GI 2 Flashcards
What is a benign metabolism disorder that will present urine samples that are positive for a reducing sugar but negative for glucose?
Essential furctosuria - deficiency of fructokinase
What is an AR characterized by neonatal jaundice, bleeding diathesis, feeding intolerance, and hypotension d/t an absent function of galactose-1-phosphate uridyl transferase?
galactosemia
What enzyme deficiency can cause life-threatening failure to thrive, hepatomegaly, and cirrhosis d/t impaired metabolism of fructose-1-phosphate into dihydroxy acetone phosphate (DHAP) and glyceraldehyde?
aldolase B
What disease presents with hepatomegaly, cardiomegaly, and increased risk for cirrhosis with an acid alpha glucosidase (or acid maltase) deficiency?
Pompe diseae - glycogen storage disease II
What is the most common cause of selective carbohydrate malabsorption with GI Sx of gaseous distention and diarrhea after dairy products?
lactase deficiency
What tumors are composed of nests or sheets of uniform cells with an eosinophilic cytoplasm and oval-to-round stippled nuclei derived from enterochromaffin cells of the intestinal mucosa?
carcinoid tumors
What is distinctive about carcinoid tumors on histology?
minimal to no variation in shape and size of tumor cells
What is characteristic of intestinal carcinoids?
they are malignant transformations of enterochromaffin cells of the intestinal mucosa a part of the amine precursor uptake and decarboxylation (APUD) system
What is the most common location of intestinal carcinoids?
ileum
-also frequently in appendix and rectum
What is a good way to identify the esophagus on CT?
the radiolucency of the air in the trachea can be identified, and the esophagus will be behind it
Describe the Ras-MAP pathway?
a groth factor liganf binds to TK –> autophosphorylation –> phosphotyrosine interacts with many proteins that activates Ras –> activated Ras converts GDP to GTP and begins a phosphorylation cascade with actvation of Raf kinase –> activation of MAP kinase –> enters nucleus to influence gene txn
What does projectile nonbilious vomiting in a newborn with an olive-sized mass in the distal stomach or pyloric region suggest?
pyloric stenosis
What is the cause of pyloric stenosis?
hypertrophy of the pyloric muscularis mucosae - narrowing of pyloric channel is thought to be exacerbated by localized edema and inflammation
what does a Hx of dyspnea and cardiomegaly suggest?
cardiac dysphagia d/t LA enlargement which is is located posteriorly just over the esophagus; increased P in LA can cause distention and pressure on underlying esophagus
When does LA enlargement occur?
in mitral stenosis and LV failure
What is the most common type of malignancy in pts suffering from IBD, particularly ulcerative colitis?
colorectal carcinoma
What are 6 key features that distinguish colitis-associated carcinoma from sporadic colorectal carcinoma?
- affects younger pts
- progress from flat and non-polypoid dysplasia
- hsitologically appear mucinous and/or have signet ring morphology
- develop early p53 mutations and late APC gene mutations (opposite of sporadic)
- be distributed within the proximal colon (esp with Crohn or concurrent primary sclerosing cholangitis)
- be multifocal in nature
When does colorectal carcinoma in IBD pts occur?
after 10y of colitis; tend to be higher grade than sporadic
Explain how colitis-asoociated carcinomas are different from sporadic colorectal carcinomas
more likely to arise from non-polypoid dysplastic lesions, be multifocal in nature, develop early p53 mutations and late APC gene mutations, and be of high histological grade
What are the two arteries given off by the splenic a.? Which is more vulnerable to ischemia after splenic a. blockage?
short gastric aa. and left gastroepiploic a.
-short gastric aa. are more vulnerable to ischemic injury because they have very poor anastomoses, whereas the L gastroepiploic a. has a strong anastomosis with the R gastroepiploic a.
What artery supplies blood to the pylorus and the proximal part of the duodenum?
gastroduodenal a.
What artery supplies blood to the distal lesser curvature of the stomach?
R gastric a.
What artery perfuses the distal greater curvature of the stomach?
R gastroepiploic
What typically causes double-stranded breaks in DNA and what is the repiar mechanism?
exposure to ionizing radiation - repaired by non-homologous end joining
What is PPV?
TP/(TP+FP)
What does dusky red congested vowel with subserosal ecchymoses, edema, and/or well0defined areas of necrosis indicate?
mesenteric ischemia
What is characterized by the preseence of a defect in the intestinal wall along with signs of peritonitis?
intestinal perforation
What is characterized by a dull-appearing peritoneal surface with areas of viscous white-yellow suppurative exudate?
bacterial peritonitis
What is characterized by mesenteric fat that extends along the serosa of an affected segment with dull-gray, edematous, and granular serosa?
Crohn’s disease
What is found on light microscopy in acute interstitial pancreatitis?
focal areas of fat necrosis, calcium deposition, and interstitial edema
What is characterized by chalky-white areas of fat necrosis interspersed with hemorrhage?
necrotizing (hemorrhagic) pancreatitis
What is the MOA of tetrodotoxin?
blocks V0gated Na+ channels in nerve membranes
What is the MOA of verapamil?
blocks L-type calcium channels
What is the MOA of lidocaine?
blocks V-gated Na+ channels in sensory neurons, Purkinje fibers, and ventricular cells
What is the MOA Dofetilide?
class III antiarrhythmic that blocks passive transport of K+, delayed outward rectifier K+ current
How doe parietal cells release H+ ions in the gastric lumen?
by H+/K+ ATPase which requires hydrolysis of ATP
What suppresses activity of gastric parietal cell H/K ATPase? What does this do the pH of the gastric lumen?
PPIs - increase pH of gastric lumen
What is the main site of digestion of dietary lipids?
duodenum
What is the main site of lipid absorption?
jejunum
What kind of chaing is caused by the absence of a gallbladder?
an increase in the rate of enterohepatic circulation as there is no storage place for bile, so it is constantly released into the duodenum
What is the dietary consequence of cholecystectomy?
Pts are less able to tolerate large fatty meals at one sitting because they do not have the ability to release a large amount of stored bile into the gut in a coordinated fashion with meals
Where are most fat-soluble vitamins absorbed?
jejunum
What is the most common cause of infectious esophagitis in HIV pts?
candida albicans
What are the functions of secretin?
it increases bicarbonate production by the pancreas and leads to the secretion of watery alkaline pancreatic juice; it also inhibits gastric acid secretion and stimulates pyloric sphincter contraction
What toxicity presents with GI Sx of H/V, ab pain, diarrhea, decreased consciousness, hypotension, tachycardia, and a garlic odor on the breath?
Arsenic poisoning
What is the Tx of arsenic poisoning?
Dimercaprol - a chelating agent that displaces arsenic ions from teh sulfhydryl groups of hte enzyme
What are the most serious side effects of dimercaprol?
nephrotoxicity and hypertension
What is the chelating agent of choice for acute lead and mercury poisoning?
CaNa2EDTA
What is the treatment of choice for cyanide poisoning and what is the MOA?
amyl nitrate - forms methemoglobin that binds cyanide ions forming the non-toxic compound cyanomethemoglobin thereby preventing cyanide from binding to mitochondrial enzymes in the tissues
What is a chelating agetn used to treat iron poisoning that occurs in pts receiving multiple blood transfusions for conditions such as thalassemia and in pts who consume large amounts of supplemental iron?
Deferoxamine
When does the omphalomesenteric (vitelline) duct normally obliterate?
during the 7th week of embryonic development
What are the rule of 2s in Mecek diverticulum?
2% of the population, 2 ft from ileocecal valve, 2 in. in length, presents in the first 2 years, 2% are symptomatic, maleas are 2x more affected
What explains the two most common Sx in Crohn’s disease of strictures and fistulas?
Transmural inflammation
How are strictures formed in Crohn’s disease?
chronic inflammation causes edema and fibrosis, leading to narrowing of the intestinal lumen, or strictures
How are fistulas formed in Crohn’s disease?
Inflammation and necrosis of the intestinal wall causes ulcer formation. Ulcers can penetrate the entire thickness of the affected intestinal wall, leading to the formation of the fisula
Why are strictures and fistulas not common in ulcerative colitis?
only the mucosa and submucosa are inflamed
What causes toxic megacolon in IBD?
neuromusclar degeneration of the intestinal wall and rapid dilation - associated with bowel perforation
What can aid malabsorption and steatorrhea in CF pts?
pancreatic lipase supplementation
What are the 3 steps and mutations of an “adenoma-to-carcinoma” sequence?
- pregression from normal mucosa to a small polyp: APC tumor suppressor gene mutation
- increase in the size of the polyps: K-ras protooncogene mutation
- Malignant transformation of adenoma into carcinoma: mutation of p53 and DCC
What is the most common appendiceal tumor?
carcinoid tumors
When do you see Sx of carcinoid syndrome?
extraintestinal mets
What is a synthetic analog of GnRH?
Leuprolide
What is Leuprolide used to treat?
prostatic cancer, precocious puberty, and endometriosis
What is an antiandrogen used for the treatment of benign prostatic hyperplasia by inhibiting 5-a-reductase, decreasing formation of DHT?
Finasteride
What is a potent antiemetic used in pts undergoing chemo by selectively blocking 5-HT3 serotonin receptors?
Ondansetron
What is a competitive androgen inhibitor used in the Tx of prostate cancer?
Flutamide
What is the most common location for colon cancer? 2nd most common?
most common: rectosigmoid colon
2nd most common: ascending colon
Colon cancers on what side are smaller, infiltrate the wall of the colon, and more likely to cause obstruction?
left - present with obstructing Sx: altered bowel habits, constipation, ab distension, N/V
Colon cancers on what side are larger, protrude into the colonic lumen, and more likely to bleed?
right
What is the most common GI malignancy?
colon adenocarcinoma
