Pathophysiology of Small Intestine Flashcards Preview

DEMS: Unit 1 > Pathophysiology of Small Intestine > Flashcards

Flashcards in Pathophysiology of Small Intestine Deck (17):
1

Mechanism/cause of diarrhea (general)

  • occurs when colonic water load exceeds absorptive capacity
  • A) small intestinal output substatantially increases
  • B) colonic absorptive ability decreases/overwhelmed

2

Major types of diarrhea

  • watery stool
    • osmotic
    • secretory
  • steatorrhea (fecal fat +)
    • malabsorption
    • maldigestion
  • inflammatory/exudative (often bloody)
    • crohn's
    • ischemia
    • invasive infection
  • function (Irritable Bowel Syndrome)

3

Definition/type of watery stool

  • Watery = Stool osm gap= 290- 2(stool Na + stool K
  • Osmotic (gap >50mOsm due to unmeasured Osm)
  • Secretory (gap<50mOsm)

4

Major causes of steatorrhea

  • Malabsorption
    • i.Celiac
    • ii.Whipple’s disease
    • iii.Small bowel bacterial overgrowth
    • iv.Short gut (small bowel) from surgery
  • Maldigestion
    • i.Pancreatic insufficiency
    • ii.Biliary obstruction

5

Major causes of inflammatory/exudative diarrhea

  • Crohn’s disease
  • Ischemia
  • Invasive infections (colon)
    • i.C. difficile
    • ii.EHEC
    • iii.Amebiasis
    • iv.Shigella

6

Characteristics of Functional Diarrhea

  • Functional = Irritable Bowel Syndrome
  • Usually watery diarrhea
  • Diagnosis of exclusion

 

7

Major causes of fat malabsorption

  • pancreatic insufficiency ==> impaired lipolysis
    • chronic pancreatitis <==alcoholism
  • liver disease ==> decreased bile ==> decreased fat absorption
    • alcoholic cirrhosis
    • primary biliary cirrhosis
    • biliary obstruction
  • gastric disorders
    • impaired mixing
    • early arrivial of ingested food to small bowel before pancreatic enzymes/bile
  • small intestinal bacterial overgrowth (SIBO)

8

Caues/mechanism of small intestinal bacterial overgrowth (SIBO)

  • major causes =
    • hypomotility (DM, scleroderma)
    • partial obstruction
    • diverticula
    • decreased gastric acid secretion
  • bacteria in intestinal lumen ==>
    • inactivated bile acids
    • reduced enterokinase effectiveness
    • disrupts small bowel motility

9

Clinical presentation of SIBO

  • diarrhea
  • steatorrhea
  • abdominal pain
  • flatulence
  • bloating
  • weight loss
  • later:
    • fat-soluble vitamin deficiencies (A,D, E)
    • B12 deficiency
    • serum folate = normal to high

10

Structural diseases that lead to malabsorption

  • mechanism: damage ==> decreased absorptive surface area
  1. Intestinal inflammation and villus flattening (celiac sprue, infection, tropical sprue, graft vs host disease, Whipple’s disease)
  2. Ulceration NSAIDs
  3. Crohn’s Disease 
  4. Ischemia 
  5. Infiltration (amyloidosis, lymphoma)
  6. Other (byapass, extensive small intestine resection)

11

Pathophysiology of Celiac disease

  • "celiac sprue" = "gluten-sensitive enteropathy" or "celiac disease"
  • inflammatory disease of small intestine due to immune response to peptides of gluten
  • presents @ weaning or in adults
  • loss of villi due to increased intraepithelial lympthocytes AND
  • crypt hyperplasia ==> malabsorption

12

Clinical presentation of celiac disease

  • sx of malabsorption
    • steatorrhea
    • diarrhea
    • weight loss
    • bloating
    • abdominal pain
  • carb/fat/protein malabsorption occur due to villus destruction
  • celiac occurs @ proximal small intestine ==> iron and folate malabsorption

13

Dx of celiac disease

  • intestinal biopsy:
    • villous flattening
    • intraepithelial lymphs
    • crypt hyperplasia
  • serologic tests
    • anti-endomysial antibodies
    • anti-tissue transglutaminases (tTg) IgA antibodies
    • anti-gliadin IgA and IgG

14

Tx of SIBO

  • antibiotics
    • e.g. cirprofloxacin

15

Major types of appendix tumors

  • carcinoid
    • neuroendocrine
    • metastases ==> liver ==> serotonin syndrome
      • episodic flushing, diarrhea, wheezing and R-side valvular heart disease
  • epithelial tumors
    • adenocarcinoma

  • secondary tumors (metastases)

16

Definition/major causes of osmotic diarrhea

Osmotic (gap >50mOsm due to unmeasured Osm)

i.Lactose intolerance
ii.Sorbitol
iii.Fructose
iv.Magnesium containing laxatives

17

Definition/major causes of secretory diarrhea

Secretory (gap<50mOsm)

i.Bacterial toxins (V. cholera etc)
ii.Neuroendocrine tumors (Gastrinoma, VIPoma, Carcinoid)
iii.Bile salt (e.g terminal ileal resection)
iv.Stimulant laxatives
v.Motility disorders (Diabetes, IBS)