Week 4 Flashcards
(125 cards)
1
Q
How can fluid be lost in the body?
A
Urine, faeces, expired air, sweating, insensible losses
2
Q
What do Na+ co-transporters transport?
A
Amino acids, peptides, bile salts and vitamins
3
Q
Tight junctions of enterocytes are permeable to substances with a molecular weight of what?
A
<300 daltons
4
Q
What must accompany Na when given orally in order to allow its absorption?
A
Glucose
5
Q
What does the SGLT1 transporter do?
A
Allows Na+ and glucose to enter the cell (leave lumen)
6
Q
What does the GLUT2 transporter do?
A
Allows glucose to leave the cell (enter blood)
7
Q
Which molecules are able to passively move between enterocytes?
A
Cl- and H20
8
Q
What pathogens cause cholera and what is their mechanism of disease?
A
Vibrio cholerae and Eschericia coli
Enterotoxin release → β2-adrenoceptor → activation of cAMP → PKA → activation of CFTR channel → massive chloride secretion
9
Q
What are the 3 types of diarrhoea?
A
Secretory, inflammatory and osmotic/malabsorptive
10
Q
Outline the main features of secretory diarrhoea
A
Causes - acute infection (E.coli), failure of bile salt absorption, fat malabsorption, laxative abuse, carcinoid syndrome, Zollinger-Ellison syndrome
Mechanism - destruction of tight junctions, allowing water to leak from enterocytes
Decreased absorption, increased secretion, high volume
11
Q
Outline the main features of inflammatory diarrhoea
A
Causes - IBD, Crohn’s, ulcerative colitis, infection (Shigella, Salmonella)
Increased secretion and propulsion of bowel, low volume
12
Q
Outline the main features of osmotic diarrhoea
A
Causes - laxatives, antacids, orlistat, digestive enzyme deficiency, pancreatic insufficiency, inflammatory disease, short bowel syndrome
Decreased absorption, high volume
13
Q
How is diarrhoea in children treated?
A
Fluid replacement - oral rehydration salts
Zinc supplements - decrease severity and duration
Continue feeding, increase fluids
14
Q
What factors does speed of fluid replacement depend on?
A
Age
Renal function
Cardiovascular status
(severity and time taken to develop dehydration)
15
Q
What are the 3 main body fluid compartments?
A
Intracellular - intracellular fluid
Extracellular - interstitial fluid, intravascular fluid
16
Q
What is the consequence of high and low osmolarity?
A
High - cellular dehydration
Low - cellular oedema
17
Q
What are the 3 types of IV solutions available?
A
Blood products
Colloids (albumin, hydroxyethyl starch)
Crystalloids (saline, dextrose, Ringer-lactate, Hartmann’s)
18
Q
How would you describe the osmolarity of 0.9% saline?
A
Iso-osmotic
19
Q
What is the standard regimen of saline and dextrose?
A
2:1
20
Q
What percentage of colloids, saline and dextrose actually remain intravascular after infusion?
A
Colloids - 100%
Saline - 25%
Dextrose - 10%
21
Q
What is the function of lactate-containing IV fluids?
A
Normal saline may cause acidosis; lactate metabolism produces HCO3 which protects against this
May cause cerebral oedema
22
Q
What is the volume of a standard bag of IV fluids?
A
500ml
23
Q
What fluid regimen is typically used in emergency re-hydration?
A
1 bag every 2 hours
6L over 24 hours
24
Q
What fluid regimen is typically used as standard?
A
1 bag every 6 hours
2L over 24 hours
25
What fluid regimen is typically used in slow rehydration?
1 bag every 8 hours
| 1.5L over 24 hours
26
What is the maximum concentration and rate of K+ supplementation?
Concentration - 40 mmol/L
| Rate - 10 mmol/hr (up to 20 with cardiac monitoring/central line)
27
What cardiac safeguards are needed for K+ supplementation in hypokalaemia?
Baseline ECG if K <3 mmmol/L
| Cardiac monitoring if K <2.5 mmol/L or giving faster than 10 mmol/L
28
What are the ECG features of hypokalaemia?
Slightly prolonged PR interval, peaked P wave, ST depression, shallow T wave, prominent U wave
29
What is the normal range of K+ in the body?
3.5-5.0 mmol/L
30
What are the ECG features of hyperkalaemia?
Tall peaked T wave, loss of P wave, widened QRS complex
31
What is the anatomical position of the spleen?
High on the left side of the body
Left hypochondria
Directly under the diaphragm
Posterior to the mid-axillary line
32
Where does the transverse mesocolon attach to the pancreas?
Inferior border
33
Where is the stomach situated in relation to the duodenum and pancreas?
In front
34
At what vertebral level is the head of the pancreas seen?
L2, extends upwards to L1
35
What are the components of the duodenum and what are their lengths?
Superior - 5 cm
Descending 7.5 cm
Horizontal - 10 cm
Ascending - 2.5 cm
36
Where is the ampulla of Vater found?
2/3rds down the descending portion of the duodenum
37
What blood vessel lies behind the neck of the pancreas?
Portal vein
38
How are the superior mesenteric artery and vein arranged?
Run alongside one another
| Artery on the left of the vein
39
Outline the anatomy of the superior mesenteric artery
Comes directly off the aorta
Directly posterior to the body of the pancreas
Runs in front of the uncinate process of the pancreas
40
What is the uncinate process of the pancreas?
An elongated 'hooked' portion of the caudal portion of the head of the pancreas
41
What are the 3 specific branches of the coeliac trunk?
Left gastric artery - supplies oesophagus and proximal lesser curvature of stomach
Common hepatic artery - gives rise to the right gastric artery, supplies distal lesser curvature of stomach and head of pancreas, also gives hepatic and cystic arteries
Splenic artery - twisted
42
How can the size of the spleen be described?
Size of a fist
43
What does the splenic artery supply and how many branches does it have?
Spleen (and pancreas)
| 5-6 branches
44
Why is the splenic artery tortuous?
Reduction of blood pressure to allow continuous supply to the delicate spleen
45
What causes portasystemic anastomoses and how?
```
Portal hypertension (e.g. due to cirrhosis)
Attachment of the portal venous system to the general veins of the body
```
46
What areas are most affected by portasystemic anastomoses?
Oesophagus - azygous vein and left splenic vein; varices
Anal canal - internal iliac vein and rectal veins; haemorrhoids
Umbilicus - falciform ligaments have vessels which are enlarged causing caput medusae (distension of umbilical region veins)
47
What are the tributaries of the portal vein?
Splenic vein, superior mesenteric vein and inferior mesenteric vein
48
What artery supplies the hindgut?
Inferior mesenteric artery
49
Which vein drains into the right lobe of the liver and why?
Superior mesenteric vein - more nutrients/toxins to be metabolised/detoxified
50
Which vein drains the left lobe of the liver and why?
Inferior mesenteric artery - contains mostly water, smaller liver lobe
51
What is the clinical significance of the splenic notch?
Can be palpated in splenomegaly
52
What is cholecystitis?
Inflammation of the gallbladder
53
What is cholelithiasis?
Gallstone (within gallbladder)
54
What is cholecystectomy?
Removal of gallbladder
55
What is choledocholithiasis?
Gallstone (within bile duct)
56
What is cholangitis?
Infection of bile duct
57
What is MRCP?
Magnetic resonance cholangiopancreatography
58
What is ERCP?
Endoscopic retrograde cholangiopancreatography
59
What is PTC?
Percutaneous transhepatic cholangiography
60
Outline the anatomy of the biliary tree
Biliary canaliculi → interlobular bile ducts → septal bile ducts → intrahepatic ducts → R/L hepatic duct → common hepatic duct (joins with cystic duct) → common bile duct (joins with pancreatic duct)
61
Where does the common bile duct pass?
Behind duodenum, through head of pancreas, into 2nd part of duodenum
62
What is the capacity of the gallbladder?
30-50 mls
63
On what surface of the liver does the gallbladder sit?
Right inferior
64
What are the 3 parts of the gallbladder?
Fundus, body, neck
65
What is the composition of bile?
```
Bile acids
Water
Electrolytes
Cholesterol
Phospholipids
Conjugated bilirubin
```
66
How is bile formed?
Cholesterol → cholic acid and chenodeoxycholic acids (primary) → conjugation to secondary by taurine/glycine addition
67
How does gallbladder contraction cause bile secretion?
Vagus - gallbladder contraction
CCK (fat in duodenum) - gallbladder contraction, sphincter relaxation
Sympathetics, VIP and somatostatin - gallbladder relaxation
68
What are the functions of bile acids?
Emulsification of fats
Facilitation of fat soluble vitamins
Facilitation of cholesterol excretion
Influence intestinal metabolic pathways
69
What percentage of bile acids are reabsorbed and where does this mainly occur?
95% (5% faecal loss)
| Ileum
70
What are the 5 F's of gallstone risk factors?
```
Female
Fair
Fertile
Forty
Fat
```
71
What types of gallstones are there?
Cholesterol stone - solitary, large, oval
Bile pigment stone - multiple, irregular, hard (chronic haemolysis)
Mixed stones - most common (80%), laminated, multiple
72
What are the 3 main events which lead to gallstone formation and in what order do they occur?
Cholesterol supersaturation
Biliary stasis
Increased secretion of bilirubin
Often occur simultaneously
73
What is cholesterol supersaturation and how does it occur?
Cholesterol highly concentrated
Due to very high levels of cholesterol, usually when oestrogen is high (obesity, pregnancy, OCP, liver disease) and bile acids are low (small bowel resection, Crohns)
74
What is biliary stasis and how does it occur?
Bile cannot flow from the liver to the duodenum
| Due to periods of fasting, starvation or prolonged total parenteral nutrition
75
How does increased secretion of bilirubin occur in gallstone formation?
Due to increased RBC breakdown (e.g. sickle cell, malaria, valvular heart disease, post-chemotherapy) or failure of hepatic conjugation
76
What complications can arise from gallstones in the gallbladder, common bile duct and small intestine?
Gallbladder - biliary colic, acute cholecystitis, empyema, mucocoele, cancer
Common bile duct - obstructive jaundice, cholangitis, pancreatitis
Small intestine - gallstone ileus
77
What is biliary colic, what are its associated symptoms and how is it treated?
Pain in the epigastric region caused by temporary blockage of the bile duct usually provoked by eating
Vomiting common; no jaundice/fever/LFT abnormalities
Can resolve if stone moves back into gallbladder, surgical removal of gallbladder if recurrent
78
What is acute cholecystitis, what are its associated symptoms and how is it treated?
Impacted stone causing oedema, inflammation and development of bacterial infection in gallbladder wall
Pain, nausea, vomiting, fever, abdominal tenderness; raised inflammation markers, abnormal LFTs, jaundice
Antibiotics, analgesia, gallbladder removal when symptoms settle
79
How can post-hepatic obstructive jaundice be caused?
Common - gallstones in bile duct, head of pancreas tumour
| Less common - pancreatitis, cancer of bile duct, portal lymphadenopathy, bile duct stricture
80
What are the symptoms of obstructive jaundice?
```
Pale stool
Dark urine
Yelow sclerae
Itching
Chronic liver disease features
Possible hepatomegaly and abdominal tenderness
```
81
How would obstructive jaundice due to a gallstone in the bile duct be treated?
Ultrasound/MRCP to confirm diagnosis
ERCP to remove stone
Cholecystectomy to prevent recurrence
82
What LFTs are associated with hepatocytes?
AST/ALT
83
What LFTs are associated with bile duct cells?
ALP/GGT
84
What would LFTs show in biliary obstruction?
```
ALP - increased early (10x)
GGT - increased
Bilirubin - steady rise, level indicative of duration
AST/ALT - elevated transiently
Coagulopathy
```
85
What would LFTs show in viral hepatitis/paracetamol overdose?
ALT/AST - greatly increased
ALP/GGT - slightly/not increased
Bilirubin - increased
86
What affect does dehydration have on the glomerular filtration rate and tubular luminal flow and how can this be measured indirectly?
Both decreased
| Urea will be increased
87
Why must any history of cardiac disease be checked before starting IV fluids?
Patients with left ventricular dysfunction can develop pulmonary oedema if too much fluid is given too quickly
88
What 3 factors must be taken into account when calculating how much IV fluid is required over 24 hours?
Measured losses - urine/vomit/diarrhoea/drains
Insensible losses - skin/respiration/perspiration/ventilation
Previous day deficit - subtraction of the previous day's fluid intake from sum of losses
89
How is fluid required over the following 24 hours calculated?
Measured losses + insensible losses + previous day deficit
90
Over what length of time can the previous day's deficit be replaced?
2-3 days (cardiac disease)
91
What are the 2 main crystalloid fluids prescribed and when are they used?
5% dextrose - metabolised to CO2 and water, water replacement only
0.9% saline - physiological NaCl, electrolyte and water replacement
92
What is a normal fluid intake?
1.5 L/day
93
What is the minimum daily K loss?
60-80 mmol/day
94
How much KCl can be added to a 500ml bag of saline?
20 mmol
95
Why is hypokalaemia associated with cardiac arrhythmia?
K is the main intracellular ion involved in heart conduction
96
Why might a patient present with hypotension and tachycardia?
Dehydration
Sepsis
Hypovolaemic shock
Burns
97
What is a normal urine output?
30 mls/hour
98
What are the symptoms of fluid loss?
```
Pale skin
Hypotension
Tachycardia
Postural hypotension
Raised JVP
```
99
Why would a decrease in Mg affect Na and Ca?
Mg is a co-factor for Na+/K+ ATPase on the kidneys (required for Na+ excretion) and Ca2+ release (PTH from parathyroid gland)
100
What is the normal ratio of saline to dextrose prescribed?
2:1
101
What factors ensure the upper gut is almost sterile?
Gastric acidity
Propulsive motility
Pancreatic enzymes
102
What effect do SCFAs have on diarrhoea?
Prevent osmotic diarrhoea by promoting water absorption
103
What are probiotics?
Live microbial food supplements which benefit the host by improving intestinal microbial balance
104
What are the potentially harmful products of bacterial fermentation?
```
Carcinogens and toxins
Azo dyes
Phenols
Hydroxy fatty acids
Secondary bile acids
```
105
Name the main SCFAs and their functions
Acetic acid - substrate for hepatic fat synthesis
Propionic acid - hepatic glucose production, reduction of cholesterol synthesis
Butyric acid - stimulation of cancer cell differentiation and programmed cell death
106
What are prebiotics?
Fermented ingredient which results in changes to the composition/activity of microbiota, conferring benefit to the host
107
How do colonic bacteria inhibit pathogens?
Produce antibiotics
Compete for binding sites
Create physical barrier
108
What is small bowel overgrowth?
Increased number of bacteria lodge in mucosa and ferment foodstuffs usually digested to produce alcohol and lactic acid; may give patient drunken appearance
109
What is lactulose?
An unabsorbable sugar used to treat constipation by softening stool
110
What is the fluid circuit hypothesis?
Absorption from the villous tips usually exceeds fluid secretion from villous crypts = net absorption
Loss of absorptive capacity due to cell damage/enterotoxins = net secretion = diarrhoea
111
What is the pathological mechanism of C.difficile enterotoxin?
Epithelial cells fall off the mucosa, leaving spaces for fluid to be extruded
112
What is the pathological mechanism of E.coli heat stable enterotoxin?
Inhibition of enterocyte fluid absorption
113
What is the pathological mechanism of V.cholerae?
Inhibition of enterocyte fluid absorption and ZOT loosens tight junctions and causes intestinal vasodilation
114
What are the mechanisms by which diarrhoeal disease can be caused?
Interruption of enterocyte fluid absorption
Loss of intestinal epithelial cells
Loosening of binding between epithelial cells
Chloride ion and fluid secretion by enterocytes
115
What can be caused by sustained diarrhoeal disease?
Hypokalaemia (loss of K in stool)
| Acidosis (loss of bicarbonate in stool)
116
Where are secretory cells of the small intestine found?
Crypts of Lieberkühn
117
How is diarrhoea defined?
3 or more loose/watery stools per day
118
What complications can arise from Campylobacter infection?
Guillain-Barre - demyelinating neuropathy
119
What complications can arise from E.coli 0157 infection?
Shiga toxin - vascular haemolysis, renal failure, haemolytic uraemic syndrome
120
What complications can arise from C.difficile infection?
Pseudomembranous colitis, toxic megacolon, perforation
121
What 2 bacteria are highly infectious, have a low infectious dose and require contact tracing/further investigation?
E.coli 0157
| Salmonella typhi
122
What important vitamin is made and absorbed in the large intestine?
Vitamin K
123
Which artery does the superior rectal artery originate from?
Inferior mesenteric artery
124
Which age group is at highest risk of chronic hepatitis B infection?
Neonates
125
Which nerve supplies the internal anal sphincter?
Hypogastric plexus
