small bowel diseases Flashcards
When does diarrhea occur?
• When small bowel output exceeds colonic absorptive capacity
What tests do you use with watery diarrhea to get a differential diagnosis?
• Osmotitic vs. secratory • Get the stool osmotic gap • Stool osm gap = 290- 2(stool Na + stool K) ○ If gap> 50mOsm THIS IS OSMOTIC § Lactose intolerance § Sorbitol § Fructose § Magnesium containing laxatives ○ If gap < 50mOsm THIS IS SECRETORY § Bacterial toxins § Neuroendocrine tumors (gastrinoma, VIPoma, Carcinoid § Bile salt (like terminal ileal resection) § Stimulant laxatives § Motility disorders (diabetes, IBS)
What are the 4 different overall types of diarrhea?
- Watery
- Steatorrhea
- Inflammatory/exudative (often bloody)
- Functional (IBS)
What is steatorrhea?
• Fecal fat positive diarrhea • Can be malabsorption OR maldigestion • Malabsorption ○ Celiac ○ Whipple's disease § Whipple diseaseis a systemicdiseasemost likely caused by a gram-positive bacterium, Tropheryma whippelii.[1,2]Although the first descriptions of the disorder described a malabsorption syndrome with small intestine involvement, thediseasealso affects the joints, central nervous system, and cardiovascular system ○ Small bowel bacterial overgrowth ○ Short gut from surgery • Maldigestion • Pancreatic insufficiency • Biliary obstruction
What might cause inflammatory or exudative diarrhea?
• Chrohn's disease • Ischemia • Invasive infections (colon) ○ C difficile ○ EHEC ○ Amebiasis ○ Shigella
When do you classify a watery diarrhea as functional?
- When there is nothing else going on
- This is a diagnosis of exclusion
- Usually watery diarrhea here
- Think IBS
Steatorrhea is a manifestation of what?
• Dysfunctional lipid absorption in some capacity
• Decreased pancreatic and biliary secretions
• Abnormal enterocyte processing
• Lymphatic obstruction
What does Pancreatic Insufficiency have to do with diarrhea?
• Lack of ability to absorb fats and proteins can cause an oily foul-smelling diarrhea called steatorrhea
• steatorrhea occurs because of the decreased activity of lipase and colipase, leading to lipid maldigestions
Describe Small intestinal Bacterial Overgrowth
• There is always normal flora in the proximal small intestine
○ Lactobacilli
○ Enterococci
○ Gram positive aerobes
○ Facultative anaerobes
• Overgrowth occurs in conditions of hypomotility
○ Scleroderma, diabetes
• Partial intestinal obstruction, bowel diverticula and decreased gastric acid secretion also contribute to bacterial overgrowth states.
• Too much bacteria in the lumen means food doesn’t get onto the enterocyte surface
○ Also inactivate bile acids, catabolize disaccharidases in microvilli and reduce effectiveness of enterokinases
• Overgrowth inhibits bowel motility as well
How Liver Disease lead to steatorrhea?
• Fewer hepatocytes and decreased function of the stragglers
• Leads to decreased bile formation
• Bile is necessary for lipid absorption through the forming of micelles.
• No lipid absorption, fatty stools
How might Gastric Disorders cause steatorrhea?
• The bile salts that emulsify the fatty foods get mixed into the chyme in the stomach
• If there is stomach damage or a motility issue that mixing gets less and less efficient, leading eventually to malabsorption of fats
What are the clinical manifestations of small bowel bacterial overgrowth?
• Diarrhea, steatorrhea, abdominal pain, flatulence, bloating and weight loss
• Eventually certain vitamin deficiencies are seen
○ A, D, E and B12
• B12 is because anaerobic bacteria utilize and deplete B12 from the lumen before the enterocytes absorb it
• Serum folate levels are normal or HIGH due to bacterial production of folate
○ One example of an inappropriate normal
○ This is also helpful for ruling out tropical sprue in which B12 and folate deficiency are co-occuring
What are the five categories of disease that can adversely affect and even destroy the absorptive surface area of the small intestine?
• Intestinal inflammation and villus flattening • Ulceration • Ischemia • Infiltration • Other ○ Bypass ○ Extensive small intestine resection
How does celiac sprue ablate the absorptive surface of the small intestine?
• Also known as celiac disease or gluten-sensitive enteropathy
• Inflammatory disease of small intestine, occurring because of an immune response to peptides of gluten
○ Wheat, rye, barley and oats
• Characterized by loss of villi due to the presence of increased intraepithelial lymphocytes
• Also characterized by crypt hyperplasia leading to malabsorption
• It’s the infilration of lymphocytes and the crypt hyperplasia that poof up the villi so much they get flattened out, look like mesas and lose a good portion of their absorptive capacity
How does celiac sprue present clinically?
• Symptoms of malabsorption-steatorrhea
○ Diarrhea, weight loss, bloating and abdominal pain
○ Degree of malabsorption may predict the severity of mucosal involvement
○ Carbohydrate, fat, and protein malabsorption occur because of villus destruction
*ADEK are the fat-soluble vitamin deficiencies
○ Celiac disease affects the proximal small intestine so malabsorption of iron and folate are included
What tests must you order to make the celiac sprue dx?
• Intestinal biopsy ○ See villous flattening, intraepithelial lymphocytes and crypt hyperplasia • Serologic tests ○ anti-endomysial antibodies (IgA) § 90% sensitive, 99% specific ○ Anti-tissue transglutaminases (tTg) § 90% sensitive, 99% specific ○ Anti-gliadin IgA and IgG antibodies § Sensitive, not specific
How do patients manage celiac sprue?
- Lifelong gluten free diet
- Adherence can reverse the villous flattening in weaks
- Also reduces autoantibody titers
