USMLE GI Flashcards
What cells are involved in carcinoid syndrome?
Neuroendocrine cells from carcinoid tumors
Symptoms of carcinoid syndrome?
Recurrent diarrhea, cutaneous flushing, asthmatic wheezing and R sided valvular heart disease
What would you see in the urine of carcinoid syndrome?
Increased 5-hydroxyindoleacetic (5-HIAA) urine
There is increased amount of serotonin being released
Tx of carcinoid syndrome?
Surgical resection, somatostatin analogue (octreotide)
Veins implicated in esophageal varices? Caput medusae? Anorectal varices?
Esophageal - L gastric to azygos
Caput - paraumbilical to small epigastric veins of anterior abd wall
Anorectal - superior rectal to middle and inferior rectal
Honey in those younger than 1 is implicated in which bacteria?
C. botulinum and its spores
Can cause “floppy” head
Symptoms of botulism
Four D’s = diplopia, dysarthria, dysphagia and dyspnea
Tx: human botulinum immunoglobulin
Difference between C botulinum and C tetani?
C botulinum - toxin inhibits Ach release at NMJ
C tetani - produces tetanospasmin, an exotoxin causing tetanus; blocks release of inhibitory release of inhibitor NTs such as GABA and glycine from Renshaw cells in spinal cord
Arteries, veins and lymphatics above and below dentate line?
Artery/vein/lymph above:
superior rectal artery (from IMA), inferior mesenteric vein, internal iliac LN
Artery/vein/lymph below: inferior rectal artery (from internal pudendal a), internal pudendal vein, superficial inguinal LN
ABCDs of C. difficile
Toxin A (enterotoxin) - binds to brush border of gut and alters fluid secretion
Abx use
Toxin B (cytotoxin) - disrupts cytoskeleton via actin depolymerization
Colitis (pseudomembranous)
Difficile/diarrhea
Tx of C diff
Metronidazole or vanco
Fidaxomicin for recurrent cases
Food aversion, wt loss, postprandial epigastric pain
Chronic mesenteric ischemia 2/2 atherosclerosis
Abd pain out of proportion with red “currant jelly” stools
Acute mesenteric ischemia
Crampy abd pain followed by hematochezia
Colonic ischemia
1 gram of protein yields how many calories?
4 calories of energy
Presentation of intestinal atresia
Bilious vomiting, abdominal distention within first 1-2 days of life
Duodenal = failure to recanalize; double bubble sign; associated with Down
Jejunal and ileal = disruption of mesenteric vessels, leading to ischemic necrosis, causing segmental resorption (bowel discontinuity or “apple peel”)
Hyperbilirubinemias (AR)
Gilbert syndrome
Crigler-Najjar, type 1
Dubin-Johnson
Gilbert = mild decreased UDP-glucuronosyltransferase conjugation and impaired bilirubin uptake; asymptomatic or mild jaundice with stress, illness or fasting
Crigler-Najjar = absent UDP-glucuronosyltransferase; pt die within a few years; jaundice, kernicterus (bilirubin deposition in the brain)
Dubin-Johnson = conjugated hyperbilirubinemia due to defective liver excretion of bilirubin glucuronioids; grossly black/dark liver
Thin curvilinear areas of lucency in premature infants
Necrotizing enterocolitis
Where does H pylori preferentially like to colonize?
Gastric antrum
Triple positive of H pylori
Gram negative rod that is catalase +, oxidase + and urease +
Amoxicillin + Clairthromycin + PPI
Gastric ulcers are associated with which part of the stomach? Duodenal ulcers?
Duodenal ulcers = gastric antrum
Gastric ulcers = gastric corpus/body
Lactose intolerance - what enzyme, histology and stool pH
Lactase deficiency
Normal appearing villi
Osmotic diarrhea with decreased stool pH
Tissue type of pancreatic pseudocyst
Fibrous and granulation tissue
Where does lipid absorption take place? Bile absorption?
Lipid - jejenum
Bile acid - terminal ileum
Bile acid resins
Cholestyramine
Colestipol
Colesevelam
Retains bile acids, prevent reabsorption and more is excreted in stool
Three roles of bile
1) digestion and absorption of lipids and fat-soluble vitamins
2) cholesterol excretion
3) antimicrobial activity (via membrane disruption)
Lab findings in cholestasis
Direct/conjugated hyperbilirubinemia
Elevated alk phos
What are markers of biliary disease?
Alk phos, gamma-glutamyl transpeptidase
Name of enzyme involved in conjugation of bilirubin?
UDP-glucuronosyl-transferase
Adding glucuronic acid to make it soluble
Name of molecule that makes your stool dark? Name of molecule that makes your urine yellow?
Stercobilin
Urobilin
Wilson disease characteristics
Movement abnormalities and psych symptoms
Hemachromatosis
Liver disease, skin pigmentation, DM and cardiac enlargement
Four general causes of hyperbilirubinemia
Hemolysis, biliary obstruction, liver disease, special causes
or HOT Liver = hemolysis, obstruction, tumor and liver dz
Lab findings of hemolysis
Increased indirect bilirubin, normal urine bilirubin and increased urobilinogen
Lab findings of obstruction
Increased direct bilirubin, increased urine bilirubin and absent urobilinogen
Two drugs that can cause hyperbilirubinemia
Rifampin (abx for tx of TB)
Probenecid (gout)
Both compete with bilirubin for uptake by liver
Increase in unconjugated bilirubin
Cause of death in Crigler-Najjar syndrome
Kernicterus (bilirubin deposition in brain)
Unconjugated bilirubin is soluble in fats and can easily cross BBB or enter placenta
Drug tx for Crigler-Najjar, type 2
Phenobarbital, clofibrate
Cause of Dubin-Johnson syndrome and characteristic finding
Defective liver excretion
Dark liver
Lab findings of physiologic neonatal jaundice
Increased unconjugated hyperbilirubinemia
2/2 immature UDP-glucuronosyltransferase
Where does bilirubin accumulate in the brain in kernicterus?
Basal ganglia
Tx of neonatal jaundice
Phototherapy which converts bilirubin to lumirubin (more H2O soluble)
Which type of cell in the stomach secretes gastric acid?
Parietal cells found in gastric glands
Three stimuli for acid secretion
Gastrin (direct) binding to CCKb receptor on parietal cells
Gastrin (indirect) activates ECL cells to release histamine, which causes stimulation
Vagus nerve - activates G cells by using gastrin releasing peptide
Role of IF and what releases it?
Necessary for vitamin B12 absorption
Released by parietal cells
Vomiting causes what kind of acid-base physio?
Metabolic alkalosis due to loss of HCl
This causes an increase in HCl production and HCO3 is also generated
Urinary Cl is low
Urinary chloride is useful in?
Determining metabolic alkalosis of unknown cause
Low (<10-20) in vomiting (loss of Cl in gastric secretions)
High (>20) in diuretic use (diuretics block NaCl reabsorption)
Histamine H2 blockers
Cimetidine, ranitidine, famotidine, nizatidine
What activates parietal cell secretion?
What deactivates it?
ACh (Gq), gastrin (Gq) and histamine (Gs/i)
PG (Gs/i) and somatostatin (Gs/i)
Where are G cells found? Parietal cells?
Antrum of stomach
Mucosa of body (parietal cells)
Zollinger-Ellison syndrome
Gastrin secreting tumor
Occurs in duodenum or pancreas (G cells in pancreas)
Excessive acid secretion
AP, chronic diarrhea, ulcers
Tx of gastrinoma
High dose PPI, octeotride (somatostatin)
Pernicious anemia
Autoimmune gastritis, causing loss of parietal cells therefore loss of IF
Cannot absorb vit B12
High gastrin levels
Gastrin stimulates what kind of cells?
Dz associated with this?
Parietal cells
Pernicious anemia (loss of parietal cells, high gastrin levels)
Cholecystokinin
Hormone for gall bladder contraction
Released by I cells (small intestines, D and J)
Secretin
Released by S cells of duodenum
Raises pH in small intestine by pancreatic duct cells!!!
Somatostain
Inhibits most GI hormones
Released by D cells throughout GI tract
Tx of variceal bleeding
Octreotide (used to tx acromegaly, carcinoid syndrome and variceal bleeding)
Glucose-dependent insulinotropic peptide
Released by K cells (duodenum, jejenum)
Oral glucose is metabolized faster than IV glucose
If you administer oral glucose on a pt, GIP will be released
VIPomas
VIP secreting tumor in the pancreas (islet cells)
WDHA (watery diarrhea), hypokalemia, achlorhydria
Tx is octreotide (somatostatin)
How does erythromycin play a role in motility?
Erythromycin binds to motilin receptors. Motilin is released by cells in the stomach, intestines and colon. Used to tx gastroparesis
What enzyme converts trypsinogen to trypsin?
Enterokinase/enteropeptidase
Brush-border enzyme on duodenal and jejunal mucosa
What types of cells can you see in reflux esophagitis?
Eosinophils
This commonly leads to esophageal stricture formation
Consumption of lye (alkali substances), causing liquefactive necrosis that can later cause strictures
Cause of esophagitis
GERD
Candida - white pseudomembrane
HSV-1 - punched out ulcers
CMV - linear ulcers
Pathophys of achalasia (primary and secondary)
Primary: loss of ganglion cells in Auerbach’s plexus (myenteric) in muscularis therefore dysphagia to solids and liquids
Secondary: Chronic Chagas dz
Diagnostic testing of achalasia
Increased LES tone in esophageal manometry
Barium swallow
Which layer of esophagus is involved in Mallory Weiss?
Mucosa at GE junction
Painful hematemesis
Which layer of esophagus is involved in BoerHaave syndrome?
Transmural rupture
Air exits esophagus -> air in mediastinum and under skin in neck
Findings in Plummer-Vinson syndrome
Iron deficiency anemia
Beefy red tongue
Esophageal web
Common in middle-age, white women
Triad of dysphasia, iron deficiency and esophageal webs (DIE)
Which muscle is implicated in Zenker’s diverticulum?
Cricopharyngeal muscle (which allows food to pass)
Classic location: Killian’s triangle between thyropharyngeus muscle and cricopharyngeus muscle
What causes high GGT?
Alcohol use
Which zone is affected first in alcoholic liver dz? (Where does fatty infiltration occur?)
Zone III (near hepatic vein)
Viral hepatitis affects which zone first?
Zone I
When do you see ALT > AST?
Nonalcoholic fatty liver dz
What is associated with non-alcoholic fatty liver dz?
Obesity
Histology of alcoholic hepatitis
Mallory bodies (intracytoplasmic eosinophilic inclusions of damaged keratin/intermediate filaments)
Nutmeg liver
Budd-Chiari syndrome
RHF
Reye syndrome
Children with viral infections who take ASA
Chicken pox and influenza B
These pts have rapid, severe liver failure, as ASA inhibits beta oxidation, damaging mitochondria
Alpha1 anti-trypsin deficiency
Emphysema and cirrhosis are seen
Imbalance b/w elastase and elastase inhibitor AAT (which protects elastin) - emphysema
Abnormal alpha1 builds up in liver, pathologic polymerization of AAT - cirrhosis
Stain purple with PAS
Two bacteria involved in liver abscess
Entamoeba histolytica (protozoa)
Echinococcus (helminth)
Tx of Tylenol (acetaminophen) OD
N-acetylcysteine
Tx of hyperammonemia
Low protein diet
Lactulose (synthetic disaccharide and laxative) - it gets broken down to FAs, which decrease pH, favoring ammonium levels than ammonia
Portal vein thrombosis
Acute onset abd pain
Splenomegaly
Liver biopsy will be normal
Spontaneous bacterial peritonitis
E. coli and Klebsiella
Tx: cefotaxime
Which cells are implicated in cirrhosis?
Stellate cells = perisinusoidal cell. Secretes TGF-beta, proliferates and produce fibrous tissue
Major contributor to cirrhosis
Which bacteria is implicated in HCC?
Aspergillus. It is a fungus that produces aflatoxin
Lab findings for HCC?
Increased alpha-fetal protein
Common site of metastasis of HCC?
Lung
Associated RF for hepatic adenoma
Contraceptive use, anabolic steroids
Vinyl chloride and arsenic can cause what liver pathology?
Hepatic angiosarcoma
ATP7B gene for Wilson’s dz is found on which chr?
Chr 13
If you suspect someone with Wilson’s dz, what do you do?
Order slit lamp exam
Tx of Wilson’s dz?
Pencillamine
HFE gene in hemochromatosis?
Chr 6
Most commonly due to homozygous C282Y mutation
Cause of secondary hemochromatosis
Chronic transfusion therapy for beta-thal major
What should pts with hemochromatosis NOT consume?
Alcohol, vitamin C
Lab tests for hemochromatosis (iron, ferritin, transferrin, % saturation transferrin)
Increased iron
Increased ferritin
Decreased/normal transferrin/TIBC
% saturation transferrin
Tx of hemochromatosis
phlebotomy
Four RFs of gallstones?
4 F’s = female, forty, fat, fertile (multiparity)
If an elderly pt has gallstone symptoms, think CA
Other RFs for gallstones?
Excess estrogen
Altered lipid metabolism
Loss of bile salts
What causes the pain seen in biliary colic?
Pain after eating, esp fatty meals
CCK stimulates gallbladder contraction
Choledocholithiasis
Presence of gallstone common bile duct, often leading to elevated ALP, GGT, direct bilirubin and/or AST/ALT
Porcelain gallbladder
Calcified gallbladder
Increased rate of gallbladder CA
Charcot’s triad
Reynolds pentad
Fever, abd pain, jaundice (part of ascending cholangitis)
Charcot + confusion + hypotension
Bacterial causes of ascending cholangitis
E. coli, Klebsiella, Enterobacter
Rare cause: Clonorchis sinensis (will see peripheral eosinophilia)
Air in the biliary tree
Gallstone ileus, where massive gallstone erodes through gallbladder wall
Creation of a fistula with small intestine
Common bacteria that causes gallbladder carcinoma
Salmonella typhi
Primary biliary cirrhosis
Autoimmune disorder with T cell attacking the small intralobular bile ducts
Granulomatous inflammation
Dx of primary biliary cirrhosis
Anti-mitochondrial antibodies, markedly elevated alk phos
What condition is associated with primary biliary cirrhosis?
Sjogren
What condition is associated with primary sclerosing cholangitis?
Ulcerative colitis
Lab findings (dx) of primary sclerosing cholangitis
Elevated IgM, positive p-ANCA
Pathology of primary sclerosing cholangitis
Periductal fibrosis
Alternating strictures
Beading of intra- and extra-hepatic bile ducts
What can cause cholangiocarcinoma?
Primary sclerosing cholangitis (UC)
Clonorchis sinensis (Chinese liver fluke)
Curling ulcer
Occurs in burn pts
Loss of skin -> loss of fluids -> dehydration -> hypotension to stomach -> mucosal damage
Result: acute gastritis and ulcers
Cushing ulcer
Increased vagal stimulation
Increased ACh
Increased H production
Autoimmune gastritis vs H pylori gastritis
Autoimmune - destruction of gastric parietal cells, therefore body/fundus is affected first
H pylori -
Where does H pylori affect first?
Antrum of stomach
Which CA is associated with H pylori?
MALT lymphoma (B-cell CA)
Which enzyme is more specific for pancreatic damage?
Lipase
If you see ulcers in duodenum or jejenum, what should you suspect?
Zollinger-Ellison syndrome
Brunner’s glands
Found in duodenum in submucosa
Produces alkaline (basic) fluid; thick in peptic ulcer dz
Odd RFs of intestinal gastric CA?
Type A blood
Nitrosamines found in smoked meats
Histology of diffuse gastric CA?
Signet ring cells and linitis plastica (stomach thickened like leather)
Which CA is acanthosis nigricans associated with?
Gastric carcinoma
Menetrier disease
Hyperplasia of gastric mucosa; excessive gastric mucous secretions and loss of acid
Protein loss, hypoalbuminemia
Can lead to gastric adenocarcinoma
Celiac sprue is what type of HS?
Type IV
Associated with HLA-DQ2, HLA-DQ8
Histology of celiac dz
Blunting of villi
Crypt hyperplasia
Lymphocytes in lamina propria
Antibody for celiac dz
IgA anti-tissue transglutaminase
IgA anti-endomysial
Anti-gliadin
Most commonly affected area in celiac dz
Duodenum
What CA is associated with celiac dz?
T-cell lymphoma
Skin condition associated with celiac dz?
Dermatitis herpetiformis
Bacteria that causes Whipple dz
Tropheryma whipplei
Four cardinal features of Whipple dz
Diarrhea
Abd pain
Wt loss
Joint pain
Marker for autoimmune pancreatitis
IgG4 positive plasma cells
One of the main complications of acute pancreatitis
Pseudocyst (lined by granulation tissue, not epithelium)
Fat necrosis can lead to?
Hypocalcemia/hypomg
Two common causes of chronic pancreatitis
Alcohol abuse in adults
CF in kids
Trousseau syndrome
Migratory thrombophlebitis in pancreatic CA
Appendicitis pathogenesis
Fecaliths in adults
Lymphoid hyperplasia in kids
Where does a false diverticulum usually occur?
Where the vasa recta perforate muscularis externa
Where does diverticulosis occur? What typically causes it?
Sigmoid colon
Straining to pass stool (wall stress); low fiber diet
Most common cause of SBO
Adhesions
Currant jelly findings
Intussusception
Medical injury, near the ileocecal junction
Common lead point (intussusception) in kids and adults?
Kids - Meckel diverticulum
Adults - intraluminal mass/tumor
KNOW: adenovirus (STRONG association)
Peyer patch hypertrophy
Which volvulus is more common in elderly? Kids?
Sigmoid in adults
Midgut volvulus in kids
SBO common causes vs LBO
Adhesion
Bulge
CA
LBO; CA, adhesions, volvulus
Pathophys of Hirschsprung’s dz
Absent ganglion cells (derived from neural crest cells)
Nerve cells of Meissner’s plexus and Auerbach’s pleux
Failure to migrate
Ogilvie syndrome
Acute “pseudo-obstruction” of intestines; dilated colon in asbence if a lesion
Usually hospitalized or nursing home pts
Often severe illness or recent surgery
Often associated with narcotics
Major RF for necrotizing enterocolitis
Prematurity
Classic XR finding of necrotizing enterocolitis
Pneumatosis intestinalis
Angiodysplasia is common where?
Cecum and R sided colon
Caused hy high wall stress
Leads to lower GI bleeding
Osler-Weber-Rendu syndrome
aka hereditary hemorrhagic telangiectasia
AD
Telangiectasias throughout GI tract
Rarely leads to AVMs
Common clinical features: nose bleeds, GI bleeding, Fe deficiency
Feared complication of UC
Toxic megacolon
Evidence of nitric oxide that inhibits smooth muscle tone; can cause perforation
Antibody tests for UC and Crohn
UC - p-ANCA
Crohn - anti-saccharomyces cerevisiae antibodies (ASCA)
Common location of Crohn
Terminal ileum
Therefore malabsorption, vit B12 deficiency, malabsorption of bile salts
RLQ
Immunology of Crohn and UC
Th1 for Crohn
Th2 for UC
Tx’s of UC
Sulfasalazine (gets broken down into 5-aminosalicylic acid 5-ASA)
Mesalamine (5-ASA)
Common side effect of sulfasalazine
Oligospermia in men
Benign and most common polyps
Hyperplastic
Peutz-Jeghers syndrome
AD, multiple hamartomas throughout GI tract
Pigmented spots on lips and buccal mucosa
Risk of gastric, small intestinal and colon CA
Three genetics of colon CA
1) two genetic pathways (chromosomal instability, and microsatellite)
2) cyclooxygenase-2 expression increased in colon CA
3) DCC gene mutated in advanced colorectal CA
Chromosomal instability pathway of colorectal CA
Loss of APC gene
KRAS mutation
Loss of tumor suppressor gene (p53)
AK-53
Gardner syndrome
FAP + osseous and soft tissue tumors, congenital hypertrophy of retinal pigment epithelium and impacted/supernumerary teeth
Turcot syndrome
FAP + brain tumor (medulloblastoma)
Microsatellite instability
Mismatch of microsatellites (short repeating segments of DNA)
Lynch syndrome
Hereditary nonpolyposis colorectal CA (HNPCC)
Inherited mutation of DNA mismatch repair enzymes; leads to colon CA via microsatellite instability
Most common non-colon malignancy in Lynch syndrome
Endometrial CA
Gene implicated in colorectal CA
DCC gene
Defect in colorectal gene
S bovis endocarditis is identified. What test is next?
Colonoscopy to screen for colorectal CA
Tumor marker for colorectal CA
Carcinoembryonic antigen
CEA
Vitamin B3 is derived from what aa?
Tryptophan
Can see pellagra in carcinoid syndrome since tryptophan is used to make serotonin
Clinical manifestations of carcinoid syndrome
Recurrent diarrhea, cutaneous flushing, asthmatic wheezing, R sided valvular heart dz
Tx of carcinoid syndrome
Octreotide
Milk alkali syndrome
High intake of calcium carbonate (ulcers)
Triad: hypercalcemia, metabolic alkalosis and renal failure
Side effects of aluminum hydroxide
Constipation, phosphate binder therefore hypophosphatemia
Side effects of Mg hydroxide
Diarrhea, hyporeflexia, hypotension, cardiac arrest
Antacids can affect the drug absorption of which drug?
Tetracycline
Fluorquinolones
Isoniazid
Fe supplements
Common side effect of histamine (H2) blockers
Confusion, esp among elderly
Side effects of cimetidine
1st H2 blocker
Potent P450 inhibitor
Antiandrogen (gynecomastia, impotence, PRL release)
Crosses BBB (dizziness, confusion, HA)
Reduces creatinine excretion
Side effects of PPIs
C diff infection (loss of protection from H)
Pneumonia (more pathogens)
Malabsorption therefore low Mg and Ca therefore hip fractures
Mechanism of ondansetron
What is it good for?
5-HT3 antagonist
For those undergoing CA chemotherapy
Mechanism of metoclopramide
D2 receptor antagonists
Dopamine blocks ACh effects, therefore causing increased esophagus and gastric motility
Used in gastroparesis
AEs of metoclopramide
Drowsiness
Parkinsonian effects
CI of meteoclopramide
Known sz disorders
Parkinson’s dz
BO
Which enzyme is absent in galactosemia?
Galactose-1-phosphate uridyltransferase
Which gene is implicated in familial adenomatous polyposis?
APC gene
Most common benign liver tumor
Cavernous hemangioma
