Small Intestines Flashcards by Daniel Coquyt

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

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Conditions clogging biliary ducts

sludging of fluid - biliary sludge
gallstones
pancreatic tumor

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ERCP

Endoscopic retrograde cholangiopancreatogram

Inject contract into ampulla of Vater to visual biliary tree

can cause pancreatitis w/ reversal of flow

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Cholecystokinin (CCK)

I cells of duodenum

“pro duodenal”

decrease gastric emptying
increased pancreatic secretion
Gallbladder contraction

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Secretin

S cells in duodenum

facilitates pancreatic HCO3- secretion neutralizes gastric acid

decreased gastric acid production - inhibit parietal cells

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Gastric Inhibitory Peptide (GIP)

K cells
Decreased gastric acid production
increase insulin release - why PO glucose taken up by cells faster than IV glucose

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Brunner glands

secrete alkaline mucus to neutralize gastric acid

hypertrophy w/ excess acid

only in duodenal submucosa

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Somatostatin

Inhibit secretion of:
gastrin
CCK
secretin
GIP
VIP
insulin
glucagon

D cells in GI and delta cells in pancreas

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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

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Motilin

produces migrating motor complexes

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Ileus

no peristalsis

post op
stroke
septic shock

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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

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Carbohydrate digestion and absorption

salivary amylase

pancreatic amylase –> disaccharides
Intestinal brush border enzymes –> monosaccharies

Glucose and galactose –> sodium dependent transporter

Fructose –> facilitated diffusion

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Protein digestion and absorption

Pancreatic proteases –>

aa –> sodium dependent transport

di-, tri-peptides –> H+ gradient = faster

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Trypsinogen

autoactivation or enterokinase in brushborder –> trypsin

cleaves arginine and lysine

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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) ```