Malabsorption

Question 1

general symptoms of malabsorption

Answer 1

*diarrhea (non-specific)
*steatorrhea (more specific)
*bloating, gas, flatulence
*weight loss > 10% (esp. with increased appetite)

Question 2

specific symptoms of malabsorption

Answer 2

*pica (iron)
*anemia (iron, folate, B12)
*neuropathy (B1, B12)
*night blindness (vitamin A)
*osteoporosis (vitamin D and calcium)

Question 3

causes of disaccharide malabsorption

Answer 3

*lactase deficiency
*fructose intolerance
*sucrase deficiency

Question 4

causes of maldigestion (fat malabsorption)

Answer 4

*gastric resection or bypass
*pancreatic insufficiency
*decreased bile acids (ileal resection/disease, SIBO)

Question 5

causes of global malabsorption (all macronutrients)

Answer 5

*short bowel syndrome
*mucosal disease (Crohn’s, celiac, Whipple’s, amyloidosis, lymphoma, radiation enteritis)

Question 6

lactase deficiency

Answer 6

*most common cause of chronic diarrhea in USA

*primary lactase deficiency:
-absence of the lactase persistence SNP

*secondary lactase deficiency:
-caused by aging, chemo, infections, etc

Question 7

lactase deficiency - diagnosis

Answer 7

*presumptive (ancestry + dairy intake)
*trial of low-lactose or lactose-free diet
*LACTOSE-HYDROGEN BREATH TEST

Question 8

lactase deficiency - treatment

Answer 8

*dietary lactose restriction
*lactase enzyme supplements
*lactase-treated milk

Question 9

sucrase deficiency

Answer 9

*very rare autosomal recessive disorder
*absent gene function
*sx: diarrhea appearing in early infancy
*dx: SUCROSE hydrogen breath test
*Rx: Sucraid; low sucrose diet

Question 10

fructose intolerance

Answer 10

*GLUT5 dysfunction
*not uncommon (increased use of high fructose corn syrup)
*sx: diarrhea after ingestion of fruit and products containing HF corn syrup
*dx: FRUCTOSE hydrogen breath test
*rx: dietary fructose restriction

Question 11

physiologic requisites for fat absorption

Answer 11

*gastric mixing (TG emulsification)
*pancreatic lipase (triglyceride lipolysis -> fatty acids)
*bile salts (fatty acid solubilization in mixed micelles)
*mucosal integrity (fatty acid uptake, re-esterification, export)

Question 12

historical clues for fat maldigestion

Answer 12

*GI surgery (gastric resection or bypass; cholecystectomy; small bowel resection, esp terminal ileum; ulcer operations)
*past episodes of pancreatitis; alcohol abuse
*STEATORRHEA: oil droplets in bowl, greasy toilet ring

Question 13

causes of pancreatic insufficiency

Answer 13

*chronic pancreatitis (common)
*pancreatic cancer with duct obstruction (rare)
*ZE syndrome -> lipase denaturation (very rare)

Question 14

pathophysiology of pancreatic insufficiency

Answer 14

*steatorrhea appears only when pancreatic lipase secretion falls to < 10% of normal
*chronic inflammation leads to alpha & beta cell destruction, causing decreased insulin and glucagon secretion, leading to diabetes
*vitamin B12 malabsorption

Question 15

pancreatic insufficiency - diagnosis

Answer 15

*suspicion
*fecal elastase
*pancreatic imaging by CT, EUS, ERCP

Question 16

pancreatic insufficiency - treatment

Answer 16

*pancreatic enzyme supplements containing lipase at each meal!! (pancrelipase)
*reduced fat diet

Question 17

small intestinal bacterial overgrowth (SIBO) - causes

Answer 17

*achlorhydia (gastrectomy, atrophic gastritis)
*dysmotility (DM, scleroderma)
*ileocecal valve resection
*blind loops (RYGB, jejunal diverticulosis)

Question 18

malabsorption from small intestinal bacterial overgrowth (SIBO) - pathophysiology

Answer 18

*bile acid deconjugation by bacteria -> BA malabsorption -> decreased BA pool -> fat malabsorption
*mixed osmotic/secretory diarrhea
*chronic mucosal inflammation -> villous atrophy -> global malabsorption

Question 19

small intestinal bacterial overgrowth (SIBO) - diagnosis

Answer 19

*suspicion
*jejunal aspiration and quantitative culture (gold standard but not used)
*GLUCOSE-HYDROGEN BREATH TEST (dual peak)

Question 20

small intestinal bacterial overgrowth (SIBO) - treatment

Answer 20

*oral antibiotics
*may require repeat or chronic treatment
*antibiotic rotation to prevent resistance

Question 21

common small bowel mucosal diseases that cause global malabsorption

Answer 21

*celiac disease
*Crohn’s disease
*chronic giardiasis
*short bowel syndrome

Question 22

rare small bowel mucosal diseases that cause global malabsorption

Answer 22

*eosinophilic gastroenteritis
*Whipple’s disease
*intestinal amyloidosis
*intestinal lymphoma
*abetalipoproteinemia
*lymphangectasia