Malabsorption and Small Intestinal Neoplasms Flashcards
What are the causes of malabsorption? (7)
- defective intraluminal digestion
- primary mucosal cell abnormalities
- defective epithelial transport
- reduced small intestinal surface area
- lymphatic obstruction
- infection
- iatrogenic
What are examples of defective intraluminal digestion? (3)
- pancreatic insufficiency
- zollinger ellison syndrome
- inadequate emulsification of fat
What are examples of primary mucosal cell abnormalities? (1)
lactose intolerance
What is an example of defective epithelial transport? (2)
- abetalipoproteinaemia
2. primary bile acid malabsorption
What is an example of reduced small intestinal surface area? (2)
- gluten sensitive enteropathy
2. Crohn’s disease
What is an example Lymphatic obstruction? (2)
- lymphoma
2. TB
What are examples of infectious causes of malabsorption? (4)
- acute infectious enteritis
- parasitic infestation
- tropical sprue
- whipple disease
What are iatrogenic causes of malabsorption? (4)
- subtotal gastrectomy
- short gut syndrome
- distal ileal resection or bypass
- radiation enteropathy
What is the common presentation of malabsorption?
chronic diarrhoea
What are examples of malnutrition (not malabsorption)? (2)
- marasmus
2. Kwashiorkor
What are the most common malabsorption syndromes in the Western world? (3)
- coeliac disease
- pancreatic insufficiency
- Crohn’s disease
What causes coeliac disease?
- abnormal immune reaction to gluten which results in damage to the surface enterocytes of the small intestine and severely reduces their absorptive capacity
How does coeliac disease present in severe cases? (4)
- diarrhoea/steatorrhoea
- flatulence
- weight loss
- fatigue
What is the pathogenesis of coeliac disease? (6)
- Complex
- multifactorial
- incompletely understood
- environmental trigger
- genetically susceptible
- +/- immune dysregulation
What happens when gluten is consumed in coeliac disease? (7)
- consumption of gluten
- tissue transglutaminase released
- modification of gliadin from gluten proteins
- pathogenic T cells react to and are activated by modified gliadin
- mediate chronic intestinal inflammation
- epithelial damage resulting in villous atrophy, crypt hyperplasia and loss of brush border
- impaired resorption of nutrients in the small intestine
What is the genetic predisposition associated with coeliac disease? (2)
- HLA-DQ2
2. HLA-DQ8
What are the consequences of villous atrophy? (2)
- total malabsorption
2. lactose intolerance due to disaccharidase deficiency
Where is coeliac disease more severe? (2)
- duodenum
2. proximal jejunum
how can coeliac disease be diagnosed using tests?
detection of circulating tissue transglutaminase or anti-endomysial antibodies
How is coeliac disease definitively diagnosed? (3)
- clinical documentation of malabsorption
- histological confirmation on small bowel biopsy
- improvement in both symptoms and mucosal histology on gluten withdrawal from the diet
What are the clinical associations of coeliac disease? (2)
- dermatitis herpetiformis
2. splenic atrophy
What is the pathogenesis of dermatitis herpetiformis?
IgA against epidermal transglutaminase
What are the complications of coeliac disease? (3)
- chronic ulcerative enteritis
- GI adenocarcinomas
- enteropathy associated T cell lymphoma
What is tropical sprue?
pathological changed identical to those found in coeliac disease but less severe and more distal
What are the features of tropical sprue? (5)
- chronic diarrhoea
- weight loss
- lethargy
- malaise
- macrocytic anaemia
What is used to treat tropical sprue?
tetracyclines
What causes giardiasis?
infection with giardia duodenalis
What causes whipple disease?
tropheryma whippelii
How does whipple disease present? (4)
- malabsorption
- lymphadenopathy
- arthralgia
- CNS involvement
What is seen histologically in whipple disease?
infiltration of the lamina propria by numerous foamy macrophages
How is whipple disease treated? (2)
- cephalosporin
2. co-trimoxazole
What are the two types of lactase deficiency?
- congenital autosomal recessive
2. acquired
How does lactase deficiency present? (3)
- fullness
- flatulence
- osmotic diarrhoea from unabsorbed lactose
What is the cause of abetalipoproteinaemia?
faulty microsomal triglyceride transfer protein (MTP) gene (autosomal recessive)
What is the pathogenesis of abetalipoproteinaemia?
impaired transepithelial transport of lipids from enterocytes to blood
What is seen histologically in abetalipoproteinaemia?
lipid vacuoles visible in enterocytes
What are the symptoms of abetalioproteinaemia? (3)
- steatorrhoea
- diarrhoea
- failure to thrive
What is the presentation of small intestinal adenocarcinoma? (5)
- early obstructive jaundice
- obstruction
- nausea
- vomiting
- occult blood loss
Where does small intestinal adenocarcinoma occur usually?
duodenum
What is the major risk factor for small intestinal adenocarcinoma?
chronic inflammation associated with crohn’s disease
What are the associations of small intestinal adenocarcinoma? (4)
- crohn’s disease
- familial adenomatous polyposis coli
- HNPCC
- Peutz Jegher’s syndrome
What is the most common site for carcinoid tumours of the intestine?
appendix
What cells are carcinoid tumours of the intestine derived from?
resident endocrine cells
What occurs in carcinoid syndrome?
tumour secretion of serotonin
When is carcinoid syndrome seen?
hepatic metastases
How is carcinoid syndrome diagnosed?
excess 5HIAA in the urine
What is associated with gastrointestinal lymphoma? (4)
- chronic gastritis
- chronic sprue like conditions
- mediterranean regions
- immunodeficiency
What is immunoproliferative small intestinal disease associated with?
campylobacter jejuni
How does immunoproliferative small intestinal disease present in young adults?
- malabsorption
- anorexia
- fever
