Small Intestine Disorders Flashcards
Appendix function
perhaps vestigal remnant, storage for good bacteria, maybe immune regulator
Diseases of Appendix
appendicitis most common, tumors rare
Appendix tumors
Rare
- Carcinoid (0.5% of appendectomy specimens) (neuroendocrine)
- metastasis rare if tumor
absorption/transport of fluids
9L secreted/ingested, 8.9 L absorbed (SI–8.4 L and colon about 400 mL), 100 ml secreted
Malabsorption/maldigestion
syndrome of disordered/inadequate nutrient absorption
Malabsorption clinical signs
weight loss, diarrhea, steatorrhea, vitamin deficiencies
- pale, bulky, malodorous stool (float/difficult to flush, oily residue)
Causes of malabsorption
Surgery, bacterial overgrowth, meds, pancreatic insufficiency, liver dz, intestinal inflammation/villus flattening, ulceration, ischemia, infiltration
surgical causes of malabsorption
gastric bypass, small bowel resection
medications causing malabsorption
cholestyramine - ADEK, phenytoin-folate
intestinal inflammation/villus flattening causes
celiac sprue, Whipple’s disease, tropical sprue
Infiltration causing malabsorption example
amyloidosis
Pancreatic insufficiency
90% of pancreas burned out
- Digestive enzymes (lipase, trypsin, etc)
lipid maldigestion first, protein malabsorption, carb malabsorption rare
chronic pancreatitis
cystic fibrosis
Liver dz
Cirrhosis
- decreased fxn of hepatocytes, decreased bile formation (need for lipid absorption)
Biliary obstruction
Gastric bypassp roblems
inadequate mixing of food with biliary and pancreatic secretions
gastric bypass vitamin deficiencies
- B12, Fe, Ca, Vit D most common
- Vit C, Cu rare
- Prevent: multivitamin
bacteria in ailimentary tract
400-500 species
Small Bowel bacterial overgrowth
- Normal bacteria
clinical signs of bacterial overgrowth in SI
diarrhea, steatorrhea, abd pain, bloating, weight loss
Hypomobility problems causing bacterial overgrowth
diabetes, scleroderma, narcotics
anatomic abnormalities causing SI bacterial overgrowth
diverticular, blind loop (BII), IC valve resection
Bacterial overgrowth vitamin deficiencies
fat soluble vitamin/B12 deficiency
- bacteria de-conjugate bile salts and consume B12
Bacterial overgrowth folate levels
normal to high–>bacterial production
Bacterial overgrowth diagnosis
aspiration of duodenum with culture, glucose-hydrogen breath test, empiric treatment with antibiotics
Treat bacterial overgrowth
antibiotics (Ciprofloxacin, i.e.)
Fat Malabsorption Vit
lll
Celiac Sprue
gluten sensitive enteropathy (wheat, barley, rye)
- inflammatory dz of SI –> loss of villi, crypt hyperplasia, IE Lymphocytes
Prevalence of celiac sprue
- 5-1% of US population–80% asymptomatic
- incidence increases with age
Typical signs/symptoms of celiac sprue
abd pain/distention, anorexia, steatorrhea, diarrhea, flatulence, failure to thrive, vomiting
Atypical Celiac Sprue signs/symptoms
Fe deficiency anemia, Dermatitis herpetiformis, Liver function tests (AST, ALT elevations), cerebellar ataxia, osteoporosis, oral apthous ulcers
Celiac pathogenesis
- associated with autoimmune dz (Female: male 2:1)
- APC-MHC II present gluten peptides
- CD4 T cell response
- all have Ab to tissue transglutaminase
Alleles associated with Celiac
HLA-DQ2, HLA-DQ8 (40% ofUS)
- 2-5% gene carriers develop dz
Celiac diabnosis
- findings on biopsy
- Serology tests: anti-tissue transglutaminases (BEST), anti endomysial antibodies, anti=gliadin IgA and IgG
Celiac treatment
Gluten free diet
- corn, rice, soy, millet
- expensive but prices have gone down
Tropical Sprue population/cause
- tropics residents/visitors (around 30 days)
- Cause: bacterial toxins or colonization of aerobic coliform bacteria
Classic presentation of tropical sprue
Megaloblastic anemia from B12 and folate deficiency
Diagnosis of tropical sprue
intestinal biopsy with villous flattening/travel hx
Treatment of tropical sprue
Antibiotics, B12, folate
Whipple’s dz cause
RARE!!
- Gram + actinomycete: T whippelii
signs of Whipple’s d
fever, joint, pain, diarrhea, abd pain, CNS-neurologic symptoms
Diagnosis of Whipple’s dz
PAS+ Macrophages on biopsy, PCR
Treatment of Whipple’s dz
1 yr antibiotics
Mesenteric Ischemia
- atherosclerosis, clot, radiation
Causes/sxs of acute mesenteric ischemia
- Acute: embolus –> severe abd pain
- usually some necrotic bowel and need surgery
Causes/symptoms of chronic mesenteric ischemia
- Chronic: 2 of 3 major vessels occluded
- Sxs- post-prandial abd pain, weight loss, sitophobia, malabsorption
Malabsorption diagnostic tests
- focused testing- clinic scenario
- fecal fat, vitamin levels, CBC, albumin, CT-SI/liver/pancreas/bile ducts, endoscopy
SI tumor prevalence
very rare cause of primary tumors (
Type of SI tumors/prevalence
Adenocarcinoma (47%–most duodenum)> Carcinoid (28%)> sarcoma (13%)> Lymphoma (12%)
- metastasis
presentation of SI tumor
sxs of obstruction (abd pain/distention, decreased tool output)
2 main causes of diarrhea
Decrased absorption of fluid/electrolytes, increased secretion of fluid/electrolytes
Diarrhea main concept
colonic water load > absorptive capacity
Causes of decreased fluid/electrolyte absorption
- inhibited/defective absorption of fluid and/or electrolytes
- luminal osmotic agents
- increased motility with decreased contact time
Causes of increased fluid/electrolyte secretion
stimulated anion secretion, increased crypt secretion
4 classes of stool
Fatty, watery, inflammatory/exudative, functional
Fatty diarrhea
malabsorption/maldigestion
watery diarrhea causes
osmotic/secretory
Causes of Osmotic watery diarrhea
- *poorly absorpbed luminal osmols
- Carbohydrate malabsorption (lactose, sorbitol, fructose)
- Osmotic laxatives (Mg containing, phosphagte, sulfate (colonoscopy bowel preps)
Osmotic vs secretory diarrhea
- measure stool Na/K
- nl osmolarity = 290 mOsm
- Osm gap = 290-2 (stool Na + K)
- if difference >50 mOsm, diarrhea is osmotic
- difference
Lactose Intolerance
> 50% world down-regulates lactase after weaning
- lactose indigestion –> osmotic diarrhea , flatulence (colonic bacteria)
lactose intolerance cause
mutations in lactase promoter –> lactase persistence in 80% Northern European and nomadic popoulations
Secretory Watery Diarrhea causes
- Bacterial toxins
- Neuroendocrine tumors
- Ileal bile salt malabsorption
- stimulant laxatives
- Disordered motility/regulation (diabetic neuropathy, postvagotomy, IBS)
Fatty Diarrhea causes
- malabsorption syndormes
- maldigestion /malabsorption
malabsorption syndromes
- mucosal dzs (Celiac dz, Whipple’s)
- short bowel syndrome
- small bowel bacterial overgrowth
maldigestion/malabsorption syndromes
- pancreatic insufficiency
- inadequate luminal bile salt concentration (chronic lever dz, biliary obstruction)
Inflammatory diarrhea causes
Infection, IBD( Crohn’s, UC), ischemia
mechanisms of inflammaory diarrhea
1) stimulated secretion and inhibited absorption
2) stimulation of enteric nerves causing propulsive contractions and stimulated secretion
3) mucosal destruction and increased permeability
4) nutrient maldigestion/malabsorption
Fecal leukocytes in intestinal infections
- Present - Shigella, Campylobacter, Enterohemorrhagic/enteroinvasis E. coli
- Variable (Salmonella, Yersinia, C diff–pseudomembranous colitis)
- Absent (V. cholerae, Enterotoxigenic E coli, Giardia lamblia)
Inflammatory Diarrhea Diagnosis
- Infection – stool culture, Endoscopy
- Ischemia (CT scan, Endoscopy-colon)
- IBD - endoscopy
Irritable Bowel Syndrome (IBS)
Abd pain and altered bowel habits in absence of organic cause
- pain improved with defecation
- pain onset with change in stool frequency or appearance
- constipation and/or diarrhea
IBS prevalence
10-15% population
IBS possible mechanisms
visceral hypersensitivity, carbohydrate malabsorption, low-grade inflammation
When to be concerned with IBS (maybe other problem)
weight loss, rectal bleeding, anemia, nocturnal symptoms, electrolyte abnormalities, elevated inflammatory markers
Bacterial toxins asociated with secretory watery diarrhea
V cholerae, E. coli enterotixins
Neuroendocrine tumors associated with secretory watery diarrhea
gastrinoma, VIPoma, carcinoids, calcitonin
