water

short-gut syndrome

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stains: checks for fecal fat

sudan red stain

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test: checks for b12 absorption (radiolabeled b12 in urine)

schilling test

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how much bowel do you need to survive off TPN?

75 cm to survive off TPN; 50 cm with competent ileocecal valve

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Tx: short gut syndrome

restrict fat, ppi to reduce acid, lomotil (diphenoxylate and atropine)

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causes of steatorrhea

- gastric hyper secretion of acid
- interruption of bile salt resorption

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how does gastric hyper secretion of acid cause steatorrhea?

decreased pH-> increased intestinal motility; interferes with fat absorption

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how does interruption of bile salt resorption cause steatorrhea?

(eg terminal ileum resection) interferes with micelle formation and fat absorption

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Tx: steatorrhea

control diarrhea (lomotil); decrease oral intake, especially fats, pancreas, ppi

40

causes of non healing fistulas

FRIENDS: fistulas, radiation, inflammatory bowel disease, epithelialization, neoplasm, distal obstruction, sepsis/infection

41

characteristics of high-output fistulas

- more likely with proximal bowel (duodenum or proximal jejunum)
- less likely to close with conservative management

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colonic fistulas vs small bowel
- which are more likely to close?

colonic fistulas are more likely to close than those in small bowel

43

nonhealing fistula: patients with persistent fever

need to check for abscess (fistulogram, abdominal CT, upper GI with small bowel follow through)

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treatment: fistulas

most fistulas are iatrogenic and treated conservatively first: NPO, TPN, skin protection (stoma appliance), octreotide

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how do most non healing fistulas close?

majority close spontaneously without surgery

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surgical options of non healing fistulas

resect bowel segment containing fistula and perform primary anastomosis

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MCC obstruction without previous surgery

Small bowel: hernia
Large bowel: cancer

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MCC obstruction with previous surgery

Small bowel: adhesions
Large bowel: cancer

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-pain: intermittent, intense, colicky; often relieved with vomiting
- vomiting: large volumes, bilious, frequent
-tenderness: epigastric or periumbilical; quite mild unless strangulated
- distention: absent
- obstipation: may not be present

proximal small bowel obstruction (open loop)

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- pain: intermittent to constant
- vomiting: low volume and frequency; progressively feculent with time
- tenderness: diffuse and progressive
- distention: moderate to marked
- obstipation: present

Distal small bowel obstruction (open loop)

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- pain: progressive, intermittent constant; rapidly worsens
- vomiting: may be prominent (reflex)
- tenderness: diffuse, progressive
- distention: often absent
- obstipation: may not be present

small bowel obstruction (closed loop)

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- pain: continuous
- vomiting: intermittent, not prominent; feculent when present
- tenderness: diffuse
- distention: marked
- obstipation: present

colon and rectum obstruction

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type of bowel obstruction with no distention

proximal small bowel (open loop)

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AXR: obstruction

air-fluid level, distended loops of small bowel, distal decompression

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tx: 3rd spacing of fluid into bowel lumen with obstruction

need aggressive fluid resuscitaiton

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why is there air with bowel obstruction?

from swallowed nitrogen

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tx: bowel obstruction

bowel rest, NGT, IVF, -> cures 80% of partial SBO, 40% of complete SBO

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obstruction: surgical indications

progressing pain, peritoneal signs, fever, increasing WBCs (all signs of strangulation or perforation), or failure to resolve

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small bowel obstruction from gallstone usually in the terminal ileum

gallstone ileus

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imaging: what do you see in gallstone ileus?

classically see air in the biliary tree in a patient with small bowel obstruction

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what causes gallstone ileus?

caused by a fistula between the gallbladder and second portion of duodenum

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tx: gallstone ileus

remove stone from terminal ileum
- can leave gallbladder and fistula if patient too sick
- if not too sick, perform cholecystectomy and close duodenum

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2 ft from ileocecal valve
2% of population
usually presents in 1st 2 years of life with bleeding; is a true diverticulum
- accounts for 50% of all painless lower GI bleeds in children

meckel's diverticulum

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what causes meckel's diverticulum?

caused by failure of closure of the omphalomesenteric duct

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most common tissue found in meckel's (can cause diverticulitis)

pancreas tissue

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most likely to be symptomatic (bleeding most common) - tissue in meckel's diverticulum

gastric mucosa

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two types of tissue in meckel's diverticulum

pancreatic and gastric tissue

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adults: MC presentation of meckel's diverticulum

obstruction

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when do you remove meckel's diverticulum?

incidental -> usually not removed unless gastric mucosa suspected (diverticulum feels thick) or has a very narrow neck

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dx: meckel's diverticulum

can get a meckel's scan (99Tc) if having trouble localizing (mucosa lights up)

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Tx: meckel's diverticulum

diverticulotomy for uncomplicated diverticulitis or bleeding
- Need segmental resection for complicated diverticulitis (e.g. perforation), neck has > 1/3 the diameter of the normal bowel lumen, or if diverticulitis involves the base

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what do you need to rule out in duodenal diverticula?

gallbladder-duodenal fistula

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primary management: duodenal diverticula

observation unless perforated, bleeding, causing obstruction, or highly symptomatic

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Frequency of duodenal diverticula

Duodenal > jejunal > ileal

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Tx: duodenal diverticula

Segmental resection if symptomatic.
- if juxta-ampullary usually can't get resection and need choledochojejunostomy for biliary or ERCP with stent for pancreatitis symptoms (Avoid Whipple here)

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inflammatory bowel disease causing intermittent abdominal pain, diarrhea and weight loss; can also cause bowel obstructions and fistulas.
- 15-35 years old at 1st presentation; in Ashkenazi Jews

Crohn's Disease

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portion of alimentary where crohn's occurs

can occur anywhere from mouth to anus; usually spares rectum

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extraintestinal manifestations of crohn's

arthritis, arthralgias, pyoderma gangrenosum, erythema nodosum, ocular diseases, growth failure, megaloblastic anemia from folate and vitamin b12 malabsorption.

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crohn's: most commonly involved bowel segment

terminal ileum

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crohn's: 1st presentation in 5%

anal / perianal disease
- Tx: flagyl
- anal disease most common symptom: large skin tags

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crohn's disease: most common sites for initial presentation

- terminal ileum and cecum: 40%
- colon only: 35%
- small bowel only: 20%
- perianal: 5%

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Dx: crohn's disease

colonoscopy with biopsies and enteroclysis can help make the diagnosis

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pathology: crohn's disease

transmural involvement, segmental disease (skip lesions), cobblestoning, narrow deep ulcers, creeping fat, fistulas

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medical treatment: crohn's

5-ASA and loperamide for maintenance; steroids for acute flares
- remicade (infliximab; TNF-alpha inhibitor) - for fistulas or steroid-resistant disease

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crohn's: agents affecting natural course of disease

no agents affect natural course of disease

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may induce remission and fistula closure with small bowel crohn's disease

TPN

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percent of patient needing operation in crohn's

90%

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surgical indications: crohn's disease

obstruction
abscess
megacolon
hemorrhage
blind loop obstruction
fissures
fistulas: enterocutnaeous, perineal, anarectovaginal

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margins in crohn's surgery

do not need clear margins; just get 2cm away from gross disease with surgery

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obstruction: crohn's

often partial and can be initially treated conservatively

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abscess: crohn's

usually treated with percutaneous drainage

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megacolon: crohn's

perforations occurs in 15%; usually contained

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hemorrhage: crohn's

unusual in crohn's but can occur

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blind loop obstruction: crohn's

need resection

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fissures: crohn's

no lateral internal sphincteroplasty in patients with crohn's disease

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enterocutaneous fistula: crohn's

can usually be treated conservatively

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perineal fistula: crohn's

unroof and rule out abscess; let heal on its own

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anorectovaginal fistula: crohn's

may need rectal advancement flap; possible colostomy

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chron's: management of patients with diffuse disease of colon

proctocolectomy and ileostomy the procedures of choice (no pouches or ilio-anal anastomosis with crohn's)

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tx: incidental finding of IBD in patient with presumed appendicitis who has normal appendix

remove appendix is cecum not involved (avoids future confounding diagnosis)

101

crohn's:
- consider if patient has multiple bowel strictures to save bowel length
- probably not good for patient's 1st operation as it leaves disease behind

stricturoplasty (longitudinal incision through stricture, close transversely)

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complications of stricturoplasty

10% leakage/abscess/fistula rate with stricturoplasty (all of which can usually be treated conservatively)

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recurrence rate requiring surgery for Crohn's disease after resection

50% recurrence rate

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chron's: complications from removal of terminal ileum

- decreased b12 uptake can result in megaloblastic anemia
- decreased bile salt uptake causes osmotic diarrhea (bile salts) and steatorrhea (fat) in colon
- decreased oxalate binding (calcium oxalate kidney stones - hyperoxaluria)
- gallstones

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chron's: mechanisms of megaloblastic anemia

decreased b12 uptake

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crohn's: mechanism of osmotic diarrhea and steatorrhea

decreased bile salt uptake

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crohn's: mechanism of hyperoxaluria (calcium oxalate kidney stones)

decreased oxalate binding to calcium secondary to increased intraluminal fat (fat binds Ca) -> oxalate then gets absorbed in the colon -> released in urine -> calcium oxalate kidney stones

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crohns: mechanism of gallstones

can form after terminal ileum resection from malabsorption of bile salts

109

what produces serotonin in carcinoid?

kulchitsky cells (enterochromaffin cell or argentaffin cell)

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what is serotonin (carcinoid) a part of?

part of amine precursor uptake decarboxylase system (APUD)

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breakdown product of serotonin - can measure this in urine

5-hiaa

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what does carcinoid tumor release?

serotonin
bradykinin

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carcinoid: caused by bulky liver metastases

carcinoid syndrome (intermittent flushing - kallikrein ; diarrhea - serotonin)

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hallmark symptoms of carcinoid syndrome

intermittent flushing (kallikrein)
diarrhea (Serotonin)

- can also get asthma-type symptoms (bradykinin) and right heart valve lesions

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what do you think about: if patient has carcinoid syndrome with small bowel carcinoid primary

it indicates metastasis to liver (liver usually clears serotonin)

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carcinoid syndrome: what do you do if you perform resection of liver metastases

perform cholecystectomy in case of future embolization

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carcinoid: best for localizing tumor not seen on ct scan

octreotide

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highest sensitivity for detecting a carcinoid tumor

chromogranin a level

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most common site for carcinoid tumor (50% of carcinoids arise here)

appendix carcinoid (ileum and rectum next most common)

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carcinoid: site where patients are at increased risk for multiple primaries and second unrelated malignancies

small bowel carcinoid

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tx: carcinoid in appendix
- 2cm or involving base

- 2 cm or involving base: right hemicolectomy

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tx: carcinoid anywhere else in GI tract aside from appendix

treat like cancer (segmental resection with lymphadenectomy)

123

chemotherapy for carcinoid

streptozocin and 5FU; usually just for unresectable disease

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useful for carcinoid syndrome palliation

octreotide

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carcinoid: tx for bronchospasm

aprotinin

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carcinoid: tx for flushing

alpha blockers (phenothiazine)

127

what can cause false elevations in 5-hiaa?

fruits

128

same colon CA risk as ulcerative colitis

crohn's pancolitis

129

- can occur from small bowel or cecal tumors
- most common presentation is obstruction
- worrisome in adults as it often has a malignant lead point (i.e. cecal CA)

tx: resection

intussusception in adults

130

- most found in duodenum; present with bleeding, obstruction
- need resection when identified (often done with endoscope)

Adenomas - benign small bowel tumors

131

- autosomal dominant
- hamartomas throughout GI tract (small and large bowel)
- mucocutaneous melanotic skin pigmentation
- pts have increased extra intestinal malignancies (mc- breast CA) and a small risk of GI malignancies
- no prophylactic colectomy

Peutz-Jeghers syndrome

132

mc extraintestinal malignancy in peutz-jeghers syndrome

breast cancer

133

most common malignant small bowel tumor

adenocarcinoma (rare)

134

where are most small bowel adenocarcinomas found?

high proportion are in the duodenum

135

Symptoms of adenocarcinoma small bowel

obstruction, jaundice

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tx: small bowel adenocarcinoma

resection and adenectomy; Whipple if in 2nd portion of duodenum

137

duodenal CA risk factors

FAP, Gardner's, poylps, adenomas, von Recklinghausen's

138

- usually in jejunum and ileum; most extraluminal
- hard to differentiate compared with leiomyoma (>5 mitoses/HPF, atypia, necrosis)

leiomyosarcoma

139

what do you need to rule out in leiomyosarcoma?

make sure it is not a GIST (check for c-kit)

140

tx: leiomyosarcoma in small bowel

resection; no adenectomy required

141

- usually in ileum; associated with Wegener's, SLE, AIDS, Crohn's, celiac sprue
- usually NHL B cell type
- Post transplantation: increased risk of bleeding and perforation

Lymphoma - malignant small bowel tumor

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dx: lymphoma - malignant small bowel

abdominal ct, node sampling

143

tx: lymphoma - small bowel

malignancy: wide en block resection (include nodes) unless 1st or 2nd portion of the duodenum (chemo-XRT, no Whipple)

144

survival rate small bowel lymphoma

40% 5 year survival rate

145

highest incidence with colostomies; generally well tolerated and do not need repair unless symptomatic

parastomal hernias

146

most common stomal infection

candida

147

(hartmann's pouch) - secondary to lack of short-chain fatty acids
- tx: short-chain fatty acids enemas

diversion colitis

148

most common cause of stenosis of stoma
- tx: dilation if mild

ischemia

149

most common cause of fistula near stoma site

crohn's disease

150

underneath stoma stie, often caused by irrigation device

abscesses

151

increased in patients with ileostomy

gallstones and uric acid kidney stones

152

1) anorexia
2) abdominal pain (periumbilical)
3) vomiting
- pain gradually migrates to the RLQ as peritonitis sets in
- most commonly occurs in patients 20-35 years
- patients can have normal WBC count

Appendicitis

153

CT scan in appendicitis:

diameter > 7mm
wall thickness > 2mm (looks like a bull's eye)
fat stranding
no contrast in appendiceal lumen
try to give rectal contrast

154

where is the appendix most likely to perforate?

midpoint of anti-mesenteric border

155

mcc appendicitis in children; can follow a viral illness

hyperplasia

156

mcc appendicitis in adults

fecalith

157

what is the sequence of events in appendiceal luminal obstruction?

luminal obstruction is followed by distention of the appendix, venous congestion and thrombosis, ischemia, gangrene necrosis, and finally rupture

158

appendicitis: nonoperative situtation

CT scan shows wall-offed perforated appendix (usually in elderly)
- TX: pecutaneous drainage and interval appendectomy at later date as long as symptoms are improving.

159

follow up: nonoperative appendicitis (walled-off perforated appendix)

consider follow-up barium enema or colonoscopy to rule out perforated cecal colon CA

160

why do children and elderly have higher propensity for appendices rupture?

secondary to delayed diagnosis

161

children often have higher fever and more vomiting and diarrhea

appendicitis

162

elderly: signs and symptoms can be minimal; may need right hemicolectomy if cancer suspected

appendicitis

163

frequency of appendicitis in infants

appendicitis is infrequent in infants

164

appendicitis: patient generally more ill; can have evidence of sepsis

peforaiton

165

mcc of acute abdominal pain in the first trimester

appendicitis

166

when is appendicitis likely to occur in pregnancy?

more likely to occur in the 2nd trimester but is not the most common cause of abdominal pain

167

when in appendicitis more likely to perforate in pregnancy?

more likely to perforate in the third trimester - confused with contractions

168

where do you make the appendectomy incision in pregnancy?

need to make incision where the patient is having pain - the appendix is displaced superiorly (cephalad)

169

appendicitis: possible symptoms in 3rd trimester

ruq pain

170

mortality rate of fetus in appendiceal rupture

35% fetal mortality with rupture

171

management of pregnant women with suspected appendicitis

women with suspected appendicitis need beta-HCG drawn and abdominal ultrasound to rule out OB/GYN causes of abdominal pain

172

appendix: can be benign or malignant mucous papillary tumor; needs resection (should open for these so you don't spill tumor contents)

appendix mucocele

173

tx: malignant appendix mucocele

need right hemicolectomy if malignant

174

spread of tumor implants throughout the peritoneum

pseudomyxoma peritonei

175

mcc of death in appendix mucocele

small bowel obstruction from peritoneal tumor srpead

176

can mimic appendicitis; 10% go on to Crohn's disease

regional ileitis

177

nausea, vomiting, diarrhea

gastroenteritis

178

ddx: presumed appendicitis in women

ruptured ovarian cyst, thrombosed ovarian vein, or regional enteritis not involving cecum
- tx: appendectomy (prevents future confounding diagnosis)

179

causes of ileus

surgery (most common), electrolyte abnormalities (decreased K), peritonitis, ischemia, trauma, drugs

180

dilatation is uniform throughout the stomach, small bowel, colon, and rectum without decompression

ileus

181

there is bowel compression distal to the obstruction

obstruction

182

children; get RLQ pain, diarrhea, fever, headaches, maculopapular rash, leukopenia; rare bleeding / perforation
- tx: bactrim

typhoid enteritis (salmonella)