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GIR Test 4 > B5.072 Malabsorption Syndrome > Flashcards

B5.072 Malabsorption Syndrome Flashcards

1
Q

malabsorption syndrome

A

diminished intestinal absorption of one or more nutrients

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2
Q

steatorrhea

A

an increase in stool fat excretion to >6% of dietary fat intake

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3
Q

osmotic diarrhea

A

diarrhea secondary to diminished absorption of one or more dietary nutrients
ceases during fasting

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4
Q

secretory diarrhea

A

diarrhea due to small and/or large intestinal fluid and electrolyte secretion
associated with enterotoxins
unaffected by fasting

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5
Q

how can bile acid defects contribute to steatorrhea

A

defects in any of the steps in enterohepatic circulation of bile acids can result in a decrease in the duodenal concentration of the conjugated bile acids and consequently in the development of steatorrhea

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6
Q

steps in enterohepatic circulation of bile acids that can go awry

A
  1. decreased synthesis
  2. decreased biliary secretion
  3. maintenance of conjugated bile acids
  4. decrease in reabsorption
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7
Q

defect causing decreased bile acid synthesis

A

decreased hepatic function

ex: cirrhosis

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8
Q

defect causing decreased biliary secretion of bile acids

A

defective canalicular excretion of organic anions, including bile acids
ex: PBC

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9
Q

defect causing impaired maintenance of conjugated bile acids

A

bacterial overgrowth in the small intestine results in decrease in conjugated bile acids below the critical micellar concentration (CMC)
ex: jejunal diverticulosis

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10
Q

why cant unconjugated bile acids form micelles?

A

quickly absorbed

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11
Q

defect causing decrease in reabsorption of bile acids

A

increase in delivery of bile acids to the large intestines

ex: ileal dysfunction caused by Crohns or surgical resection

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12
Q

what is choleretic enteropathy

A

bile acid diarrhea

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13
Q

discuss bile acid diarrhea (choleretic enteropathy)

A

limited ileal disease causing reduced bile acid absorption
fecal bile acid secretion COMPENSATED by extra hepatic synthesis
mild to no steatorrhea bc extra hepatic synthesis is compensating

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14
Q

treatment for bile acid diarrhea

A

cholestyramine

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15
Q

discuss the pathophys of fatty acid diarrhea

A

extensive ileal disease leading to reduced bile acid absorption
fecal bile acid loss NOT COMPENSATED by hepatic synthesis
reduced bile acid pool size; intraduodenal concentration of bile acids is reduced to less than the CMC
>20 g steatorrhea

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16
Q

treatment of fatty acid diarrhea

A

low fat diet

cholestyramine many not be effective and may further exacerbate the problem

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17
Q

3 types of fatty acids in fats

A

LCFAs
MCFAs
SCFAs

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18
Q

dietary fat compositions

A

long chain triglycerides (LCTs)

glycerol bound via ester linkages to 3 LCFAs

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19
Q

3 integrated processes that assimilate dietary lipids

A
  1. an intraluminal/digestive phase
  2. mucosal/absorptive phase
  3. delivery/post-absorptive phase
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20
Q

pathophysiological defects in lipolysis

A
  1. decreased pancreatic lipase secretion down to 5% or lower
  2. reduction in intraduodenal pH (pancreatic lipase inactivated below 7)
  3. decrease in pancreatic bicarb secretion for same reason as above
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21
Q

disease that can lead to defects in lipolysis

A

chronic pancreatitis

CF

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22
Q

pathophysiological defect in mucosal uptake

A

steatorrhea can result from impaired movement of mixed micelles across the unstirred aqueous fluid layer if the relative thickness of the unstirred water layer increases
ex: celiac, bacterial overgrowth syndrome

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23
Q

what is abetalipoproteinemia

A

impaired synthesis of B lipoproteins
deficiency in chylomicron formation leads to lipid laden small intestinal epithelial cells that before normal in appearance after fasting
disorder associated with abnormal erythrocytes, neuro problems, and steatorrhea

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24
Q

what is intestinal lymphangiectasia

A

abnormal intestinal lymphatics

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25
MCT digestion
do not require lipolysis and can be absorbed intact by intestinal epithelial cells no micelle formation necessary
26
SCFAs
not dietary lipids synthesized by colonic bacterial enzymes from nonabsorbed carbohydrates rapidly absorbed and stimulate colonic NaCl and fluid absorption
27
cause of antibiotic associated diarrhea
antibiotic suppression of the colonic microbiota with a resulting decrease in SCFA production
28
forms of carbohydrates in diet
starch disaccharides (sucrose + lactose) glucose
29
big picture absorption of carbohydrates
only absorbed in small intestine and only in the form of monosaccharides
30
clinically important disorder of carbohydrate absorption
lactose malabsorbtion
31
how is lactose digested
brush border lactase | broken down into glucose and galactose which can be transported into cells via SGLT
32
primary lactase deficiency
genetically determined decrease or absence of lactase all other aspects of both intestinal absorption and brush border enzymes are normal common in adulthood
33
secondary lactase deficiency
caused by diseases that destroy the lining of the small intestine along with lactase seen in celiac, crohns, UC, chemo, and long courses of antibiotics
34
symptoms of lactose malabsorption
diarrhea abdominal pain cramps flatus
35
pathology often confused with lactase deficiency
IBS | persistence of symptoms in an individual who exhibits lactose intolerance while on a lactose free diet suggests IBS
36
factors that may play into severity of symptoms related to lactose intolerance
1. amount of lactose in diet 2. rate of gastric emptying (faster=worse) 3. small intestine transit time (faster=worse) 4. colonic compensation by production of SCFAs from nonabsorbable lactose (reduced microflora=increased symptoms)
37
glucose and galactose malabsorption
congenital absence of SGLT1 | diarrhea with glucose and galactose but not with fructose
38
protein digestion and absorption
present in food as polypeptides and broken down into di- and tri-peptides absorbed by separate transport systems for di and tripeptides and for different types of AAs (nonpolar and dibasic)
39
enterokinase deficiency
absence of enterokinase which converts trypsinogen to trypsin associated with diarrhea, growth retardation, and hypoproteinemia
40
Hartnup's syndrome
defect in transport of nonpolar AAs | pellagra like rash and neuropsychiatric symptoms
41
cystinuria
defect in dibasic AA transport | associated with renal calculi and chronic pancreatitis
42
clinical picture of short bowel syndrome
symptoms of malabsorption | recent small intestinal resection for mesenteric ischemia
43
gold standard for establishing diagnosis of steatorrhea
quantitative stool fat determination
44
Sudan II staining
qualitative stool fat test | rapid and inexpensive but not as good as qualitative test
45
vitamins that may be deficient in cases of steatorrhea
A, D, E, K
46
vitamin D malabsorption symptoms
metabolic bone disease elevated alk phos reduced serum calcium
47
vitamin K deficiency findings
elevated PT without liver disease or anticoagulants
48
macrocytic anemia
evaluate for cobalamin or folic acid malabsorption
49
iron deficiency anemia without occult bleeding
evaluate for iron malabsorption | exclude celiacs
50
where is iron absorbed
proximal small intestine
51
the schilling test
test to determine the cause of cobalamin malabsorption
52
urinary d-xylose test
test for carbohydrate absorption provides assessment of proximal small intestine mucosal function administer 25 g or d-xylose and collect urine for 5 h, excreting < 4.5 g reflects duodenal/ jejunal disease
53
what findings may be illuminated on small intestine radiologic examination
``` intestinal dilation w extensive mucosal disease anatomic abnormalities (crohns, blind loop) ```
54
indications for a small intestine biopsy
1. documented or suspected steatorrhea or chronic diarrhea | 2. diffuse or focal abnormalities of the small intestine defined on a small intestinal series
55
categories of lesions on a small intestine biopsy
1. diffuse, specific 2. patchy, specific 3. diffuse, nonspecific
56
diseases associated with diffuse, specific lesions on SI biposy
whipples disease agammaglobulinemia abetalipoproteinemia
57
diseases associated with patchy, specific lesions on SI biopsy
``` intestinal lymphoma intestinal lymphangiectasia eosinophilic gastroenteritis amyloidosis crohns infections mastocytosis ```
58
diseases associated with diffuse, nonspecific lesions on SI biopsy
``` celiac tropical sprue bacterial overgrowth folate deficiency vitamin B12 deficiency radiation enteritis Zollinger-Ellison syndrome protein calorie malnutrition drug induced enteritis ```
59
pathologic findings with whipples disease
lamina propria includes macrophages containing material positive on periodic acid Schiff staining
60
pathologic findings with agammaglobulinemia
absence of plasma cells flat mucosa often patients have a giardia infection
61
pathologic findings with abetalipoproteinemia
normal villi | epithelial cells vacuolated with fat postprandially
62
pathologic findings in intestinal lymphangiectasia
dilated lymphatics | clubbed villi
63
pathologic findings in celiac
short or absent villi mononuclear infiltrate epithelial cell damage hypertrophy of crypts
64
test for pancreatic exocrine function
secretin test | measures pancreatic secretions by duodenal intubation following IV admin of secretin
65
test results in chronic pancreatitis
d-xylose = normal Schilling = 50% abnormal, if abnormal use pancreatic enzyme treatment duodenal mucosal biopsy = normal
66
test results in bacterial overgrowth syndromes
d-xylose = normal or modestly abnormal Schilling = often abnormal, treat w antibiotics duodenal mucosal biopsy = usually normal
67
test results in ileal disease
d-xylose = normal Schilling = abnormal duodenal mucosal biopsy = normal
68
test results in celiac
d-xylose = decreased Schilling = normal duodenal mucosal biopsy = flat
69
test results in intestinal lymphangiectasia
``` d-xylose = normal Schilling = normal biopsy = dilated lymphatics ```
70
what is celiac disease
autoimmune disorder affecting small intestine caused by a reaction to gluten common cause of malabsorption
71
symptomatic presentations of celiac disease
1. small number have classical symptoms 2. much larger number have atypical presentation (anemia, infertility neuro symptoms) 3. some are symptomatic despite histo abnormalities
72
hallmark of celiac
abnormal small intestinal biopsy and response to the elimination of gluten from the diet
73
distribution of severity in celiac
proximal to distal | reflects exposure of intestine to varied amounts of dietary gluten
74
when might symptoms of celiac appear?
1. intro of cereals into an infant's diet | 2. any age throughout adulthood w frequent spontaneous remissions or exacerbations
75
celiac serologies
IgA antigliadin, anti-tTG , and antendomysial antibodies
76
genetics factors in celiac
HLA-DQ2,8
77
how to diagnose celiac
histo changes on small intestine biopsy with improvement after initiation of gluten free diet
78
what % of patients w celiac respond to complete gluten restriction
90%
79
outcomes of refractory celiac disease (does not respond to gluten free diet)
1. respond to restriction of other dietary protein (soy) 2. respond to glucocorticoid treatment 3. temporary symptoms 4. fail to respond to all measures and have a fatal outcome w complications like intestinal T cell lymphoma or autoimmune enteropathy
80
mechanisms of diarrhea in celiac
1. steatorrhea from changes in jejunal mucosal function 2. secondary lactase deficiency due to changes in jejunal brush border enzymatic function 3. bile acid malabsorption (in cases with ileal involvement) 4. endogenous fluid secretion from crypt hyperplasia
81
diseases associated w celiac
``` dermatitis herpetiformis (DH) DM1 IgA def down syndrome turner's syndrome ```
82
complications of celiac
``` most important: cancer -GI and nonGI neoplasms -intestinal lymphoma intestinal ulceration independent of lymphoma iron deficiency anemia ```
83
what is short bowel syndrome
clinical problems that follow resection of various lengths of small intestine rarely congenital
84
situations that mandate intestinal resection
1. mesenteric vascular disease 2. primary mucosal and submucosal disease (crohns) 3. traumas
85
how does removal of the ileum impact diarrhea
more severe diarrhea than jejunal resection can cause diarrhea by an increase in bile acids entering the colon stimulating secretions absence of ileocecal valve is associated with decrease in intestinal transit time and bacterial overgrowth from the colon
86
nonintestinal symptoms of short bowel syndrome
1. increased frequency of renal calcium oxalate calculi 2. increase in cholesterol gallstones related to a decrease in bile acid pool size 3. gastric hypersecretion due to reduced hormonal inhibition of acid secretion or increased gastrin levels due to reduced SI catabolism of circulating gastrin
87
treatment of short bowel syndrome
1. opiates to reduce stool output and establish effective diet (low fat, high carb) 2. consider and treat bacterial overgrowth if ileocecal valve is missing 3. PPI if acid hypersecretion is contributing 4. vitamin and mineral therapy 5. home PN if other methods fail 6. SI transplant
88
what are bacterial overgrowth syndromes
SIBO group of disorders with diarrhea, steatorrhea, and macrocytic anemia whose common feature is the proliferation of colonic type bacteria within the small intestine
89
what causes bacterial proliferation in SIBO
``` impaired peristalsis (functional stasis) changes in intestinal anatomy (anatomic stasis) direct communication between the small and large intestine ```
90
other names for SIBO
stagnant bowel syndrome | blind loop syndrome
91
bacteria commonly found in SIBO
e. coli | bacteroides
92
macrocytic anemia in SIBO
due to cobalamin, not folate def | bacteria need cobalamin for growth and use up the limited dietary amounts
93
steatorrhea in SIBO
impaired micelle formation reduced concentration of conjugated bile acids and the presence of unconjugated bile acids bacteroides can deconjugate bile acids and the unconjugated form is more rapidly absorbed
94
what if you don't have steatorrhea in SIBO, but there is still diarrhea present?
likely due to bacterial enterotoxins causing fluid secretion
95
examples of anatomic stasis
diverticula fistulas/strictures proximal duodenal afferent loop following subtotal gastrectomty and gastrojejunostomy bypass of SI (jejunoileal bypass or roux en y gastric bypass) dilation at site of previous intestinal anastomosis
96
examples of etiologies functional stasis
scleroderma | DM
97
etiologies of direct communication between small and large intestines
ileocolonic resection | enterocolic anastomosis
98
making a diagnosis of SIBO
1. low cobalamin and high folate 2. jejunal aspirate w increased levels of bacteria (culture and count) 3. breath hydrogen test w admin of lactulose 4. schilling test
99
10 signs of SIBO
``` gas bloating diarrhea ab pain/cramps constipation IBS or IBD food intolerances chronic illnesses B12 deficiency fat malabsorption ```
100
treatment of SIBO
1. surgical correction of anatomic blind loop if present | 2. broad spectrum antibiotics for 3 weeks for functional causes that cannot be corrected

GIR Test 4 (20 decks)

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