Pathology- the small bowl Flashcards
What is the small bowl
the small intestine
what is the innermost cell of the small bowl
enterocytes lined with villi
what is the main function of the villi
absroption
what is the blood supply to the small bowl
entire supply from superior mesenteric
what can cause ischaemia of the small bowl
mesenteric artery occlusion
non occlusive perfusion insufficiency
what can cause mesenteric artery occlusion
mesenteric artery atherosclerosis
thromboembolism from heart (e.g. A fib)
what can cause a non occlusive perfusion insufficiency
shock (when haemorrhaging as brain, heart and lungs a priority)
strangulation obstructing venous return (e.g. hernia or adhesion)
drugs (e.g. cocaine, causes spasm of intestinal wall)
hyperviscosity
what pain is associated with ischaemia of the small bowl
acute pain as usually acute, can by chronic
why is the mucosa the area most affected by an infarction (the effects of hypoxia)
as it is the most metabolically active area
what increases with the period of hypoxia
the greater the dept of the damage to the bowl wall and likelyhood of complications
in non occlusive ischaemia when does much of the tissue damage occur
after reperfusion
what is a possible outcome from the following
- mucosa infarct
- mural infarct
- transmural infarct
different types of infarct occur as the length og time of ischaemia increases. the outcomes also get worse
- regeneration
- stricture (abnormal narrowing caused by firbous scarring during healing)
- gangrene (when infarct goes through the bowl)
what are the complications of ischaemia of the small bowl
mucosa
resolution
mural
fibrosis, stricture, chronic ischaemia, mesenteric angina, obstruction,
transmural
gangrene, perforation, peritonitis, sepsis, death
what is meckel’s diverticulum
is a result of imcomplete regression of vitello-intestinal duct (embryological feature)
describe meckels diverticulum
Tubular structure, 2 inches long, 2 foot above IC (illeocecal) valve in 2% of people
May contain heterotopic gastric mucosa
what can a mekels diverticulum cause
bleeding, perforation or diverticulitis which mimicks appendicitis, peptic ulcers
Commonly assymptomatic, incidental finding
what tumours are most common in the small bowel
primary tumours rare secondary tumours (metastases from ovary, colon and stomach) more common primary tumours include -lymphomas -carcinoid tumours -carcinomas (in order of commonness)
what type are the lymphomas of the bowel
non hodkins in type
how are lymphomas of the bowel treated
surgery and chemotherapy
where is the most common site for a carcinoid tumour in the small bowl
the appendix
describe carcinoid tumours of the bowel
small, yellow, small growing, locally invasive, produces hormone like substances, if metastases to liver causes a carcinoid tumour producing flushing, diarrhoea and head aches
what cancer is associated with coeliac disease
lymphomas
describe carcinomas of the small bowel
rare, presents late, metastases to lymph nodes and liver occur
what bowl cancer is associated to crohns and coeliac disease
carcinoma (as they are predisposed to rarer cancers)
what are the symptoms of an appendicitis
vomiting, abdominal pain, right illiac fossa, increased white cell count
what can cause an cute appendicitis
unknown (most common), faecoliths (dehydration), lymphoid hyperplasia, parasites, tumours (rare)
describe the pathology of an acute appendicitis
Acute inflammation (neutrophils)- must involve a muscle coat
Mucosal ulceration
Serosal congestion, exudate
Pus in lumen
what happens to the wall of the appendix during an acute appendicitis
is thickened, neutrophils invade it, inflammation
what are the complications of an appendicitis
peritonitis, rupture, abscess, fistula, sepsis and liver abscess
how can an acute appendicitis cause a liver abscess
can spread to liver via portal system causing abscess of liver
what is coeliac disease caused by
an abnormal reaction to a constituent of wheat flour, gluten, which damages enterocytes and reduces absorptive capacity- damages villi
when can coeliac disease present
any time
what is coeliac disease strongly associated with
HLA-B8, dermatitis herpeformis, childhood diabetes
what is the suspected auto antigen (toxic agent) in coeliac disease
gliadin (component of gluten)
-tissue injury may be a bystander effect of abnormal immune reaction to Gliadin
what is T cells role in coeliac disease
Mediated by T-cell lymphocytes which exist within the small intestinal epithelium ‘intraepithelial lymphocytes’ (IELS)
what is the normal lifespan of an enterocyte
72 hours
how is coeliac disease seen in the gut
increasing loss of enterocytes due to IEL mediated damage
This leads to loss of villous structure, loss of surface area,
a reduction in absorbtion and a flat duodenal mucosa
(e.g. flat mucosal biopsy with total villous atropy)
what is the morphology of coeliac disease
increased inflammation in lamina propria, increased intraepithelial lmphocytes
what part of the bowl is usually worse in coeliac disease
proximal
what antibodies will be found in someone with coeliac disease
anti-TTG, anti-endomesial, anti glandin
what are the metabolic effects of coeliac disease
Malabsorbtion of sugars, fats, amino acids, water and electrolytes
Malabsorbtion of fats leads to steatorrhea (excessive fat in poo)
Reduced intestinal hormone production leads to reduced pancreatic secretion and bile flow (CCK) leading to gallstones
what are the clinical effects of malabsorption
weight loss, anaemia, abdominal bloating, failure to thrive, vitamin deficiencies
what are 4 rare complications of coeliac disease
T-cell lymphomas of GI tract
Increased risk of small bowel carcinoma
Gall stones
Ulcerative-jejenoilleitis
