Small Intestines Flashcards
Duodenal atresia
failed to canalize
bilious vomiting, stomach distended
XR: double bubble - stomach w/ gass proximal to pyloris
-distention in blind duodenal pouch
Assoc w/ down syndrome
Conditions clogging biliary ducts
sludging of fluid - biliary sludge
gallstones
pancreatic tumor
ERCP
Endoscopic retrograde cholangiopancreatogram
Inject contract into ampulla of Vater to visual biliary tree
can cause pancreatitis w/ reversal of flow
Cholecystokinin (CCK)
I cells of duodenum
“pro duodenal”
- decrease gastric emptying
- increased pancreatic secretion
- Gallbladder contraction
Secretin
S cells in duodenum
facilitates pancreatic HCO3- secretion neutralizes gastric acid
decreased gastric acid production - inhibit parietal cells
Gastric Inhibitory Peptide (GIP)
K cells
Decreased gastric acid production
increase insulin release - why PO glucose taken up by cells faster than IV glucose
Brunner glands
secrete alkaline mucus to neutralize gastric acid
hypertrophy w/ excess acid
only in duodenal submucosa
Somatostatin
Inhibit secretion of: gastrin CCK secretin GIP VIP insulin glucagon
D cells in GI and delta cells in pancreas
Vasoactive intestinal peptide (VIP)
Produced by sm.m. of GI and parasympathetic ganglia and enteric nervous system
relaxes sm.m. and sphincters throughout GI tract
increased secretion of electrolytes and water –> watery diarrhea
VIPoma of pancreas –> high volume rice water diarrhea like cholera
Motilin
produces migrating motor complexes
Ileus
no peristalsis
post op
stroke
septic shock
Prokinetic agents for ileus
Goal: increase ACh, Increase 5-HT (carcinoid syndrome), decrease D2
Cholinergic agonists - Bethanechol
Aceytlcholinesterase inhibitors - neostigmine
Metoclopramide (Reglan) - stimulates 5HT4, inhibits D2
- used in gastroparesis of DM pts
- SE: seizures, drug induced parkinsonism
Macrolides - stimulate sm.m. motilin receptors
Carbohydrate digestion and absorption
salivary amylase
pancreatic amylase –> disaccharides
Intestinal brush border enzymes –> monosaccharies
Glucose and galactose –> sodium dependent transporter
Fructose –> facilitated diffusion
Protein digestion and absorption
Pancreatic proteases –>
aa –> sodium dependent transport
di-, tri-peptides –> H+ gradient = faster
Trypsinogen
autoactivation or enterokinase in brushborder –> trypsin
cleaves arginine and lysine
Lipid digestion and absorption
salivary lipase and stomach –> triacylglycerol
pancreatic lipase –> FA, 2-monoacylglycerol
Bile salts emulsify hydrolized products –> micelles –> triglycerides, cholesterol –> chylomicrons –> liver
pancreatic lipase deficiency
chronic pancreatic inflammation –> decreased lipase = decreased lipid digestion
Iron absorption and deficiency
duodenum
cause: antacids and certain abx; gastric bypass sx
Folate absorption and deficiency
duodenum
jejunum
Def: poor nutrition (e.g. alcoholism)
Infants exclusively fed goats milk
B12 absorption and deficiency
terminal ileum - requires intrinsic factor
Def: malnutrition, pernicious anemia
Abetalipoproteinemia
AR
Lack apoB –> defective chylomicron assembly
apoB48 tells chylomicron to leave enterocytes - without it it accumulates
Acanthocytes - star shaped RBCs
Presents early childhood: steatorrhea malabsorption - ADEK deficient failure to thrive ataxia
Lactase deficiency
lactase in tips of microvilli
-gastroenteritis can blunt microvilli –> temporary lactose intolerance
sx: bloating, cramping, diarrhea
supplement enzyme or avoid lactose
Tropical sprue
likely infectious cause
can affect entire small bowel
vitamin deficiency
Megaloblastic anemia
not better w/ removal of gluten
better with abx
Whipple disease
Tropheryma whipplei
wt loss LAD hyperpigmentation cardiac sx arthralgias neurological sx
PAS+ foamy macrophages laden w/ t. whipplei in intestinal lamina propria
Older white males
Tx: PCN, ampicillin, tetracycline x 1-2 YEARS!
less than 1 yr tx has 40% relapse rate
Bacteria overgrowth of small intestine
N/V/D
bloating
malabsorption
signs of inflammation on histo
dx: aspirate from jejunum - grow out –> excess growth
risk: dysmotility fistulas diverticula ileocecal valve resection gastroenteritis Meds: PPIs
Tx:
Abx/probiotics - contraversial
Intermittent as relapse common
Pancreatic insufficiency
d/t chronic pancreatitis, CF, obstruction of duct (gallstones, cancer)
fat malabsorption - ADEK def
steatorrhea
Meckel’s diverticulum
MC congenital anomaly in GI
Incomplete obliteration of omphalomesenteric duct (vitilline duct)
five 2's -2 inches long 2 feet from ileocecal valve 2% of population first 2 years of life 2 types of tissue- pancreatic and gastric
It causes: Melena RLQ pain intussusception volvulus obstruction
Intussusception
telescoping of sm. bowel into itself
MC abdominal emergency under 2 yo
Near ileocecal junction
unusual for adults
75% idiopathic
Viruses - esp adenovirus
Currant jelly stools
sudden severe abdominal pain, V
US: “bull’s eye” or “coiled spring”
Intestinal ileus
Lack peristalsis in GI tract
post op or severe illness
d/t decreased blood flow to gut - diverted to areas of healing
Meconium ileus
meconium not passed in first days after birth
causes: CF, hirschsprung dz
Necrotizing enterocolitis
Premature - bowel necrosis, orally fed
sx: feeding intolerance, increaed gastric residuals, abdominal distention, bloody stools
- -> perforation
XR: dilated loops of bowel
paucity of gas
pneumatosis intestinalis - gas in wall of small or large intestine
Tx: bowel rest, parenteral nutrition
Intestinal ischemia
Mesenteric ischemia - small intestine
-has chronic form d/t atherosclerosis; typically pain after eating in older male
Ischemic colitis - large intestine
Causes:
Inadequate blood supply
-watershed of splenic flexure at risk
Splanchnic vasoconstriction
Acute arterial occlusion
Venous thrombosis
hypoperfusion of mesenteric vasculature
Typically elderly patient w/ abdominal pain out of proportion to exam findings
Labs: nonspecific
Plain XR: dilated loops of bowel and bowel wall thickening
CT angio diagnostic
Tx underlying cause:
Venous thrombosis - anticoagulation
Arterial embolism - early surgical laparotomy w/ embolectomy
nonocclusive d/t vasoconstriction - remove vasoconstrictive drugs
bowel necrosis - resect
Angiodysplasia
small vascular malformation in GI
Tend to bleed - unxplained GI bleeding and anemia
Cecum or ascending colon
Dx: colonscopy, angiography
older patients
Irritable bowel syndrome (IBS)
chronic abdominal pain and altered bowel habits
abd pain: crampy w/ variable intensity - improves with defecation
Diarrhea, constipation or alternating
Other sx: GERD, dysphagia, early satiety, nausea, and chest pain
Non GI: urinary frequency and urgency, dysmenorrhea, dyspareunia, fibromyalgia
tx: diet modificaiton (lactose or gluten), fiber supplement, antispasmodics (dicyclomine and hyoscyamine) antidepressants (TCA, SSRI), guanylate cyclase agonists (IBS w/ constipation)
NOT associated: rectal bleeding nocturnal abdominal pain, wt loss, anemia, elevated inflammatory markers, electrolyte abnormalities
Common causes of SBO?
XR: dilated loops of bowel
ABCs
Adhesions - surgical 75%
Bulge - hernia
Cancer - tumors - mets colorectal cancer
Other less common:
volvulus, intussusceptions, Crohn’s dz, gallstone ileus, bezoar, bowel wall hematoma from trauma, inflammatory stricture, congenital malformation, radiaiton enteritis
Carcinoid tumor
neuroendocrine –> hormone secretion
-Histamine, prostaglandin
Most importantly serotonin
50% of small intestinal tumors
Appendix, ileum, rectum, lung
sx d/t excess serotonin –> carcinoid syndrome
If in intestine only liver metabolizes serotonin via first pass, no sx.
Mets outside of GI or primary lung cause sx
Carcinoid syndrome
BFDR Bronchospasm Flushing Diarrhea Right sided valvular heart disease (edema, ascities)
