1 Flashcards
Why does cholecystitis cause shoulder pain?
This is referred pain.
the phrenic nerve gives sensory fibres to the adjacent diaphragm, and potentially the gallbladder. Many of the fibres in the phrenic nerve come from the C4 spinal nerve, which is also sensory to the shoulder
Explain the hormonal control of gallbladder contraction
cholecystokinin is released in response to the entry of fatty acidic chyme into the duodenum. CCK stimulates gall bladder contraction and relaxation of the sphincter of oddi
Blood results:
1) +++ elevated ALP
2) elevated ALT
3) ++ Bilirubin
4) ++ conjugated bilirubin
Explain the diagnosis and reasoning behind it.
This is a case of post-hepatic obstructive jaundice.
Bilirubin is mainly conjugated in the liver. The high levels of conjugated bilirubin indicate that it must have passed through the liver.
ALP is produced by the epithelial lining of the bile ducts. Elevated ALP therefore suggests obstruction of these ducts.
Jaundice
reflects elevated serum bilirubin levels.
usually clinically evident when greater than twice the normal level
Which cell organelle is responsible for the conjugation of bilirubin?
the endoplasmic reticulum
Into which lumen is conjugated bilirubin directly secreted by hepatocytes?
bile canaliculus
Which vein carries resorbed urobilinogen from the terminal ileum to the portal vein?
superior mesenteric vein
What does ERCP stand for
endoscopic retrograde cholangiopancreatography
functions of cholesterol
steroid hormone precursor
component of cell membranes
precursor of bile acids
component of plasma lipoproteins
explain how statins work
statins competitively inhibit the action of HMG-CoA reductase, decreasing hepatic cholesterol synthesis
They also induce LDL receptor expression, and therefore enhance cholesterol clearance by the liver
Name four organisms that commonly cause bloody diarrhoea
1) campylobacter
2) salmonella
3) E. coli
4) Shigella
Also entamoeba histolytica
Where is CRP produced?
Hepatocytes
What is the clinical significance of elevated CRP?
Nonspecific indicator of inflammation or infection in the body
CRP is an acute phase reactant protein
What would you test for in anaemic patients?
Serum ferritin, folate, B12 and iron
why would a patient have low iron levels and high serum ferritin levels?
Ferritin production is usually down-regulated when iron levels are low.
Elevated serum ferritin is possible with low iron because it is an acute phase reactant protein produced by the liver, and is elevated with inflammation/illness
In what ionic form is iron most commonly ingested, ferric or ferrous?
Most is ingested in the ferric form (Fe3+)
Ferrous iron = Fe2+
What ionic form of iron is absorbed in the GI tract?
Ferrous iron = Fe2+
Fe3+ is converted to Fe2+ by enzymes on the brush border or enterocytes = duodenal cytochrome b1
Where in the GIT does iron absorption occur?
Duodenum
How is iron transported into cells and what is its fate after this?
Fe2+ is transported into the enterocyte through DVMT 1 (divalent metal transporter 1)
It can then either be stored in the enterocyte as ferritin if body iron stores are high, or it can be transported out of the cell by ferroportin, a transported in the basolateral membrane
In plasma, Fe2+ is converted back to Fe3+, which binds to transferrin. It is then carried to sites such as the liver, bone marrow, and spleen
List the 4 main histological layers of the colon
1) mucosa
2) submucosa
3) muscularis externa
4) serosa
Where would you find auerbach’s plexus
= the myenteric plexus
between the circular and longitudinal layers of the muscularis externa
Describe the overall innervation of the intestine
innervated by the autonomic nervous system.
Parasympathetic cholinergic activity increases the activity of intestinal smooth muscle.
Sympathetic noradrenergic activity decreases the activity of intestinal smooth muscle, and causes sphincters to contract.
Parasympathetic fibres terminate on postganglionic neurons of the submucosal and myenteric plexuses
Sympathetic fibres are postganglionic neurons,. and end directly on smooth muscle cells
Which structures of the colon are retroperitoneal?
ascending colon
descending colon
rectum
Name retroperitoneal structures
adrenal glands kidneys ureters pancreas (except tail) IVC Aorta duodenum (partially) oesophagus (partially)
What is the blood supply of the ascending colon?
SMA = right colic artery and ileocolic artery
What is the commonest site of crohn’s disease?
terminal ileum
What are they symptoms of Crohn’s?
abdominal pain
malabsorption
weight loss
diarrhoea and bleeding if the colon is involved
Macrocsopically - cobblestone appearance (deep ulcers and fissures)
What are they symptoms of UC?
Diarrhoea with blood and mucous
Macroscopically the mucosa appears red and bleeds easily
Ulcers and pseudopolyps may be visible
disease process is continuous throughout the colon and rectum
Which colonic pathology can develop in patients who have longstanding IBD, especially UC?
colonic cancer/colonic adenocarcinoma
What is the surface marking of the fundus of the gallbladder?
Where the right side of the rectus abdominis muscle meets the costal margin (tip of 9th costal cartilage - although this is difficult to distinguish in clinical practice()
In surgery, what is Courvoisier’s law?
states that painless jaundice and a palpable gallbladder are rarely due to gallstones, but due to a tumour or other pathology
What causes itch in obstructive jaundice?
deposition of bile salts in the skin
How can you treat itch in obstructive jaundice?
cholestyramine
this is an anion exchange resin that binds to bile salts in the small intestine and blocks reabsorption, preventing enterohepatic recirculation
What do anion exchange resins do?
inhibit enterohepatic recirculation of bile salts
This indirectly lowers LDL cholesterol levels in the blood by increasing hepatic synthesis of bile acids, increasing LDL surface receptors as LDL is required for this.
Can be used in addition to statins
What would you expect to happen to albumin levels with obstructive jaundice?
decreased due to reduced synthetic function of the liver.
Albumin is only synthesised in the liver
What would you expect to happen to prothrombin time with obstructive jaundice?
increased
the liver is the site of clotting factor synthesis, and alll clotting factors except factor VIII are made in the lvier.
Vitamin K-dependent factors (II, VII, IX and X) may be deficient due to malabsorption of vitamin K
What is prothrombin time ?
predominantly a measure of the extrinsic clotting cascade
may be prolonged due to causes other than liver malfunction, e.g. vitamin K deficiency and warfarin therapy.
Which substances formed from bile pigments give stool its characteristic colour?
urobilinogen
stercobilinogen
What biochemical abnormalities are seen in the urine with obstructive jaundice?
low/absent urobilinogen
high urinary bilirubin (darkened urine)
Which region of the peritoneal cavity is the pancreas related to?
the lesser sac (omental bursa)
How is a pancreatic mass most likely to cause jaundice?
obstruction of the common bile duct, which runs posterior to or is embedded within the head of the pancreas
What is a common complication of ERCP?
acute pancreatitis
Which borders of the spleen contain notches?
anterior and superior
Which border of the spleen is palpable with splenomegaly?
superior border
moves inferomedially
What is a porto-systemic anastomosis
connection between the veins of the portal venous system, and the veins of the systemic venous system
What are the major sites of porto-systemic anastomoses
Oesophageal – Between the oesophageal branch of the left gastric vein and the oesophageal tributaries
to the azygous system.
o oesophageal varices
Rectal – Between the superior rectal vein and the inferior rectal veins.
o Haemorrhoids
Retroperitoneal – Between the portal tributaries of the mesenteric veins and the retroperitoneal veins.
Paraumbilical – Between the portal veins of the liver and the veins of the anterior abdominal wall.
o caput medusa
arterial supply of the duodenum
Proximal to the major duodenal papilla– gastroduodenal artery(branch of thecoeliac trunk).
Distal to the major duodenal papilla– inferior pancreaticoduodenal artery(branch ofsuperior mesenteric artery).
Meckel’s diverticulum
a slight bulge in thesmall intestine present at birth and avestigial remnant of the yolk stalk
how is the duodenum distinguished from jejunum and ileum histologically?
presence of brunner’s glands
Paneth cells
Found at the base of intestinal crypts
distinguished by their granular cytoplasm
Secrete granules of antimicrobial peptides called defensins, lysozyme and phospholipase A
not found in the large intestine
Which part of the intestine has the longest villi?
villi tend to be longest in the duodenum and shortest in the ileum
Which part of the small intestine has the most lymphoid tissue?
ileum
How does acute pancreatitis cause back pain?
the pancreas is a retroperitoneal organ
leakage of inflammatory exudate therefore leaks into the retroperitoneal space and lesser sac.
this causes irritation of reroperitoneal and pertioneal nerve endings
this produces intense back pain