Chapter 35 - Small Bowel Flashcards
What is absorbed in the small intestine?
nutrients and water
What is absorbed in the large intestine?
Water
In what portion of the duodenum are most ulcers?
bulb- 90%
What is contained in the second/descending portion of the duodenum?
ampulla of vater and duct of santorini
What portions of the duodenum are retroperitoneal?
descending (2nd) and transverse (3rd)
vascular supply of duodenum superiorly? inferiorly?
GDA superiorly, Inferior pancreaticoduodenal
How long is the jejunem?, how large are the vasa recta?
100cm, long vasa recta
The jejunum is the maximum site of absorption for everything except:
B12 - terminal ileum
Bile acids- ileum/terminal ileum
iron- duodenum
Folate- terminal ileum
What percentage of NaCl is absorbed in the jejunem? water?
95%; 90%
What is the vascular supply of jejunum?
SMA
Hos long is the ileum?
150cm, short vasa recta, flat.
Vascular supply from SMA
What is absorbed at the intestinal brush border?
maltase, sucrase, limit dextrinase, lactase
What is the normal diameter of small bowel? transverse colon? cecum?
3 6 9cm.
What is the terminal branch of the SMA?
Ileocolic
What do goblet cells do?
mucin secretion
What do paneth cells do?
secretory granules, enzymes
What do enterochromaffin cells do?
APUD, 5-Hydroxytryptamine release, carcinoid precursor
What do brunner’s glands produce?
alkaline solution
What are peyer’s patches? Where are they increased?
lymphoid tissue; increased in the ileum
What are M-cells?
antigen presenting cells in intestinal wall
What are the phases of gut motility?
I - Rest
II - acceleration and gallbladder contraction
III - peristalsis
IV - deceleration
Motilin is most important hormone in migrating motor complex
What is fat and cholesterol broken down by?
cholesterol esteras, phospholipase A, lipas, colipase in combination with bile salts
- form micelles
- TAG’s are reformed in intestinal cells and released as chylomicrons
What are chylomicrons made up of?
90%TAG’s, 10% phospholipids, cholesterol, protein
What percentage of bile salts are reabsorbed?
95%
- 50% passive- 45% ileum and 5% colon
- 50% active resorption in terminal ileum
- conjugated bile is only absorbed in terminal ileum
What is bile conjugated to?
taurine and glycine
can be deconjugated in the colon by bacteria and absorbed there
What are the primary bile acids?
cholic and chenodeoxycholic
What are the secondary bile acids?
deoxycholic and lithiocholic (from bacterial action on primary bile acids in the gut)
What can happen with the gall bladder after a terminal ileum resection?
develop stones secondary to inability to reabsorb bile salts
How is short gut syndrome diagnosed?
symptoms, not length of bowel
- diarrhea
- steatorrhea
- weight loss
- nutritional deficiency
- Lose fat, B12, electrolytes, water
What is a sudan red test?
checks for fecal fat
What is a schilling test?
checks for B12 absorption
-radiolabeled B12 in urine
how much bowel do you need to survive with TPN?
75cm, 50cm with a competent ileocecal valve
What are the causes of steatorrhea?
gastric hypersecretion of acid- increases motility- interferes with fat absorption
-Interruption of bile salt resorption- interferes with micelle formation
Tx:control diarrhea- lomotil, codeine, decreased oral intake
Causes of Non-healing fistula?
FRIENDS F foreign body R radiation I irritable bowel E epithelialization N neoplasm D distal obstruction S sepsis/infection
High output fistulas normally occur where?
proximal bowel and are less likely to close with conservative management
What are most fistulas caused by?
iatrogenic
- treat conservatively first
- 40% close spontaneously
- can resect bowel secoment and perform primary anastamosis
Obstruction without previous surgery usually caused by what?
small bowel- hernia
large bowel- cancer
Obstruction with previous surgery usually caused by what?
small bowel- adhesions
large bowel- cancer
symptoms of bowel obstruction?
nausea, vomitting, crampy pain, failure to pass gas or stool
-x-ray shows air fluid level, distended loops of small bowel, distal compression
What is the air with bowel obstruction from?
swallowed nitrogen
Conservative treatment for SBO?
NG
IVF
-cures 80% of partial SBO, 20-40% of complete SBO
What are the surgical indications for bowel obstruction?
Progressing pain, peritoneal signs, fever, increasing of WBC’s, signs of strangulation or perforation, failure to resolve
What is gallstone ileus?
- SBO from gallstone in terminal ileum
- Air in biliary tree with SBO
- caused by fistula bw gall bladder and second portion of duodenum
- tx with stone removal
- if sick leave fistula
- if ok remove gall bladder, fix bowel
What is meckel’s diverticulum?
- A true diverticulum
- 2% of population
- 2 feet from ileocecal valve
- fist 2 years of life
What is meckel’s diverticulum caused by?
failure of closure of omphalomesenteric duct
50% of all painless lower GI bleeds in children under 2
What is the most common tissue type found in meckel’s diverticulum? most common to cause bleeds?
Pancreas is most common type.
Gastric mucosa most common to bleed
What is the most common presentation of meckels in adults?
obstruction
How do you localize a meckels?
Meckel’s scan (99Tc)- can do diverticulectomy
What do you do with duodenal diverticula?
observe unless perfrorated?
need to rule out gall bladder disease as a cause
-duodenal>jejunal>ileal
-segmental resection
What are the first signs of Crohn’s disease?
Intermittent abdominal pain, diarrhea, weight loss, low grade fever
- usually 15-35 at first presentation
- increased in ashkenazia J’s
What are the extraintestinal manifestations of crohn’s?
arthritis arthralgias pyoderma gangrenosum erythema nodosum ocular diseases stunted growth (shut your goddamn mouth) B12/Folate deficiency
What is most comon first involved bowel portion?
terminal ileum (40%)
- 10% anal perianal first
- colon only 35%
- small bowel only 20%
What is the pathology of chrons?
transmural involvement segmental- skip lesions cobblestoning narrow deep ulcers creeping fat fistulas
What is medical tx of chrons?
5-ASA sulfasalazine steroids azathioprine methotrexate remicade Loperamide
What are the surgical indications?
90% will need surgery?
- obstruction
- abscess
- megacolon
- hemorrhage
- blind loop obstruction
- fissures
- EC fistula
- Perineal fistula
- anorectovaginal fistulas
What do u do with incidental finding of IBD with normal appendix in presumed appendicitis?
take appendix if cecum not involved
When is stricturoplasty indicated in patients with Chron’s?
multiple strictures to save small bowel length
not good for first operation
10% leakage/abscess/fistula rate with stricturoplasty
What are the complications from removal of terminal ileum?
decreased B12 uptake
decreased bile salt uptake
decreased oxalate binding secondary to increased intraluminal fat that binds calcium–> ca oxalate kidney stones
gallstones
What are kulchitsky cells?
produce serotonin (enterochromoffin cell or argentaffin cells)
what is the breakdown product of serotonin?
5-HIAA can be found in urine
serotonin is part of what GI system?
amine precursor uptake decarboxylase system - APUD
what is the precursor to serotonin?
tryptophan
what can increased levels of tryptophan lead to?
niacin deficiency and pellagra
other than serotonin, what do carcinoid tumors also secrete?
bradykinin
When do you get carcinoid syndrome?
bulky liver mets
flushing and diarrhea
asthma symptoms and right heart valve lesions
how do you treat carcinoid syndrome?
all pts get abdominal exploration unless unresectable
if resecting liver mets, also do cholecystecomy
What are the GI sx in carcinoid caused by?
vasoconstriction and fibrotic desmoplastic rxn
what is a good test for localizing carcinoid when cant find it on CT?
octreotide scan
where is the most common site for carcinoid?
appendix
small bowel carcenoid is at increased risk for what?
multiple primaries and second unrelated malignancies
what do you do with carcinoid in appendix?
2 cm or involving base - right hemi
what do you do with carcinoid anywhere else in GI tract?
treat like ca- segmental resection w lymphadenectomy
What is chemo for carcinoid?
streptozocin and 5FU
what is a palliative tx for carcinoid?
octreotide
what do you do for bronchospasm in carcinoid? flushing? false 5-HIAA is from what? what can exacerbate sx?
Aprotinin
alpha blockers
fruits
pentagastrin
What causes intussusception in adults?
small bowel or cecal tumors
presents with bleeding or obstruction
resection
what is most common small bowel tumor?
leiomyoma- usually extraluminal
where are most adenomas of small bowel found?
ileum
what inheritence is peutz-jehgers? What are sx?
autosomal dominant
- jejunal and ileal hamartomas
- mucocutaneous melanotic skin pigmentation
- extraintestinal malignancies
- slight increase in colon ca
- lipomas, neurogenic tumors
- hemangiomas
what is most common small bowel malignancy?
adenocarcinoma
most in duodenum
may need whipple
what are risks for duodenal ca?
FAP gardners polyps adenomas von recklinghausens
where are leiomyosarcomas of small bowel usually found?
jejunum and ileum
most extraluminal
hard to differenciate from leiomyoma
where are small bowel lymphomas usually found?
ileum
mediterranean variant occurs in young males- they get clubbing
what is obstruction rate with loop ileostomies?
1-2%
what types of ostomies have increased risk of parastomal hernia?
loop colostomies
what is most common stomal infection?
candida
when do you get diversion colitis and from what?
Harmann’s pouch
secondary to decreased short chain fatty acids- give short chain FA enemas
what is most common cause of stenosis of stoma?
ischemia
tx with dilation
what are abscesses under stoma site caused by?
irrigation device
what ostomy pts have increased risk of gallstones and uric acid stones?
ileostomy
sx of appendicitis?
1 anorexia 2 periumbilical pain 3 vomiting 4 migrates to RLQ can have Normal WBC
most common age for appendicitis?
20-35
what does appendicitis look like on CT?
diameter >7mm, wall >2mm, looks like bulls eye, fat stranding, no contrast in lumen
What part of appendix is most likely to perf?
midpoint of antimesenteric border
What is most common cause of appendicitis in children?
hyperplasia- can follow viral illness
most common cause of appendicitis in kids?
fecalith
luminal distention followed by distention of appendix, venous congestion/thrombosis, ischemia, gangrene necrosis, rupture
when is appendicitis non-operative?
walled off perforated appendix
perc drainage and interval appendectomy
f/u barium enema or colonoscopy to ro perf’d colon ca
why are children and elderly more likely to perf?
delayed dx
kids have higher fever, vomitting, diarrhea
elderly may be asymptomatic
Infants rarely get it
what do you do abt appendicitis in pregos?
most common cause of acute abdominal pain in 1st tri
more likely in second tri
more likely to perf in third tri (confused for contractions)
Need to make incision where pain is- displaced superior
what is fetal mortality with perf’d appendix?
35%
what is a mucocele?
can be benign or malignant mucous papillary adenocarcinoma
- right hemi if malignant
- can get pseudomyxoma peritonei w rupture
What percentage of pts with regional ileitis go on to have chron’s?
10%
what do you do if you have presumed appendicitis but find ruptured ovarian cyst or thrombosed ovarian vein?
do appy anyway
most common cause of ileus?
surgery trauma hypokalemia ischemia drugs dilatation is uniform
What do you get with typhoid enteritis?
bleeding/perforation fever headaches maculopapular rash leukopenia tx with bactrim
