Lipid Malabsorption Clinical Concepts Flashcards
Intestinal permeability test
- D-xylose
- small-bowel follow-through
Malabsorption refers to:
It can result from:
impaired absorption of nutrients
- It can result from
- congenital defects in the membrane transport systems of the small intestinal epithelium (primary malabsorption)
- acquired defects in the epithelial absorptive surface (secondary malabsorption).
- maldigestion, impaired digestion of nutrients within the intestinal lumen
- Although malabsorption and maldigestion are pathophysiologically different, the term malabsorption has come to denote derangements in both processes.
Digestion and absorption of fat involve a complex mechanism.
It requires:
- bile acids
- digestive enzymes
- a normally functioning small intestinal mucosa
Dietary lipids, mostly as triacylglycerols, are initially _________and then __________into free fatty acids and monoglycerides
emulsified by bile acids; hydrolyzed by the pancreatic lipases and colipases
In the proximal small bowel, hydrolyzed lipids form ______by the action of bile acids
which are then absorbed across the _________ and transported as ______ via the _________
- micelles
- intestinal villi; chylomicrons; intestinal lymphatics
The causes of steatorrhea are numerous and subclassify under three broad categories:
- conditions leading to Exocrine Pancreatic insufficiency (EPI)
- bile acid deficiency states, and
- diseases affecting the small intestine.
EPI due to:
- chronic pancreatitis,
- cystic fibrosis (CF),
- and conditions resulting in pancreatic duct obstruction or resection of the pancreas (e.g., pancreatic tumors)
Bile acid deficiency either due to:
- cholestasis (e.g. primary biliary cholangitis (PBC),
- primary sclerosing cholangitis (PSC))
- ileal resection or Crohn disease of the ileum
- deconjugation of bile acids (e.g., small intestinal bacterial overgrowth (SIBO))
Diseases affecting proximal small intestines such as:
- celiac disease
- tropical sprue
- giardiasis
- Whipple disease
- lymphoma
- amyloidosis
- SIBO
- and HIV enteropathy
Steatorrhea is one of the clinical features of fat malabsorption and noted in many conditions such as
- exocrine pancreatic insufficiency (EPI)
- celiac disease
- tropical sprue.
An increase in the fat content of stools results in the production of
pale, large volume, malodorous, loose stools
Screening for steatorrhea may be carried out by
examining stool samples for the presence of fat by Sudan III staining
quantitative fecal fat estimation is required to confirm the diagnosis
Fat malabsorption causes symptoms therefore the history often allows you to diagnose this problem
- Foul smelling stools
- Oil in stool (oil droplets)
- Mild to moderate diarrhea
- history of intestinal resection
- History of pancreatitis
•OIL IS NOT WHITE (MUCUS)
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Test for Fat Malabsorption
Stool Fat
Qualatative test:
Quantitative test:
- Qualitative test
- Sudan stain
- Quantitative test
- measure > 6 grams of fat per day in a stool specimen from a patient eating 100 grams of fat per day (72 hour collection)
Pancreatic Insufficiency Tests
- The secretin stimulation test
- secretin causes the secretion of bicarbonate-rich fluid from the pancreas.
- Fecal elastase
- overall sensitivity and specificity of 93 percent for pancreatic insufficiency
- Among pancreatic function tests, fecal elastase measurement is the most sensitive and specific in the early phases of pancreatic insufficiency.
- Fecal chymotrypsin is easy to measure and levels are stable in stool samples for days.
- levels are usually elevated only in advanced pancreatic disease. As a result, the overall sensitivity for pancreatic insufficiency is only approximately 50 to 60 percent.
Intestinal permeability tests
- D-xylose
- small-bowel follow-through
are neither specific nor sensitive and are not recommended for CD diagnosis.
Jejunal Resection vs Ileal Resection
Absorption:
Vitamin and Bile salts absorption:
Adaptation:
Transit:
- Jejunal
- adequate absorption unless >75% resected
- Preserved absorption of B12 and bile salts
- Good ileal adaptation
- Normal transit
- Ileal
- Adequate calorie and fluid absorption
- Malabsorption of
- bile salts
- vitamin B12
- Poor jejunal adaptation
- Rapid intestinal transit
Bile acids are absorbed only in the terminal ileum. Resection of ______ of ileum loses some bile salts to the colon where they act as laxatives. The liver increases the synthesis to maintain a normal bile salt pool size. It cannot compensate for a greater resection. Less bile salt leads to ________.
<100cm
maldigestion and steatorrhea
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Treatment
Malabsorption:
Maldigestion:
- Malabsorption
- Treat the underlying intestinal disease
- Maldigestion
- Supplemental enzymes that contain lipases
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Small Intestinal Diseases
- Celiac Disease
- Tropical Sprue
- Whipple’s Disease
- Bacterial Overgrowth