2- pathology of small bowel Flashcards
where is small bowel?
runs from gastric pylorus to ileocaecal valve
small bowel = small intestine
is duodenum, jejunum and ileum intraperitoneal or retroperitoneal?
- duodenum is retroperitoneal (apart from 1st part which is intraperitoneal)
- jejunum + ileum is intraperitoneal
is walls of jejunum or ileum thicker?
wall of jejunum are thicker due prominent mucosal folds (plicae circulares)
what is purpose of villi in mucosa of small intestine?
location for digestion and absorption of nutrients from food (into columnar cells)
what is function of crypts in small intestine?
secrete ions, water, immunoglobulins and antimicrobial peptides into the lumen
where is absorption of vitamin b12?
terminal ileum (it’s joined by intrinsic factor in stomach)
where is iron/folate absorbed?
duodenal and proximal jejunum
what is coeliac disease?
=abnormal immune response to gluten leading to inflammation & damage of small intestine
- immune mediated disorder
- triggered by ingestion of gluten
- associated with other autoimmune disease like type 1 diabetes, thyroiditis, sjogren syndrome, IgA nephropathy
what are clinical presentations of coeliac disease?
all pretty non specific - diarrhoea, bloating, fatigue, anemia, vitamin malabsorption
what are clinical presentations of coeliac disease in children?
irritability, failure to thrive, weight loss, abdominal distension, diarrhoea, anorexia
what is dermatitis herpetiformis?
itchy, blistering skin lesions in 10% of patients with coeliac
= caused by the deposit of immunoglobulin A (IgA) in the skin
what can be measured in coeliac disease to help diagnose?
- IgA antibodies like specifically tissue transglutaminase (tTG) & endomysial
- gliadin
what is major risk of coeliac disease if it’s not well maintained?
Increased risk of malignancy – specifically enteropathy associated T cell lymphoma
what is gliadin?
= component of gluten - it’s the suspected toxic agent which triggers abnormal immune reaction (antibodies formed and cause activation of T cells that go to duodenum and damage epithelium and enterocytes, destroying + reducing absorptive capacity)
what is histologically different of coeliac disease?
the villi aren’t big nice projections - sort of flattened
what are characteristic features histologically of coeliac disease?
- loss in villous height (flat), intraepithelial lymphocytes (top cell layer has a lot of dark cells within it)
- at base of crypts big hyperplastic cells trying to regenerate damage
*lymphocytes infiltrate in epithelium
what is management of coeliac disease?
gluten free diet →resolution of symptoms, reduction in antibody titre →restores normal small bowel microscopic appearance within 6-24 months
what are different ways mesenteric vessels can be blocked causing small bowel ischaemia?
- Thrombosis due to atherosclerosis obstructing blood flow causing ischaemia
- vasculitis = inflammation of blood vessels, triggered by autoimmune diseases, neoplasia, cirrhosis, trauma, compression of portal drainage
- Emboli = origin from atheromas in aorta/cardiac mural thrombi
what can cause intestinal hypoperfusion which can lead to small bowel ischaemia?
Intestinal hypoperfusion can also occur due to cardiac failure, shock, dehydration or vasoconstrictive drugs e.g. adrenaline
what is macroscopic appearance of ischaemia of small bowel?
dusky serosa (external surface of unopened intestine) & dark coloured mucosa due to haemorrhage (internal intestinal surface)
what is summary of what happens in ischaemic small intestine?
attenuation of villous epithelium →atrophy →fibrosis of lamina propria →ulceration →haemorrhage →necrosis →eventually involves all layers
*once muscularis propria gone = bowel no longer viable
what is complication of ischaemia of small bowel - if not removed in time?
fibrosis →stricture →obstruction (fills with gas) →chronic ischaemia “mesenteric angina” →gangrene, gets thin →perforation which gets peritonitis →sepsis which can lead to death
what are primary tumours of small bowel? and how common?
they’re rare and examples = lymphomas, neuroendocrine neoplasms (carcinoid) , carcinoma
what are lymphomas of small bowel?
All are non-Hodgkins type
* MALTomas (mucosal associated lymphoid tissue): B cell derived
* Enteropathy associated T cell lymphoma: associated with coeliac
