chapter 35: small bowel. Flashcards
intestine: nutrient and water absorption
small intestine
intestine: water absorption
large intestine
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)
portions of the duodenum that are retroperitoneal
descending and transverse portions
transition point of the 3rd and 4th portions of the duodenum
acute angle between the aorta (posterior) and SMA (anterior)
vascular supply duodenum
superior (off gastroduodenal artery) and inferior (off SMA) pancreaticoduodenal arteries
- both have anterior and posterior branches
- many communications between these arteries
100 cm long; long vasa recta, circular muscle folds
- absorbs 95% NaCl and 90% water
- vascular supply: SMA
Jejunum
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
150 cm long, short vasa recta, flat
- vascular supply: sma
ileum
what is absorbed at the intestinal brush border?
maltase, sucrase, limit dextrinase, lactase
normal sizes: small bowel / transverse colon / cecum
3 / 6 / 9 cm
SMA eventually branches into the…
ileocolic artery
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
What do goblet cells secrete?
mucin secretion
What do paneth cells secrete?
secretory granules, enzymes
What do enterochromaffin cells secrete?
APUD, 5-hydroxytryptamine release, carcinoid precursor
What do brunner’s cells secrete?
alkaline solution
What do M cells secrete?
antigen-presenting cells in intestinal wall
released into the gut; also in mother’s milk
IgA
small bowel has both heme and Fe transporters
Fe
where is iron absorbed?
duodenum
where is folate absorbed?
terminal ileum
where is b12 absorbed?
terminal ileum
where are bile acids absorbed?
- ileum: non conjugated
- terminal ileum: conjugated
what are the phases of migrating motor complex (gut motility)?
phase 1: rest
2: acceleration and gallbladder contraction
3: peristalsis
4: deceleration
Most important hormone in migrating motor complex (Acts on phase 3)
motilin
percent of bile salts reabsorbed
95%
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
When do gallstones form?
gallstones form after terminal ileum resection from malabsorption of bile salts
how is diagnosis of short-gut syndrome made?
symptoms; not length of bowel
diarrhea, steatorrhea, weight loss, nutritional deficiency
- lose fat, B12, electrolytes, water
short-gut syndrome
stains: checks for fecal fat
sudan red stain
test: checks for b12 absorption (radiolabeled b12 in urine)
schilling test
how much bowel do you need to survive off TPN?
75 cm to survive off TPN; 50 cm with competent ileocecal valve
Tx: short gut syndrome
restrict fat, ppi to reduce acid, lomotil (diphenoxylate and atropine)
causes of steatorrhea
- gastric hyper secretion of acid
- interruption of bile salt resorption
how does gastric hyper secretion of acid cause steatorrhea?
decreased pH-> increased intestinal motility; interferes with fat absorption
how does interruption of bile salt resorption cause steatorrhea?
(eg terminal ileum resection) interferes with micelle formation and fat absorption
Tx: steatorrhea
control diarrhea (lomotil); decrease oral intake, especially fats, pancreas, ppi
causes of non healing fistulas
FRIENDS: fistulas, radiation, inflammatory bowel disease, epithelialization, neoplasm, distal obstruction, sepsis/infection
characteristics of high-output fistulas
- more likely with proximal bowel (duodenum or proximal jejunum)
- less likely to close with conservative management
colonic fistulas vs small bowel
- which are more likely to close?
colonic fistulas are more likely to close than those in small bowel
nonhealing fistula: patients with persistent fever
need to check for abscess (fistulogram, abdominal CT, upper GI with small bowel follow through)
treatment: fistulas
most fistulas are iatrogenic and treated conservatively first: NPO, TPN, skin protection (stoma appliance), octreotide
how do most non healing fistulas close?
majority close spontaneously without surgery
surgical options of non healing fistulas
resect bowel segment containing fistula and perform primary anastomosis
MCC obstruction without previous surgery
Small bowel: hernia
Large bowel: cancer
MCC obstruction with previous surgery
Small bowel: adhesions
Large bowel: cancer
- 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)
- 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)
- 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)
- pain: continuous
- vomiting: intermittent, not prominent; feculent when present
- tenderness: diffuse
- distention: marked
- obstipation: present
colon and rectum obstruction
type of bowel obstruction with no distention
proximal small bowel (open loop)
AXR: obstruction
air-fluid level, distended loops of small bowel, distal decompression
tx: 3rd spacing of fluid into bowel lumen with obstruction
need aggressive fluid resuscitaiton
why is there air with bowel obstruction?
from swallowed nitrogen
tx: bowel obstruction
bowel rest, NGT, IVF, -> cures 80% of partial SBO, 40% of complete SBO
obstruction: surgical indications
progressing pain, peritoneal signs, fever, increasing WBCs (all signs of strangulation or perforation), or failure to resolve
small bowel obstruction from gallstone usually in the terminal ileum
gallstone ileus
imaging: what do you see in gallstone ileus?
classically see air in the biliary tree in a patient with small bowel obstruction
what causes gallstone ileus?
caused by a fistula between the gallbladder and second portion of duodenum
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
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
what causes meckel’s diverticulum?
caused by failure of closure of the omphalomesenteric duct
most common tissue found in meckel’s (can cause diverticulitis)
pancreas tissue
most likely to be symptomatic (bleeding most common) - tissue in meckel’s diverticulum
gastric mucosa
two types of tissue in meckel’s diverticulum
pancreatic and gastric tissue
adults: MC presentation of meckel’s diverticulum
obstruction
when do you remove meckel’s diverticulum?
incidental -> usually not removed unless gastric mucosa suspected (diverticulum feels thick) or has a very narrow neck
dx: meckel’s diverticulum
can get a meckel’s scan (99Tc) if having trouble localizing (mucosa lights up)
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
what do you need to rule out in duodenal diverticula?
gallbladder-duodenal fistula
primary management: duodenal diverticula
observation unless perforated, bleeding, causing obstruction, or highly symptomatic
Frequency of duodenal diverticula
Duodenal > jejunal > ileal
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)
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
portion of alimentary where crohn’s occurs
can occur anywhere from mouth to anus; usually spares rectum
extraintestinal manifestations of crohn’s
arthritis, arthralgias, pyoderma gangrenosum, erythema nodosum, ocular diseases, growth failure, megaloblastic anemia from folate and vitamin b12 malabsorption.
crohn’s: most commonly involved bowel segment
terminal ileum
crohn’s: 1st presentation in 5%
anal / perianal disease
- Tx: flagyl
- anal disease most common symptom: large skin tags
crohn’s disease: most common sites for initial presentation
- terminal ileum and cecum: 40%
- colon only: 35%
- small bowel only: 20%
- perianal: 5%
Dx: crohn’s disease
colonoscopy with biopsies and enteroclysis can help make the diagnosis
pathology: crohn’s disease
transmural involvement, segmental disease (skip lesions), cobblestoning, narrow deep ulcers, creeping fat, fistulas
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
crohn’s: agents affecting natural course of disease
no agents affect natural course of disease
may induce remission and fistula closure with small bowel crohn’s disease
TPN
percent of patient needing operation in crohn’s
90%
surgical indications: crohn’s disease
obstruction abscess megacolon hemorrhage blind loop obstruction fissures fistulas: enterocutnaeous, perineal, anarectovaginal
margins in crohn’s surgery
do not need clear margins; just get 2cm away from gross disease with surgery
obstruction: crohn’s
often partial and can be initially treated conservatively
abscess: crohn’s
usually treated with percutaneous drainage
megacolon: crohn’s
perforations occurs in 15%; usually contained
hemorrhage: crohn’s
unusual in crohn’s but can occur
blind loop obstruction: crohn’s
need resection
fissures: crohn’s
no lateral internal sphincteroplasty in patients with crohn’s disease
enterocutaneous fistula: crohn’s
can usually be treated conservatively
perineal fistula: crohn’s
unroof and rule out abscess; let heal on its own
anorectovaginal fistula: crohn’s
may need rectal advancement flap; possible colostomy
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)
tx: incidental finding of IBD in patient with presumed appendicitis who has normal appendix
remove appendix is cecum not involved (avoids future confounding diagnosis)
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)
complications of stricturoplasty
10% leakage/abscess/fistula rate with stricturoplasty (all of which can usually be treated conservatively)
recurrence rate requiring surgery for Crohn’s disease after resection
50% recurrence rate
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
chron’s: mechanisms of megaloblastic anemia
decreased b12 uptake
crohn’s: mechanism of osmotic diarrhea and steatorrhea
decreased bile salt uptake
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
crohns: mechanism of gallstones
can form after terminal ileum resection from malabsorption of bile salts
what produces serotonin in carcinoid?
kulchitsky cells (enterochromaffin cell or argentaffin cell)
what is serotonin (carcinoid) a part of?
part of amine precursor uptake decarboxylase system (APUD)
breakdown product of serotonin - can measure this in urine
5-hiaa
what does carcinoid tumor release?
serotonin
bradykinin
carcinoid: caused by bulky liver metastases
carcinoid syndrome (intermittent flushing - kallikrein ; diarrhea - serotonin)
hallmark symptoms of carcinoid syndrome
intermittent flushing (kallikrein) diarrhea (Serotonin)
- can also get asthma-type symptoms (bradykinin) and right heart valve lesions
what do you think about: if patient has carcinoid syndrome with small bowel carcinoid primary
it indicates metastasis to liver (liver usually clears serotonin)
carcinoid syndrome: what do you do if you perform resection of liver metastases
perform cholecystectomy in case of future embolization
carcinoid: best for localizing tumor not seen on ct scan
octreotide
highest sensitivity for detecting a carcinoid tumor
chromogranin a level
most common site for carcinoid tumor (50% of carcinoids arise here)
appendix carcinoid (ileum and rectum next most common)
carcinoid: site where patients are at increased risk for multiple primaries and second unrelated malignancies
small bowel carcinoid
tx: carcinoid in appendix
- 2cm or involving base
- 2 cm or involving base: right hemicolectomy
tx: carcinoid anywhere else in GI tract aside from appendix
treat like cancer (segmental resection with lymphadenectomy)
chemotherapy for carcinoid
streptozocin and 5FU; usually just for unresectable disease
useful for carcinoid syndrome palliation
octreotide
carcinoid: tx for bronchospasm
aprotinin
carcinoid: tx for flushing
alpha blockers (phenothiazine)
what can cause false elevations in 5-hiaa?
fruits
same colon CA risk as ulcerative colitis
crohn’s pancolitis
- 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
- most found in duodenum; present with bleeding, obstruction
- need resection when identified (often done with endoscope)
Adenomas - benign small bowel tumors
- 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
mc extraintestinal malignancy in peutz-jeghers syndrome
breast cancer
most common malignant small bowel tumor
adenocarcinoma (rare)
where are most small bowel adenocarcinomas found?
high proportion are in the duodenum
Symptoms of adenocarcinoma small bowel
obstruction, jaundice
tx: small bowel adenocarcinoma
resection and adenectomy; Whipple if in 2nd portion of duodenum
duodenal CA risk factors
FAP, Gardner’s, poylps, adenomas, von Recklinghausen’s
- usually in jejunum and ileum; most extraluminal
- hard to differentiate compared with leiomyoma (>5 mitoses/HPF, atypia, necrosis)
leiomyosarcoma
what do you need to rule out in leiomyosarcoma?
make sure it is not a GIST (check for c-kit)
tx: leiomyosarcoma in small bowel
resection; no adenectomy required
- 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
dx: lymphoma - malignant small bowel
abdominal ct, node sampling
tx: lymphoma - small bowel
malignancy: wide en block resection (include nodes) unless 1st or 2nd portion of the duodenum (chemo-XRT, no Whipple)
survival rate small bowel lymphoma
40% 5 year survival rate
highest incidence with colostomies; generally well tolerated and do not need repair unless symptomatic
parastomal hernias
most common stomal infection
candida
(hartmann’s pouch) - secondary to lack of short-chain fatty acids
- tx: short-chain fatty acids enemas
diversion colitis
most common cause of stenosis of stoma
- tx: dilation if mild
ischemia
most common cause of fistula near stoma site
crohn’s disease
underneath stoma stie, often caused by irrigation device
abscesses
increased in patients with ileostomy
gallstones and uric acid kidney stones
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
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
where is the appendix most likely to perforate?
midpoint of anti-mesenteric border
mcc appendicitis in children; can follow a viral illness
hyperplasia
mcc appendicitis in adults
fecalith
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
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.
follow up: nonoperative appendicitis (walled-off perforated appendix)
consider follow-up barium enema or colonoscopy to rule out perforated cecal colon CA
why do children and elderly have higher propensity for appendices rupture?
secondary to delayed diagnosis
children often have higher fever and more vomiting and diarrhea
appendicitis
elderly: signs and symptoms can be minimal; may need right hemicolectomy if cancer suspected
appendicitis
frequency of appendicitis in infants
appendicitis is infrequent in infants
appendicitis: patient generally more ill; can have evidence of sepsis
peforaiton
mcc of acute abdominal pain in the first trimester
appendicitis
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
when in appendicitis more likely to perforate in pregnancy?
more likely to perforate in the third trimester - confused with contractions
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)
appendicitis: possible symptoms in 3rd trimester
ruq pain
mortality rate of fetus in appendiceal rupture
35% fetal mortality with rupture
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
appendix: can be benign or malignant mucous papillary tumor; needs resection (should open for these so you don’t spill tumor contents)
appendix mucocele
tx: malignant appendix mucocele
need right hemicolectomy if malignant
spread of tumor implants throughout the peritoneum
pseudomyxoma peritonei
mcc of death in appendix mucocele
small bowel obstruction from peritoneal tumor srpead
can mimic appendicitis; 10% go on to Crohn’s disease
regional ileitis
nausea, vomiting, diarrhea
gastroenteritis
ddx: presumed appendicitis in women
ruptured ovarian cyst, thrombosed ovarian vein, or regional enteritis not involving cecum
- tx: appendectomy (prevents future confounding diagnosis)
causes of ileus
surgery (most common), electrolyte abnormalities (decreased K), peritonitis, ischemia, trauma, drugs
dilatation is uniform throughout the stomach, small bowel, colon, and rectum without decompression
ileus
there is bowel compression distal to the obstruction
obstruction
children; get RLQ pain, diarrhea, fever, headaches, maculopapular rash, leukopenia; rare bleeding / perforation
- tx: bactrim
typhoid enteritis (salmonella)
