Diseases of the small bowel Flashcards
4 types of diarrhea
watery, steatorrhea, inflammatory/exudative, functional (IBS)
produced by osmotic gradient change or excessive secretion
watery diarrhea
stool osmotic gap equation
stool osm gap = 290 - 2(stool Na + stool K)
greater than 50 mOsm = osmotic diarrhea
Less than 50 mOsm = secretory diarrhea
Some causes of osmotic diarrhea
lactose intolerance, sorbitol, fructose, Mg-containing laxatives
Some causes of secretory diarrhea
Bacterial toxins (cholera), neuronendocrine tumors (gastrinoma), bile salt, stimulant laxatives, motility disorders (diabetes, IBS)
diarrhea that is fecal fat +
steatorrhea
Causes of steatorrhea
malabsorption (celiac, whipple’s disease, small bowel bacterial overgrowth, short gut from surgery) and maldigestion (pancreatic insufficiency, biliary obstruction)
diarrhea that is often bloody
inflammatory/exudative diarrhea
causes of inflammatory/exudative diarrhea
Crohn’s disease, ischemia, invasive infections (C diff, EHEC, Amebiasis, Shigella)
usually watery diarrhea, diagnosis of exclusion
Irritable Bowel Syndrome
Sx include weight loss, diarrhea, foul-smelling stools and vitamin deficiencies
Eg.: Steatorrhea
malabsorption
Mechanism of pancreatic insufficiency leading to malabsorption
chronic pancreatitis –> pancreatic insufficiency
decreased typsinogen, chymotrypsinogen, proelastase and procarboxypeptidase –> protein malabsorption
decreased lipase and colipase –> lipid maldigestion –> lipid malabsorption
Mechanism of liver disease leading to malabsorption
chronic liver disease (alcoholic cirrhosis, primary biliary cirrhosis, biliary obstruction) –> decreased bile formation –> decreased lipid absorption
Mechanism of Small Intestinal Bacterial Overgrowth (SIBO) leading to malabsorption
stasis (scleroderma, diabetes), partial intestinal obstruction, small bowel diverticula and decreased gastric acid secretion –> bacterial overgrowth –> inactivated bile acids, catabolization of disaccharides, reduced effectiveness of enterokinase –> maldigestion –> eventual deficiency of fat-soluble vitamins A, D, E and B12
differentiate SIBO from tropical sprue
SIBO –> bacterial production of folate; B12 malabsorption –> normal-high folate levels, low B12
tropical sprue –> B12 and folate deficiency
Mechanism of malabsorption in small intestinal structural diseases
damaged mucosa –> decrease in absorptive surface area
unexplained Fe deficiency anemia in adults.
intraepithelial lymphocytes –> loss of villi
Crypt hyperplasia -> malabsorption
+tTg (anti-tissue transglutaminase) IgA
Celiac sprue –> require gluten-free diet
Complication of long-standing celiac disease
T-cell lymphoma
residents/visitors of the tropics. Can occur years after returns from the tropics
patchy villus atrophy
megaloblastic anemia (folate and B12 deficiency) with diarrhea
tropical sprue
infection with G+ Tropheryma whippelii
GI sx, fever, joint pain, or neuro sx
small intestinal biopsy –> blunting, infiltration of lamina propria with large PAS+ staining macrophages filled with organism
Whipple’s disease
treatment of Whipple’s disease
prolonged course of abx
Areas supplied by superior mesenteric artery (SMA)
part of the duodenum, entire small intestine and half of the colon
Areas supplied by the inferior mesenteric artery (IMA)
left colon and rectum
collateral circulation betwen SMA and IMA
marginal arteries and Arc of Riolan
