L6 Malabsorption and Small Intestine Neoplasms Flashcards
(32 cards)
Specific vs. Generalized Malabsorption?
*Generalized malabsorption–absorption of several or all major nutrient classes is impaired
*Specific malabsorption–identifiable molecular defect that causes malabsorption of a single nutrient
Malabsorption results from a disturbance in at least one of the four phases of nutrient absorption. What are these 4 stages?
- intraluminal digestion (emulsification helps)
- terminal digestion (brush border)
- transepithelial transport
- lymphatic transport of absorbed lipids.
Causes of Malabsorption (7)
- Defective Intraluminial Digestion
- Primary Mucosal Cell Abnormalities
- Defective Epithelial Transport
- Reduced Small INtestinal Surface Area
- Lymphatic Obstruction
- Infection
- Latrogenic
Example of Malabsorption caused by Disaccharide Deficiency?
Lactose Intolerance
Congenital -Rare
Acquired-Common post viral/bacterial infection
Bacterial fermentation of the unabsorbed sugars => increased hydrogen production =>measured in exhaled air by gas chromatography
Example of malabsorption caused by Defective Epithelial Transport?
Abetalipoproteinemia
Pathogenesis of Abetalipoproteinemia?
Faulty microsomal triglyceride transfer protein (MTP) gene
=> Impaired transepithelial transport of lipids from enterocytes to blood
Symptoms of Abetalipoproteinemia?
Steatorrhoea (Fatty Stools)
Diarrhoea
Lipid vacuoles visible in enterocytes
Failure to thrive
Malabsoprtion conditions caused by Reduced Small Intestinal Surface Area?
Crohn’s Disease
Mucosal inflammation
Scarring
Fistulas
Common post-surgery Granulomas -TB
Coeliacs Disease
abnormal immune reaction to gluten
=> damage to the surface enterocytes of the small intestine
=> severely reduces their absorptive capacity
Presentationn of Coeliac’s DIsease?
Diarrhoea/Steatorrhoea
Flatulence
Weight loss
Fatigue
EASY TO MISS: Majority of pts. Expressed mild, non-specific symptoms of Bloating/indigestion
Aymptomatic w/ unexplained iron deficiency anemia
Tissue injury in Coeliac’s Disease is primarily a result of ____________
Tissue injury primarily result of immune response
◊ Perturbed T-Cell function
◊ Genes cause amplified immune response (IL-2, 21)
Due to high _________content many gluten peptides are resistant to intestinal peptidases
Due to high proline content many gluten peptides are resistant to intestinal peptidases
__________ => post epidemic coeliac surge
Intestinal viral infections => post epidemic coeliac surge
Roles of Gliadin/Glutenin in Coeliac Disease
Gliadin/Glutenin: Direct effects on intestinal permeability through the disruption of tight junctions between enterocytes => gluten exposure to immune system
Gliadin: glutamine allows it to react w/ tissue transglutaminase => Potent T-CELL Activator
What occurs to Jejunal Mucosa in Coeliac’s Disease?
Total Villous Atrophy
Where is Coeliac’s Disease most severe?
proximal small intestine: duodenum and proximal jejunum
Clinical Associations of Coeliac’s Disease?
Skin blistering ‘dermatitis herpetiformis’: IgA against epidermal transglutaminase similar to tissue transglutaminase
Splenic atrophy
Atopy and Autoimmune disease
Complications of Coeliac’s Disease?
Ulceration of small intestine from chronic ulcerative enteritis
Increased risk of GI Adenocarcinomas + Intestinal Lymphoma
Esophageal squamous cell carcinoma (50-100x)
Osteoporosis, Muscle wasting, dental enamel hypoplasia
Diagnosis of Coeliac’s Diseease
Detection of circulating tissue transglutaminase or anti-endomysial antibodies strongly favors the diagnosis
Definitive diagnosis rests upon:
◊ Clinical documentation of malabsorption
◊ Histological confirmation on small bowel biopsy
◊Symptomatic and mucosal histology improvement upon gluten withdrawal from diet
Causes of Lymphatic Obstruction leading to Malabsoprtion?
Lymphoma
TB
Parasitic Infection leading to Malabsorption
Giardiasis
Trophozoites
pear shaped w/ 2 nuclei
Cause of traveler’s Diarrhea (Contaminated water)
Tropical Sprue Characteristics/Treatment
Characterized by:
chronic diarrhea, weight loss, lethargy, malaise
macrocytic anemia due to folate or vitamin B12 deficiency
Looks like coeliac disease but DOESN’T respond to gluten restriction
Treatment:
May be relieved by tetracyclines
Whipple Disease Characteristics/Treatment
Rare bacterial infection
Lymphadenopathy, CNS + Joint Symptoms
Infiltration of lamina propria with FOAMY MACROPHAGES with abundant PAS(d)+
Treatment:
prolonged cephalosporin and co-trimoxazooe
Latrogenic Causes of Malabsorption
i. Subtotal gastrectomy (B12)
ii. Short gut syndrome, following extensive surgical resection
iii. Distal ileal resection or bypass
iv. Radiation enteropathy
Excessive fecal fat and bulky, frothy, greasy, yellow or clay-colored stools
Significance?
Steatorrhea: excessive fecal fat and bulky, frothy, greasy, yellow or clay-colored stools
hallmark of malabsorption
