General GI Flashcards
(277 cards)
Acid ingestions versus basic cause what type of necrosis?
Acid: coagulation necrosis
Basic: liquefaction necrosis –> 1000 fold lifetime risk for developing esophageal CA
Meds that affect tacrolimus level
Increase level: Azole antifungals, calcium channel blockers, and macrolides inhibit the P450 system
Decrease level: Antiseizure agents (such as dilantin) and anti-TB agents can induce the P450 system
Metoclopramide MOA
Inhibition of D2 and 5-HT3-> anti-emetic effcts
Stimulation of 5-HT4 with release of Ach->prokinetic effects
Reye’s Syndrome
Reye’s syndrome involves mitochondrial defects in fatty acid oxidation, caused by a double insult of viral infection (flu, gastroenteritis) and mitochondrial toxins (i.e. salicylates). It is best characterized as an event occurring after aspirin is given for a viral illness, and presents as vomiting/lethargy followed by encephalopathy and hepatocyte damage (ALT and AST 3X > normal). Liver biopsies show microvesicular steatosis without necrosis, and electron microscopy shows mitochondrial changes. Bilirubin levels are usually normal or only slightly increased, and if cholestasis is present other diagnoses should also be considered.
What is the most sensitive indicator for renal cyclosporine toxicity? A. cyclosporine level B. blood pressure C. GFR calculated using creatinine D. Creatinine E. GFR based on inulin
E
Cyclosporine binds with cyclophilin, which in turn inhibits calcineurin. Active calcineurin normally dephosphorylates nuclear factor of activated T cells (NFAT-1), allowing it to enter the nucleus and promote transcription of IL-2 and other pro-T and B cell cytokines. Hence, cyclosporine is known as a calcineurin inhibitor (Tacrolimus works in a similar way, binding to its partner FK-506 binding protein to inhibit calcineurin).
Cyclosporine causes two forms of renal toxicity: acute and chronic. Acute toxicity is characterized by afferent and efferent arteriole vasoconstriction, secondary to endothelial cell dysfunction. This results in a drop in GFR and acute renal failure. Chronic toxicity occurs from vasoconstriction leading to ischemia and structural changes in the kidneys. Acute toxicity is reversible by withdrawing the medication, whereas chronic toxicity is thought to be permanent.
Clinically, patients with cyclosporine toxicity present with decreased GFR. They have hypertension secondary to sodium/volume retention, as the kidneys try to preserve perfusion in the setting of arteriole constriction. The lowered GFR also leads to an increase in BUN and creatinine. Hence, the most sensitive test to determine toxicity would be one that identifies an impaired GFR. Inulin, an inert substance that is freely filtered through the glomerulus and not reabsorbed, is used to accurately determine GFR.
A 7 month old infant is brought to you for evaluation because of recurrent vomiting and lethargy for 3 months. Dietary history reveals that she was exclusively breastfed until 5 months and her diet now consists of cereal, fruits, fruit juice, and vegetables. What enzyme deficiency is likely? A. fructose-6-phosphate B. triokinase C. aldolase B D. lactase E. sucrase isomaltase
c Aldolase B
This patient tolerates lactose from breast milk but does not tolerate foods with sucrose/fructose (lactose is a disaccharide made from glucose and galactose, whereas sucrose is a disaccharide made from glucose and fructose). Sucrose is digested by the brush border enzyme complex sucrose isomaltase, which has both sucrase and alpha1,6 dextrin hydrolyzing activity. Deficiencies in this enzyme result in sugar malabsorption and diarrhea.
Fructose, once transported into the enterocytes by facilitate diffusion, becomes phosphorylated to fructose-1-phosphate by fructokinase. Aldolase B then controls the fate of the molecule, cleaving it into products that enter the glycolytic, gluconeogenic, or glycogen synthesis pathways. Without this enzyme, fructose-1-phosphate accumulates. Such patients with hereditary fructose intolerance develop poor feeding, vomiting, lethargy, hypoglycemia, failure
Cobalamin (Vitamin B12) absorption may be impaired in each of the following conditions EXCEPT: A. pernicious anemia B. cholestatic jaundice C. Crohn’s ileitis D. Zollinger-Ellison syndrome E. Small bowel bacterial overgrowth F. Pancreatic insufficiency
B. Vitamin B12 (cobalamin) comes mainly from the cobalamin-containing meats, but gut bacteria produce small amounts that are absorbed. The absorption of B12 from foodstuffs is a well-characterized process. First, cobalamin must make it through the acidic stomach, by binding to haptocorrin (R binder) at low pH. Most of the gastric haptocorrin originates from saliva. In the duodenum, pancreatic proteases activate in the presence of bicarbonate, hydrolyze haptocorrin, and liberate cobalamin. The cobalamin in turn binds to intrinsic factor (made by gastric parietal cells) and becomes resistant to pancreatic proteases. The cobalamin/intrinsic factor complex binds to an ileal brush border receptor and enters enterocytes. Given this sequence, B12 absorption can be impaired at multiple steps. Pernicious anemia leads to low intrinsic factor, due to autoimmune attack on parietal cells. Zollinger-Ellison syndrome causes the duodenum to be too acidic, preventing protease activation and degradation of the haptocorrin/cobalamin complex. In the same way, pancreatic insufficiency prevents degradation of haptocorrin/cobalamin. Bacterial overgrowth in the small intestine disrupts the cobalamin/intrinsic factor interaction, and ileal disease affects cobalamin/intrinsic factor binding at the ileal brush border. Cholestasis does not alter B12 absorption. Bile does contain haptocorrin, but salivary haptocorrin is clinically the most important.
Which of the following is not a recognized disease association of hepatitis C viral infection?
A. Cryoglobulinemia
B. Porphyria cutanea tarda
C. Membranoproliferative glomerulonephritis
D. Diabetes mellitus
E. Increased risk of myocardial infarction
E.
There are many extrahepatic manifestations of Hepatitis C. Cryoglobulinemia occurs when Hepatitis C-antibody complexes form in the blood. “Mixed” cryoglobulinemia refers to complexes with IgG against the Hepatitis C antigen and IgM against the IgG. To diagnose cryoglobulinemia, blood samples must be kept warm because the complexes precipitate when cooled.
Porphyria cutanea tarda is a common skin manifestation of Hepatitis C. As a result of liver dysfunction, the UROD gene (uroporphyrinogen decarboxylase) is impaired, heme synthesis is halted, and porphyrins build up. The porphyrins collect in the skin absorb visible violet light, producing free radicals that damage nearby tissue. In the skin, the most common findings are erosions, blisters, and scarring.
Membranoproliferative glomerulonephritis is also seen with Heptitis C, perhaps from a vasculitis produced by the antibody-antigen complexes. Diabetes mellitus (adult-onset, insulin resistant) is 4X more likely in Hepatitis C patients for unknown reasons. Some have speculated that the antibody response induced by Hepatitis C results in an autoimmune attack of the pancreas. No association between Hepatitis C and myocardial infarction has been demonstrated.
Sorbitol ingestion
Soft drinks and sugar free gum
Can cause persistent, osmotic diarrhea. Abdominal pain and bloating
DNA hepatitis virus
HBV
Hepatitis virus-RNA and without envelope
HEV and HAV
HEV transmission
When is it most dangerous?
spread through contaminated water. Most dangerous during pregnancy
Pancreatitis genes
CFTR, PRSS1, CTC1, SPINK 1
sTIMULANTS OF ACID
Gastrin, Histamine, Ach
Hirschprungs Disease stain
AchE
HD gene and its association
Ret gene
Ret also assc with MEN2B
Delayed Gastric emptying
> 90% at 1 hr
60% at 3 hrs
10% at 4 hrs
Rapid gastric emptying
retained meal <30% at 1 hr
Alagille
ductopenia (<8 ducts per portal tract) paucity of interlobular bile ducts cholestasis 2/2impaired micelle formation JAG1/NOTCH 2 pulmonic stenosis
Lactose breath test indicative of lactose malabsorption
increase in H by 20 ppm in >3 hrs is positive or failure of blood sugar to rise to 20 by 30 min after ingestion
breath test for SIBO
Rise for than 20 in <90 min
toxic megacolon
transverse colon > 56 mm
Normal sensation for ARM
30-40 mL
Normal Urge for ARM
90-110 mL