GI Flashcards
Linkage disequilibrium
When a pair of alleles are inherited together in the same gamete (haplotype) more or less often than would be expected given random chance
Gallstone ileus
- What is it?
- Presentation
- Dx
- Obstruction in the ileum due to passage of a large gallstone through a cholecystenteric fistula in the small bowel
- SBO
- Dx: Ab XR may reveal gas within the gallbladder and biliary tree
Positive Predictive Value
The proportion of indivudals with positive test results who actually have the dz
PPV = TP/ (TP + FP)
Between positive/ negative predicative values, and sensitivity/ specificty, which are dependent on disease prevalence in the tested population?
Positive/ negative predictive values
Enteropeptidase
- What secretes it?
- What does it do?
- What does its deficiency lead to?
- Comes from the jejunal brush border
- Activates trypsin from trypsinogen (needed for peptide breakdown and activation of other pancreatic enzymes)
- Deficiency impairs protein and fat absorption
Where are dietary lipids digested? Where are they absorbed?
- Digestion: in the duodenum via pancreatic enzymes
- Absorbed: in the jejunum in the form of water-soluble micelles
What type of MHC do APCs express?
MHC Class II so that they can present antigen to CD4 cells
Inherited defects involving what signaling pathway, result in disseminated mycobacterial dz in infancy/ early childhood?
Interferon-gamma
(needed to activate macrophages)
Where does the gastroduodenal artery sit? How can it be affected by ulceration?
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.
Meckel diverticulum
- What is it/ How common is it?
- What causes it?
- The most common congenital anomaly of the small intestine
- It forms due to incomplete obliteration of the omphalomesenteric duct that connects the midgut lumen and yolk sac cavity
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?
Gastric (most common), pancreatic, colonic, endometrial, small bowell, etc.
This is an example of ectopy
Presentation of Meckel diverticulum
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.
- What is the cause of umbilical hernias?
- What conditions are they associated with?
- Incomplete closure of the umbilical ring
- Dat Big Hernia –> assc. w/ Down Syndrome, Beckwith-Wiedmann syndrome, Hypothyroidism
What type of polyps are most likely to undergo malignant transformation?
Villous adenomas
Vitamin E deficiency
- Who does it occur in?
- What is defiency in this vitamin associated with?
- Clinical manifestations
- Can occur in individuals with fat malabsorption
- Assc. w/ inc. susceptibility of the neuronal and erythrocyte membranes to oxidative stress
- Clinical manifestations: ataxia, impaired proprioception and vibratory sensation, and hemolytic anemia
Normal Vitamin E function
Protection of fatty acids against oxidation
What type of drug is useful for nausea assc. with GI insults?
For nausea assc. with migraine?
GI: 5-HT3 receptor antagonists
Migraine: Dopamine antagonists
What is the best non-surgical tx for cholesterol gallstones?
Hydrophilic bile acids (eg ursodeoxycholic acid). These decrease biliary cholesterol secretion and increase biliary bile acid concentration, improving cholesterol solubulity.
How is Campylobacter infection spread?
Via domestic animals or from contaminated food
Inapparopriate activation of what enzyme, leads to pancreatitis?
Trypsinogen (to trypsin)
- Pernicious anemia (Vit B12 def.) is caused by autoimmune destruction of what cells?
- What do these cells secrete and where are they located?
- Destruction of parietal cells (chronic atrophic gastritis).
- They secrete HCL and IF, and are found primarily in the superficial region of the gastric glands
What are the (3) tx for C.diff and in what situation would you use each?
- Metronidazole (Initial mild/moderate C. Diff tx)
- Vancomycin (Severe or recurrent C. Diff)
- Fidaxomicin (recurrent C. Diff and inc. risk of recurrence)
The venous component of internal hemorrhoids drain where?
External hemorrhoids?
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
Primary Biliary Cirrhosis/ Cholangitis
- What characterizes this dz?
- Who is it common in ?
- Presentation?
- Chronic liver dz characterized by autoimmune destruction of the intrahepatic bile ducts and cholestasis (elevated alk phos)
- Most common in middle aged women
- Sx: Severe pruritis (especially at night)
What is the main dz Primary Biliary Cirrhosis (PBC) is associated with?
Sjrogren’s syndrome (and other autoimmune disorders)
What disease are caused by “exotoxin” release by S. aureus?
- Toxic shock syndrome
- Staphylococcal scalded syndrome
- Gastroenteritis
Describe the process of staphylococcal food poisoning
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
Name the genes involved in each of the (3) steps of the “adenoma-to-carcinoma sequence”
- Progression from normal mucosa to a small polyp: mutation of the APC tumor suppressor gene
- Inc. in the size of the polyps: mutation of the K-ras protoncogene
- Malignant transformation: requires mutation of both p53 and DCC (Deleted in Colorectal Carcinoma)
Name the main organisms that can cause diarrhea with only a small inoculum (4)
- Shigella
- Entamoeba histolytica
- Giardia lamblia
- Campylobacter jejuni
What tumor type(s) is the following tumor marker assc. with?:
Alpha fetoprotein
- Hepatocellular carcinoma
- Germ cell tumors
What tumor type(s) is the following tumor marker assc. with?:
CA 19-9
Pancreatic
What tumor type(s) is the following tumor marker assc. with?:
CA 125
Ovarian
What tumor type(s) is the following tumor marker assc. with?:
Carcinoembryonic antigen
GI (colorectal)
What tumor type(s) is the following tumor marker assc. with?:
HCG
- Choriocarcinoma
- Germ cell tumors
What tumor type(s) is the following tumor marker assc. with?:
PSA
Prostate
New-onset odynophagia in the setting of chronic GERD usually indicates what?
Dx?
Erosive esophagitis and the formation of an ulcer
Dx via upper endoscopy
Kehr sign
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)
Embryologically, the dorsal pancreatic bud forms what?
The ventral pancreatic bud?
- Dorsal: majority of the pancreatic tissue (body, tail, and most of the head)
- Ventral: precursor of the uncinate process, inferior/posterior portion of the head, and the major pancreatic duct
What is pancreas divisum?
Failure of the dorsal and ventral pancreatic buds to fuse
Colonic Diverticula
- Involve what part of the colon?
- What process leads to their development?
- Usually involve the sigmoid colon
- The result of increased intraluminal pressure (pulsion) created during strained bowel movements
What is the most superficial layer in which you can appreciate an absence of ganglion cells in Hirschsprung dz?
The submucosa of the narrowed area
Bile acid-binding resins
- Give one major example
- MOA
- Cholestyramine
- Binds bile acids, forcing the liver to inc. uptake of LDL in order to create more bile.
Describe the relationship between Bile acid-binding resins and Statins
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.
The (2) most signficant risk factors for development of esophageal SCC in the US
Smoking tobacco and drinking alcohol
Presentation of Right-Sided Colon CA
- Occult bleeding
- Sx of iron deficient anemia
Presentation of Left-sided Colon CA
- Constipation
- Sx of Intestinal Obstruction
(Left sided colon CA tends to infiltrate the intestinal wall and encircle the lumen)
Ulcers in which of these locations are NOT associated with an increased risk of carcinoma in that location?
- Duodenum
- Esophagus
- Stomach
- Colon/Rectum
Of these, only Duodenal ulcers are not associated with an inc. risk of CA
Which blood vessels does the third part of the duodenum interact with?
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.
Location of femoral hernias
Inferior to the inguinal ligament, lateral to the pubic tubercle, and medial to the femoral vein
Presentation/ potential complications of femoral hernias
They can present with groin discomfort or manifest with a bulge on the upper thigh.
Incarceration and strangulation are common complications of femoral hernias.
Abetalipoproteinemia
- What is it?
- Consequence?
- Describe the histo
- An inherited inability to synthesize apoB, which is critical for chylomicrons and VLDL
- As a result, lipids absorbed by the small intestine cannot be transported into the blood and accumulate in the intestinal epithelium.
- Enterocytes w/ clear/ foamy cytoplasm
Achalasia
- Cause
- What is seen on esophageal manometry?
- Caused by reduced numbers of inhibitory ganglion cells in the esophageal wall
- Manometry shows dec. amplitude of peristalsis in the mid esophagus, w/ increased tone and incomplete relaxation at the LES
