Small Intestine Flashcards
(132 cards)
Where are 95% of bile acids absorbed?
The terminal ileum. Which absorbs 95% of bile acids through active bile acid transport into the portal circulation. Bile acids circulate back to the liver . Only 5% of bile acids are excreted in stool
What is the main determinant of diarrhea after ileum resection?
The etiology of diarrhea after ileal resection depends on the length of the resected ileum. If less than 100cm of ileum resected, you can see mild bile acid malabsorption but if MRE than 100cm resected you will see SEVERE bile acid malabsorption.
How do the bile acids after ileum resection cause diarrhea?
The unabsorbed bile acids irritate the colonic mucosa resulting in secretory diarrhea (cholerheic diarrhea).
Why does a patient with ileum resection less than 100cm not develop steatorrhea (increase in fat excretion in the stools)?
The liver can compensate for the lost bile acids, and the total bile acid content in the enterohepatic circulation remains constant, therefore steatorrhea does not develop.
what type of treatment is best for patients with (bile acid) diarrhea after ileal resection of less than 100cm?
Bile acid sequestrants ( like cholestyramine)
For which group of patients with ileum resection (Less than 100cm resected vs MORE than 100cm resected) is Bile acid sequestrants ( like cholestyramine) beneficial? and which group is it harmful?
- Beneficial in pts with less than 100cm of ileum resected
- In pts with >100cm resected, cholestyramine will worsen symptoms
Why does a patient with ileum resection MORE than 100cm develop steatorrhea (increase in fat excretion in the stools)?
The liver can NOT compensate for the SIGNIFICANT lost of bile acids, and the total bile acid content in the enterohepatic circulation is DECREASED, leading to fat malabsorption and steatorrhea.
what type of treatment is best for patients with (bile acid) diarrhea after ileal resection more than 100cm?
Treat with low fat diet and anti-diarrheals. Consider medium chain fatty acids
What is meant by the term “ileal break”?
The ileum secretes Peptide YY in response to fat and other luminal nutrients. Peptide YY acts to slow upper GI motility. This negative feedback mechanism is referred to as the ileal break.
How does loss of ileal break contribute to diarrhea after ileal resection?
Losing the ileal break can contribute to diarrhea in patients with ileal resection, because they no longer have the ileum to secrete peptide YY which slows down Upper GI motility.
which clinical syndrome is associated with greasy, foul smelling diarrhea, weight loss, vitamins ADEK deficiencies?
Fat Malabsorption
What are the 3 main causes of fat malabsoprtion?
- Exocrine insufficiency
- Small intestinal disease
- Bile acid deficiency
which two test can be used to prove a patient has fat malabsoprtion?
- Stool Sudan stain (abnormal if > 5fat globules/HPF)
- Fecal fat excretion (abnormal if 7g of fat/24 hours )- patients are told to eat >100g fat per day for the 3 days before the test)
what 4 labs tests can be used to investigate the etiology of fat malabsorption?
- Chem panel to rule out biliary obstruction & look for hepatic disease
- Tissue transglutaminase antibodies (TTG-IgA) for celiac disease
- Fecal elastase to test for pancreatic insufficiency
- D-Xylose test
What types of conditions are suggested by an abnormal vs normal D-xylose test?
- An abnormal D-Xylose test suggests small intestinal mucosal disease
- Normal D-Xylose test suggests pancreatic or other non small bowel cause of steatorrhea.
what are treatment options for fat malabsorption?
Depends on etiology, consider supplementation with medium chain fatty acids, and pancreatic enzyme replacement.
which condition is associated with excessive loss of protein from the GI tract leading to hypoproteinemia and edema?
Protein losing enteropathy
which clinical features include edema, ascites, pericardial or pleural effusion, anasarca, related to the GI tract (not liver)?
Protein losing enteropathy
what are the 2 categories of causes of protein losing enteropathy?
- GI mucosal disease (erosive or non-erosive disease can lead to protein loss form the surface epithelium
- Increased mucosal interstitial pressure due to lymphatic or venous outflow obstruction leading to protein leakage from the mucosa
In terms of GI Mucosal etiologies of protein losing enteropathy, what are the erosive causes?
- Severe gastritis
- Ulcerative jejuno-ileitis
- Infectious colitis/enteritis
- IBD
- GI ischemia
- acute graft vs host
In terms of GI Mucosal etiologies of protein losing enteropathy, what are the NON-erosive causes?
- Hypertrophic gastropathy (Menetriers)
- Celiac disease
- Whipple disease
- Eosinophilic gastroenteritis
- GI sarcoidosis, amyloidosis
In terms of Increased intestinal pressure etiologies of protein losing enteropathy, what are the causes?
- Intestinal lymphangiectasis
- Heart disease (CHF, constrictive pericarditis, etc.)
- Severe portal HTN
- Mesenteric venous thrombosis
- Neoplastic involvement of mesenteric lymph nodes
- Mesenteric tuberculosis
- Retroperitoneal fibrosis
what is the best method to diagnose/evaluate protein losing enteropathy?
Alpha 1 antitrypsin clearance (A1-AT): This is the best way to evaluate enteric protein loss. It requires a 24 hour stool collection because spot measurements are not reliable.
what makes an Alpha 1 antitrypsin clearance test to diagnose/evaluate protein losing enteropathy abnormal?
abnormal If Alpha 1 antitrypsin clearance >27ml/day in patients without diarrhea, and 56ml/day in patients with diarrhea