Gi tract

Enzymes in the digestion of food

1. Gastrin

2. pepsin (active)

3. pepsinogen (inactive)

4. intrinsic factor

Gastrin

secreted from G cells, most potent

Heliobacter pylori breath test

1. H. pylori + urea --> ammonia + CO2

2. Isotopically labeled carbon in a urea compound is given to pt orally

3. Expired CO2 is measure for the labeled carbon atom

Zollinger Ellison syndrome

• gastroma of the pancreas, duodenum, or G cells of stomach

• 60% of cases are malignant

• 25% result in endocrine disorder

• plasma gastrin level >400 ng/L

Normal gastrin level

• Normal plasma gastrin level <100 ng/L

Symptoms of Zollinger Ellison

• Steatorrhea (elevated levels of fecal fat)

• Elevated gastrin levels inhibit the secretion of lipase 

• Watery diarrhea, recurring peptic ulcer, and hyperacidity

Zollinger Ellison differentiation

• Positive = secretin causes gastrin to increase

• Negative = no increase in gastrin or decrease, may indicate hypersecretion problem of G cells

Hypergastrinemia Zollinger Ellison

• Gastric acid secretion greatly increase

• Gastric response to secretin increases

Hypergastrinemia by G cells

• Gastric acid secretion greatly increases

• Gastrin response to secretin normal or decreased

Hypergastrinemia Pernicious anemia

• Gastric acid secretion decreases

  • Gastrin response to secretin decreases

Hypergastrinemia chronic kidney failure

• Gastric acid secretion variable

  • Gastrin response to secretin decreases

Hypergastrinemia Proton pump inhibitor

• Gastric acid secretion decreased

  • Gastrin response to secretin N/A

Pancreas production

1. Insulin

2. Glucagon

3. Pancreatic polypeptide

   1. Other hormones

Pancreatic fluid secretion

• Secretin 

• Cholecystokinin (CCK) 

Secretin 

from small intestine, digestion

Cholecystokinin (CCK)

promotes secretion of pancreatic enzymes, contration of the gall bladder and increase satiety

Secretin/CCK test

direct determination of the exocrine secretory capacity of the pancreas

1. Fast for 6 hours overnight

2. IV administer secretin followed by CCK administration

3. Measure pancreatic enzymes

4. Decrease pancreatic flow = higher enzyme conentrations

   1. Low enzyme conentrations --> Cystic fibrosis, chronic pancreatitis, pancreatic cysts, calcification and edma of pancreas

Disorders of pancreas

1. Assumes at least 10% of pancreatic cells are preserved

2. Severe or advanced disease occurs

   • Glucose intolerance/diabetes mellitus

3. Acute/Chronic pancreatitis

   1. Clinical daignosis marked by increased Amylase or Lipase activity

Acute pancreatitis

1. Excessive alcohol

2. Gallstones

3. Complications from a pancreatography

   1. Idopathic/unknown

Acute pancreatitis less common causes

1. Infection

2. High triglycerides

   1. Hypercalcemia

Amylase

• Also secreted by salivary glands

• acute pancreatitis levels often >10 times the upper range limit

• preferred measurement, specific to pancreas

  • May also see hemalbumin complex in plasma

Amyloclastic

measures decrease in starch substrate

Saccharogenic

measure formation of the product produced from maltose

Chromogenic

measure formation of soluble starch fragments coupled with chromogenic dye

Enzymatic

substrate used in coupled-enzymatic reactions

Lipase LPS

1. Found mainly in pancreas

2. Increased serum levels in acute pancreatitis

3. May be found in perforated peptic ulcers, duodenal ulcers, intestinal obstructions, and cholecystitis

oleic acid emulsion

0.8% + H2O = fatty acid

Chronic pancreatitis

• Ethanol ingestion is main causitive factor

• Likely history of recurrent acute pancreatitis

  • normal or low levels or Amylase/Lipase

Determination of chronic pancreatitis

1. Reduced elastase and chymotrypsin activity from the feces

   1. Fecal fat analysis collected for 3 days

Fecal fat test microscopic

• Stain with Sudan II or Sudan IV

• Search for visible amounts of fat

  • Bind to fat/lipid layer

Fecal fat test quantitative

• Fat is extracted using solvents

• measured by saponification

  • creates separate bilayer

Chronic pancreatitis conditions

1. Malabsorption syndrome

2. obstructive jaundice

3. Crohn's disease

4. cystic fibrosis

5. Whipples disease

6. enteritis

   1. pancreatitis

Pancreatic malignancy

1. Typically, not a primary cancer site, likely metastasized

2. Tumor marker pancreatic cancer CA 19-9

3. unfavorable prognosis

Small intestines

• Majority of absorption in duodenum and jejunum

• Vitamin B12 and bile salts absorbed in the Ileum

Test for gut permeability from stool

1. Calprotectin

2. Lactoferrin

3. Both test elevated with bacterial or viral GI infections

Calprotectin

increased 10 fold in patients with IBS, protein found in white blood cells

Lactoferrin

measurement of white cell protein in feces

Test for carbohydrate absorption

• Xylose absorption - D-xylose measurements in blood and urine at regular intervals

• Lactose tolerance test - lactase and sucrose produced by small intestine

Hydrogen breath tests

dose of non-absorbable carbohydrate or glucose is given

• Bacteria metabolizing the glucose in the gut will give off hydrogen, hydrogen measured in breath test

Disorders of intestines

1. Malabsorption

2. Maldigestion

3. Celiac disease - gluten sensitivity

4. Internal failure - reversible

5. Chronic intestinal failure due to short bowel or Crohn's disease