The colon Flashcards
which parts of the colon are
1) mobile
2) immobile
1) mobile
- ceacum (intraperitoneal) = quite mobile
- transverse colon = very mobile
- sigmoid colon = quite mobile
what are paracolic gutters
They are spaces between the colon and the abdominal wall. They are potential sites of pus collection
what are taeniae coli
3 distinct longitudinal bands of smooth muscle, running from caecum to distil end of sigmoid colon
where does the caecum and appendix normally lie
Both lie in the right iliac fossa
where does the sigmoid colon lie
lies in the left iliac fossa
what does the pancreas lie posterior to
stomach
what does the pancreas have
- head (with uncinate process)
- neck
- body
- tail
what type of a structure is the abdominal aorta
midline retroperitneal structure and anterior to the vertebral bodies
what are the 3 midline branches
- celiac truck = foregut organs
- superior mesenteric artery = midgut organs
- inferior mesenteric artery = hindgut
what are the branches of the superior mesenteric artery
- inferior pancreaticoduodenal
- middle colic
- right colic
- ileocolic
- appendicular
- jejunal and ileal
what are the branches of the inferior mesenteric artery
- left colic
- sigmoid colic
- superior rectal
what is the relevance of the arterial anastomoses between the superior mesenteric artery and the inferior mesenteric artery
Forms predominantly one artery called the marginal artery of Drummond. Collateral blood supply means structures towards the end of the colon can still get blood supply
what is haematemesis
vomiting blood
what are the 2 main venous systems of the body
- hepatic portal venous system - drains venous blood from absorptive parts of the GI tract and associated organs to the liver for cleaning
- systemic venous system - drains venous blood from all other organs and tissues into the superior or inferior vena cava
where does the inferior mesenteric vein drain blood
Drains blood from the hindgut structures to the splenic vein
where does the superior mesenteric vein drain blood
Drains blood from the midgut structures to hepatic portal vein
where does the splenic vein drain blood
Drains blood from foregut structures to hepatic portal vein
where does the hepatic portal vein drain blood
Drains blood from foregut, midgut and hindgut structures to the liver for first pass metabolism (cleaned)
where does the inferior vena cava (retroperitoneal) drain blood
Drains cleaned blood from the hepatic veins into the right atrium
what is the function of portal systemic anastomoses
at these sites the presence of small collateral veins means blood can flow both ways
where are the 3 portal systemic anastomoses
- distil end of oesophagus
- skin around umbilicus
- rectum/anal canal
what are clinical presentations of portal hypertension
- oesophageal varices
- “caput medusae”
- rectal varices
what are the 2 main types of idiopathic inflammatory bowel disease
Crohn’s disease and Ulcerative Colitis
what is Crohn’s disease
Chronic inflammatory and ulcerating condition of the GI tract that can affect anywhere from the mouth to the anus.
Most common in the terminal ileum and colon
what are the sites for Crohns
- 2/3 have small bowel involvement only
- 1/6 have colonic/anal disease only
- 1/6 have both
how does Crohns disease present
- abdominal pain
- small bowel obstruction
- diarrhoea
- bleeding PR
- anaemia
- weight loss
what is seen microscopically in Crohns disease
- chronic active colitis with granuloma formation
- increased chronic inflammatory cells in the lamia propria and crypt branching with granulomas
- large non-caseating granulomas
- patchy chronic active colitis
inflammation involves all layers of the wall
what denotes severe Crohn’s disease
deep fissuring produces “cobblestoning” of mucosa
summarise the pathology of Crohn’s disease
- segmental disease (patchy)
- Ileal and/or colonic chronic active mucosal inflammation including:
- Cryptitis
- Crypt abscesses
Transmural inflammation
Deep knife-like fissuring ulcers
Granulomas, 50%, Non- caseating
what are complications of Crohn’s disease
- Malabsorption
- Fistulas
- Anal disease
- Intractable disease
- Bowel obstruction
- Perforation
- Malignancy
- Amyloidosis
etc lots of complications
what genetic factors are associated with Crohn’s disease
- susceptibility locus on chromosome 16 … NOD2
- Association with HLA-DR1 and HLA-DQw5
what is the aberrant immune response of Crohn’s disease
Persistent activation of T-cells and macrophages (failure to switch off)
Excess proinflammatory cytokine production
Maybe alterable by changing intestinal microflora…”Probiotics”
what is the definition of Ulcerative Colitis
Chronic inflammatory disorder confined to colon and rectum
Mucosal and submucosal inflammation
Unknown aetiology
what sites is Ulcerative Colitis seen
Confined to the colon and rectum. Nearly always involves the rectum. Continuous and confluent extending proximally for varying lengths
what is the clinical presentation of Ulcerative colitis
- Diarrhoea
- Mucus
- Blood PR
Describe a pathological summary of Ulcerative Colitis
Continuous, diffuse disease
Rectal involvement, almost always
Superficial ulceration and inflammation
Chronic active colitis
- Cryptitis - Crypt abscess
No granulomas
what are the complications of Ulcerative Colitis
- Intractable disease
- Toxic megacolon
- Colorectal carcinoma
- Blood loss
- Electrolyte disturbance
- Anal fissures
What is the aberrant immune response
Persistent activation of T-cells and macrophages
Autoantibodies eg ANCA present
Excess proinflammatory cytokine production and bystander damage due to neutrophillic inflammation
Maybe alterable by changing intestinal microflora…”Probiotics”
what are comparisons of Crohns Disease and Ulcerative Colitis
Chronic diseases Unknown aetiology Ulceration Inflammation Relapsing and remitting course Bloody diarrhoea Both increase risk of cancer
what are differences between Crohns disease and Ulcerative Colitis
Ulcerative Colitis is diffuse, continuous disease Colon and rectum Rarely skips Mucosal ulceration and thin wall Superficial inflammation No granulomas Fistulae rare Cancer risk high Extra GI common
Crohns disease is patchy, segmental disease Anywhere in GI tract Skip lesions common Thickened bowel and stricture Transmural inflammation Granulomas present Fistulae common Cancer risk moderate Extra GI rare
what are the 3 zones in the liver used to describe patterns of liver injury
- periportal
- mid acinar
- pericentral
what can happen in the liver due to insult
- some liver insults can produce severe parenchymal necrosis but heal entirely by restitution
- some types of injury leave permanent damage
- some types of injury produce predictable pathological patterns
what is cirrhosis
severe scarring
what is the pathogenesis of liver disease
Insult to hepatocytes by viral, drug, toxin, antibody etc
leads to grading… degree of inflammation
leads to staging… degree of fibrosis
cirrhosis
what are consequences of acute liver failure
- complete recovery
- chronic liver disease
- death from liver failure
what are the 3 types of jaundice
- pre hepatic
- hepatic
- post hepatic
what is pre hepatic jaundice
Too much haem to break down
- haemolysis of all causes
- haemolytic anaemias
- unconjugated bilrubin
what is hepatic jaundice
Liver cells injured or dead
- Acute liver failure (viruses, drugs, alcohol)
- Alcoholic hepatitis
- Cirrhosis (decompensated)
- Bile duct loss (astresia, PBC,PSC)
- Pregnancy
what is post hepatic jaundice
Bile cannot escape into the bowel
- congenital biliary astresia
- gallstones block CBDuct
- strictures of CBDuct
- Tumours (Ca head of pancreas)
what is cirrhosis of the liver
Final common endpoint for liver disease
Irreversible
Defined by bands of fibrosis separating regenerative nodules of hepatocytes
Macronodular or micronodular (alcoholic)
Alteration of hepatic microvasculature
Loss of hepatic function
what are complications of cirrhosis
portal hypertension
ascites
liver failure
how is the toxic affect of alcohol brought about
The toxic effect of alcohol is mediated through altered fat metabolism and acetaldehyde production
what effect does continued heavy drinking have on the liver (weeks to months)
Leads to hepatocyte death and an inflammatory response including neutrophils
what effect does continued heavy drinking have on the liver (months to years)
eventually collagen is layed down, hepatocytes are ballooned, inflammation continues and remodelling of the intrahepatic blood flow occurs
what are some outcomes of alcoholic liver disease
- Cirrhosis
- Portal hypertension .. varices and ascites
- malnutrition
- hepatocellular carcinoma
- social disintergration
what is Non-alcoholic steatohepatitis (NASH)
Non-drinkers
Pathologically identical to alcoholic liver disease
Occurs in patients with diabetes, obesity, hyperlipidaemia
Now a severe problem overtaking alcohol in importance
Many patients of course have both
May lead to fibrosis and cirrhosis
what is hepetitis
inflammation of the liver
what are common causes of hepatitis
Hepatitis A,B,C,E
What is hepatitis A
- faecal oral spread
- short incubation period
- sporadic or endemic
- directly cytopathic
- no carrier state
- mild illness, usually full recovery
what is hepatitis B
- spread by blood, blood products, sexually
- long incubation period
- liver damage is by antiviral immune response
- carriers exist
- outcome is variable
what is hepatitis C
- spread by blood, blood products, possibly sexually
- short incubation period
- often asymptomatic
- disease waxes and wanes
- tends to become chronic
what is primary biliary cirrhosis
Rare autoimmune disease, unknown aetiology
Associated with autoantibodies to mitochondria
Females (90%)
Indication for biopsy: Stage the disease
May see granulomas and bile duct loss
Outcome: Unpredictable
Bile ducts are targets for inflammation
what is primary sclerosing cholangitis
Chronic inflammatory process affecting intra - and extra-hepatic bile ducts
Leads to periductal fibrosis, duct destruction, jaundice and fibrosis
Associated with Ulcerative Colitis
Males
Increased risk of malignancy in bile ducts and colon
what is cholangitis
inflammation of the bile ducts
what is haemochromatosis
Haemochromatosis is an inherited condition where iron levels in the body slowly build up over many years. Excess iron within the liver. Iron accumulates in hepatocytes
what is Wilsons disease
Inherited autosomal recessive disorder of copper metabolism
Copper accumulates in liver and brain (basal ganglia)
Kayser-Fleischer rings at corneal limbus
Low serum caeruloplasmin
Causes chronic hepatitis and neurological deterioration
what is alpha-1-antitrypsin deficiency
Inherited autosomal recessive disorder of production of an enzyme inhibitor
Causes empysema and cirrhosis
Cytoplasmic globules of unsecreted globules of protein in liver cells
what are examples of primary tumours of the liver (rare)
- Hepatocellular adenoma
- Hepatocellular carcinoma (Hepatoma)
what are examples of secondary tumours in the liver (common)
- Multiple
- Metastases from colon, pancreas, stomach, breast, lung, others….
