GI

Question 1

Where are lipids absorbed?

Answer 1

in the jejunum

Question 2

What is a common cause of Zenker diverticulum?

Answer 2

Cricopharyngeal dysfunction: diminished relaxation of pharyngeal mm. during swallowing → ↑P → protrusion of mucosa through muscular layer → false diverticulum

Question 3

What are the symptoms of cricopharyngeal dysfunction?

Answer 3

High dysphagia: difficulty swallowing felt at throat, coughing, choking, occassionally nasal regurgitation

Question 4

What causes achalasia?

Answer 4

degenerative changes of the myenteric plexus

Question 5

How do you test for malabsorption

Answer 5

1. Sudan III stool stain checks for fat in stool
2. Quantitative analysis confirms diagnosis (>7 g/day of excreted fat = malabsorption)
3. Investigate cause using endoscopy, barium studies, etc..

Question 6

Name the part of the duodenum where most duodenal ulcers occur. What are the risks involved with an anterior and a posterior ulcer in this location?

Answer 6

most ulcers occur in the duodenal bulb, right after the stomach; most are anterior → risk of perforation; poster → risk of hemorrhage of gastroduodenal artery

Question 7

What causes the ↓ stool pH in lactose intolerance?

Answer 7

bacterial fermentation of lactose → short-chain FAs and excess H+

Question 8

What happens to the stool osmolar gap in lactose deficient patients?

Answer 8

↑ due to poorly absorbable substances (including fermentation products)

Question 9

Explain the pathogenesis of hepatic encephalopathy

Answer 9

Often triggered by GI bleeding in cirrhotic pt→ ↑ absorption of ammonia (NH4) → NH4 affects brain in two ways:

1. ↑ action of glutamine synthase (glutamate → glutamine) →
   (a) ↑ glutamine → astrocyte hyperosmolar swelling and mitochondrial dysfunction, and
   (b) ↓ glutamate → ↓ ability to excite neurons
2. ↑ action of glutamate dehydrogenase (NH4 + α-ketoglutarate → glutamate) → ↓ α-ketoglutarate (a Kreb’s cycle intermediate) → impaired energy metabolism

Question 10

What is the chemical name for lactose?

Hint: think about what two sugars make the molecule and what links them

Answer 10

Galactosyl β-1, 4-glucose

1, 4-glycosidic linkage b/w glucose and galactose

Question 11

What are the two important histological morphologies of polyps? Which indicates malignancy?

Answer 11

tuberous vs. villous (=villainous = malignant)

Question 12

Failure of what structure to obliterate → Meckel’s diverticulum? Is it a true or false diverticulum?

Answer 12

Omphalomesenteric (vitalline duct); true, meaning it has all wall layers

Question 13

What are the 3 unique characteristics of ulcerative colitis (to differentiate from Chron’s)?

Answer 13

1. the rectum is always involved
2. inflamm. is limited to mucosa and submucosa only
3. mucosal damage is continuous (no areas of normal mucosa b/w affected segments)

Question 14

What are the 3 unique characteristics of Chron’s?

Answer 14

1. transmural inflammation
2. non-caseating granulomas
3. perianal fistulae

Question 15

What are conditions that occur in association with an imperforate anus?

Answer 15

1. Most commonly, fistulas: urorectal, urovesical, or urovaginal → meconium may discharge from the urethra or vagina
2. In up to 50% of pts: Renal agenesis, hypospadias, epispadias, bladder extrophy
3. Less common: VACTERL syndrome (vertebral defects, anal atresia, cardiac abnormalities, tracheoesophageal fistula, esophageal atresia, renal abnormalities, limb abnormalities

Question 16

Contrast the mechanism of gastric vs. duodenal ulceration caused by H. pylori

Answer 16

H. pylori lives in the antrum mucus layer, causing inflammation →

1. Destruction of somatostatin-producing antral cells (mech. unclear) → ↑ acidity → duodenal ulcer
2. Destruction of gastric mucosa → ↓ defense against acid → gastric ulcer (does not require ↑ acidity, just ↓ defense)

Question 17

What finding on liver function is diagnostic for alcoholic hepatitis? What are 2 other findings which can be indicative of chronic alcohol use

Answer 17

AST:ALT ratio > 2; ↑ gamma-glutamyltransferase (GGT) and macrocytosis (due to folate or B12 deficiency or direct EtOH induced BM toxicity)

Question 18

What causes WDHA and how can this condition be treated?

Answer 18

VIPoma - (WDHA = watery diarrhea, hypokalemia, achlorhydria)
VIP causes:
1. ↑ chloride (and bicarb) release from pancreas → loss of H2O, Na+, K+ → diarrhea and hypokalemia
2. ↓ gastric acid secretion → achlorhydria
Somatostatin inhibits release of VIP

Question 19

What are organisms commonly isolated from intraabdominal infections?

Answer 19

E. coli and B. fragilis (most common)
Enterococci
Streptococci

Question 20

Which is deeper in the glands of the stomach: parietal cells or chief cells?

Answer 20

chief cells (secrete pepsinogen)

Question 21

What esophageal condition can mimic unstable angina?

Answer 21

DES - diffuse esophageal spasm; (DES patients have to have a cardiac workup to r/o cardiac cause of pain)

Question 22

What are the steps in the colorectal cancer sequence?

Answer 22

1. APC inactivation → hyperproliferative state → polyp
2. Methylation abnormalities and COX-2 over-expression
3. K-RAS activation → size ↑ in polyp
4. DCC and p53 inactivation → large adenomatous polyp to adenocarcinoma transformation

Question 23

What disease is characterized by PAS-positive granules in macrophages at the lamina propria and steatorrhea?

Answer 23

Whipple’s disease; note that the granules will be resistant to diastase and the macrophages will also have rod-shaped bacilli

Question 24

How are gallstones and osteomalacia related?

Answer 24

gallstones can lead to malabsorption of fat soluble vitamins, including vit D. → impaired Ca2+, PO4 uptake & mineralization of bone

Question 25

What is biliary sludge and what causes its formation?

Answer 25

gallbladder hypomotility → bile ppt → biliary sludge, which contains cholesterol monohydrate crystals, calcium bilirubinate, and mucus; this is a precursor to stone formation

Question 26

What do brown and black gallstones indicate?

Answer 26

brown = biliary tract infection
black = intravascular hemolysis

Question 27

What disease is characterized by antimitochondrial antibodies, lymphocytic infiltrate and granulomas around bile ducts?

Answer 27

primary biliary cirrhosis

Question 28

What does ↑ HBeAg signify?

Answer 28

active viral replication and thus high transmissibility (it is a core protein like HBcAg), especially when there is no Anti-HBeAg

Question 29

What can cause HCC without causing cirrhosis first? Why?

Answer 29

HBV – it is not vert cytotoxic, but integrates into host genome and acts as an oncogene; most people who get it have no symptoms and become immune after fighting it off

Question 30

What causes the spider angiomata in alcoholic cirrhosis?

Answer 30

hyperestrinism

Question 31

What is the triad of late-stage hemochromatosis? What is the worst complication?

Answer 31

aka “bronze diabetes”
1. hyperpigmentation (esp. in sun-exposed areas)
2. diabetes mellitus
3. pigment cirrhosis with hepatomegaly
Could progress to hepatocellular carcinoma

Question 32

What lab test should follow a moderately elevated alkaline phosphatase of unclear etiology? Why?

Answer 32

gamma-glutamyl transpeptidase (GGTP) because it is not present in bone, so can help distinguish if ↑ ALP is hepatic or bony in origin

Question 33

What is Gilbert syndrome?

Answer 33

reduced UDP-glucuronyl transfereases → ↑ unconjugated billirubin → jaundice after trigger s.a. hemolysis, fasting, physical exertion, febrile illness, stress, or fatigue