GI

Question 1

Linkage disequilibrium

Answer 1

When a pair of alleles are inherited together in the same gamete (haplotype) more or less often than would be expected given random chance

Question 2

Gallstone ileus

1. What is it?
2. Presentation
3. Dx

Answer 2

1. Obstruction in the ileum due to passage of a large gallstone through a cholecystenteric fistula in the small bowel
2. SBO
3. Dx: Ab XR may reveal gas within the gallbladder and biliary tree

Question 3

Positive Predictive Value

Answer 3

The proportion of indivudals with positive test results who actually have the dz

PPV = TP/ (TP + FP)

Question 4

Between positive/ negative predicative values, and sensitivity/ specificty, which are dependent on disease prevalence in the tested population?

Answer 4

Positive/ negative predictive values

Question 5

Enteropeptidase

1. What secretes it?
2. What does it do?
3. What does its deficiency lead to?

Answer 5

1. Comes from the jejunal brush border
2. Activates trypsin from trypsinogen (needed for peptide breakdown and activation of other pancreatic enzymes)
3. Deficiency impairs protein and fat absorption

Question 6

Where are dietary lipids digested? Where are they absorbed?

Answer 6

1. Digestion: in the duodenum via pancreatic enzymes
2. Absorbed: in the jejunum in the form of water-soluble micelles

Question 7

What type of MHC do APCs express?

Answer 7

MHC Class II so that they can present antigen to CD4 cells

Question 8

Inherited defects involving what signaling pathway, result in disseminated mycobacterial dz in infancy/ early childhood?

Answer 8

Interferon-gamma

(needed to activate macrophages)

Question 9

Where does the gastroduodenal artery sit? How can it be affected by ulceration?

Answer 9

It lies along the posterior wall of the duodenal bulb. It is likely to be eroded by posterior duodenal ulcers, leading to potential life-threatening hemorrhage.

Question 10

Meckel diverticulum

1. What is it/ How common is it?
2. What causes it?

Answer 10

1. The most common congenital anomaly of the small intestine
2. It forms due to incomplete obliteration of the omphalomesenteric duct that connects the midgut lumen and yolk sac cavity

Question 11

What types of tissues are comonly found in a Meckel diverticulum? Which is most common?

The presence of these tissues is an example of what?

Answer 11

Gastric (most common), pancreatic, colonic, endometrial, small bowell, etc.

This is an example of ectopy

Question 12

Presentation of Meckel diverticulum

Answer 12

Most often presents with painless melena (gastric tissue can cause ulceration leading to lower GI bleed). The diverticulum may also become inflamed and simulate presentation of acute appendicitis.

Question 13

1. What is the cause of umbilical hernias?
2. What conditions are they associated with?

Answer 13

1. Incomplete closure of the umbilical ring
2. Dat Big Hernia –> assc. w/ Down Syndrome, Beckwith-Wiedmann syndrome, Hypothyroidism

Question 14

What type of polyps are most likely to undergo malignant transformation?

Answer 14

Villous adenomas

Question 15

Vitamin E deficiency

1. Who does it occur in?
2. What is defiency in this vitamin associated with?
3. Clinical manifestations

Answer 15

1. Can occur in individuals with fat malabsorption
2. Assc. w/ inc. susceptibility of the neuronal and erythrocyte membranes to oxidative stress
3. Clinical manifestations: ataxia, impaired proprioception and vibratory sensation, and hemolytic anemia

Question 16

Normal Vitamin E function

Answer 16

Protection of fatty acids against oxidation

Question 17

What type of drug is useful for nausea assc. with GI insults?

For nausea assc. with migraine?

Answer 17

GI: 5-HT3 receptor antagonists

Migraine: Dopamine antagonists

Question 18

What is the best non-surgical tx for cholesterol gallstones?

Answer 18

Hydrophilic bile acids (eg ursodeoxycholic acid). These decrease biliary cholesterol secretion and increase biliary bile acid concentration, improving cholesterol solubulity.

Question 19

How is Campylobacter infection spread?

Answer 19

Via domestic animals or from contaminated food

Question 20

Inapparopriate activation of what enzyme, leads to pancreatitis?

Answer 20

Trypsinogen (to trypsin)

Question 21

1. Pernicious anemia (Vit B12 def.) is caused by autoimmune destruction of what cells?
2. What do these cells secrete and where are they located?

Answer 21

1. Destruction of parietal cells (chronic atrophic gastritis).
2. They secrete HCL and IF, and are found primarily in the superficial region of the gastric glands

Question 22

What are the (3) tx for C.diff and in what situation would you use each?

Answer 22

1. Metronidazole (Initial mild/moderate C. Diff tx)
2. Vancomycin (Severe or recurrent C. Diff)
3. Fidaxomicin (recurrent C. Diff and inc. risk of recurrence)

Question 23

The venous component of internal hemorrhoids drain where?

External hemorrhoids?

Answer 23

Internal: drain into the middle and superior rectal veins, which communicate with the internal iliac and inferior mesenteric veins

External: drain via the inferior rectal vein into the internal pudendal vein, which communicates with the internal iliac veins

Question 24

Primary Biliary Cirrhosis/ Cholangitis

1. What characterizes this dz?
2. Who is it common in ?
3. Presentation?

Answer 24

1. Chronic liver dz characterized by autoimmune destruction of the intrahepatic bile ducts and cholestasis (elevated alk phos)
2. Most common in middle aged women
3. Sx: Severe pruritis (especially at night)

Question 25

What is the main dz Primary Biliary Cirrhosis (PBC) is associated with?

Answer 25

Sjrogren's syndrome (and other autoimmune disorders)

Question 26

What disease are caused by "exotoxin" release by S. aureus?

Answer 26

1. Toxic shock syndrome 2. Staphylococcal scalded syndrome 3. Gastroenteritis

Question 27

Describe the process of staphylococcal food poisoning

Answer 27

It often occurs after a food handler inoculates food **(usually a _mayonnaise_ containing product),** w/ *S.aureus* that is allowed to incubate at room temp, producing heat-stable _exotoxin_ that causes rapid-onset N/V and abdominal cramping

Question 28

Name the genes involved in each of the (3) steps of the "adenoma-to-carcinoma sequence"

Answer 28

1. **Progression from normal mucosa to a small polyp**: mutation of the _APC tumor suppressor gene_ 2. **Inc. in the size of the polyps**: mutation of the _K-ras protoncogene_ 3. **Malignant transformation**: requires mutation of *both* _p53_ and _DCC_ (Deleted in Colorectal Carcinoma)

Question 29

Name the main organisms that can cause diarrhea with only a small inoculum (4)

Answer 29

1. Shigella 2. Entamoeba histolytica 3. Giardia lamblia 4. Campylobacter jejuni

Question 30

What tumor type(s) is the following tumor marker assc. with?: ## Footnote **Alpha fetoprotein**

Answer 30

- Hepatocellular carcinoma - Germ cell tumors

Question 31

What tumor type(s) is the following tumor marker assc. with?: ## Footnote **CA 19-9**

Answer 31

Pancreatic

Question 32

What tumor type(s) is the following tumor marker assc. with?: ## Footnote **CA 125**

Answer 32

Ovarian

Question 33

What tumor type(s) is the following tumor marker assc. with?: ## Footnote **Carcinoembryonic antigen**

Answer 33

GI (colorectal)

Question 34

What tumor type(s) is the following tumor marker assc. with?: ## Footnote **HCG**

Answer 34

- Choriocarcinoma - Germ cell tumors

Question 35

What tumor type(s) is the following tumor marker assc. with?: ## Footnote **PSA**

Answer 35

Prostate

Question 36

New-onset odynophagia in the setting of chronic GERD usually indicates what? Dx?

Answer 36

Erosive esophagitis and the formation of an ulcer Dx via upper endoscopy

Question 37

Kehr sign

Answer 37

**Referred shoulder pain** due to irritation of the phrenic nerve sensory fibers around the diaphragm as the **result of some abdominal process** (ruptured spleen, peritonitis, hemoperitoneum)

Question 38

*Embryologically*, the dorsal pancreatic bud forms what? The ventral pancreatic bud?

Answer 38

1. _Dorsal_: majority of the pancreatic tissue (body, tail, and most of the head) 2. _Ventral_: precursor of the uncinate process, inferior/posterior portion of the head, and the major pancreatic duct

Question 39

What is pancreas divisum?

Answer 39

Failure of the dorsal and ventral pancreatic buds to fuse

Question 40

_Colonic Diverticula_ 1. Involve what part of the colon? 2. What process leads to their development?

Answer 40

1. Usually involve the sigmoid colon 2. The result of increased intraluminal pressure (**pulsion**) created during strained bowel movements

Question 41

What is the most superficial layer in which you can appreciate an absence of ganglion cells in Hirschsprung dz?

Answer 41

The submucosa of the narrowed area

Question 42

_Bile acid-binding resins_ 1. Give one major example 2. MOA

Answer 42

1. Cholestyramine 2. Binds bile acids, forcing the liver to inc. uptake of LDL in order to create more bile.

Question 43

Describe the relationship between Bile acid-binding resins and Statins

Answer 43

BAB resins (ex. cholestyramine) Inc. stimulation of HMg-CoA Reductase, which will need to be compensated by giving a Statin. Synergistic effects with the statin further reduce plasma LDL level.

Question 44

The (2) most signficant risk factors for development of esophageal SCC in the US

Answer 44

Smoking tobacco and drinking alcohol

Question 45

Presentation of Right-Sided Colon CA

Answer 45

1. Occult bleeding 2. Sx of iron deficient anemia

Question 46

Presentation of Left-sided Colon CA

Answer 46

1. Constipation 2. Sx of Intestinal Obstruction (Left sided colon CA tends to infiltrate the intestinal wall and encircle the lumen)

Question 47

Ulcers in which of these locations are NOT associated with an increased risk of carcinoma in that location? * Duodenum * Esophagus * Stomach * Colon/Rectum

Answer 47

Of these, _only Duodenal ulcers_ are not associated with an inc. risk of CA

Question 48

Which blood vessels does the third part of the duodenum interact with?

Answer 48

It crosses horizontally acros the abdominal aorta and the IVC at the level of L3. The Superior mesenteric vessels lie anterior to the duodenum at this location.

Question 49

Location of femoral hernias

Answer 49

Inferior to the inguinal ligament, lateral to the pubic tubercle, and medial to the femoral vein

Question 50

Presentation/ potential complications of femoral hernias

Answer 50

They can present with groin discomfort or manifest with a bulge on the upper thigh. Incarceration and strangulation are common complications of femoral hernias.

Question 51

_Abetalipoproteinemia_ 1. What is it? 2. Consequence? 3. Describe the histo

Answer 51

1. An inherited **inability to synthesize apoB**, which is critical for chylomicrons and VLDL 2. As a result, _lipids absorbed by the small intestine cannot be transported into the blood_ and accumulate in the intestinal epithelium. 3. Enterocytes w/ clear/ foamy cytoplasm

Question 52

_Achalasia_ 1. Cause 2. What is seen on esophageal manometry?

Answer 52

1. Caused by reduced numbers of inhibitory ganglion cells in the esophageal wall 2. Manometry shows dec. amplitude of peristalsis in the mid esophagus, w/ increased tone and incomplete relaxation at the LES