Investigations

Question 1

General radiology

Answer 1

Stored in DICOM, Picture Archiving and Communication System

Checks:

1. Name
2. Date
3. Relevant images are there
4. Orientation - metal mark on the left

X-ray
Bone (white) -> Air (black), talk about density
Examples: CXR, AXR, extremity radiographs, mammography
Adv: low dose (NB background), quick, cheap
Disadv: Poor for soft tissue, poor sensitivity and specificity

CT
X-ray tubes and detector - 3D and reconstructed in any plane
Talk about attenuation
Examples: Head injury, acute abdomen, abdo trauma, staging cancer.
Adv: Spatial resolution, sensitive and specific, 3D
Disadv: Ionising rad, iodine contrast => nephrotoxicity, cost and high data load

US
2-15MHz - emit and receive
Examples: pregnancy, brain (neonate), soft tissue, PVD, DVT, abdomen and pelvis
Adv: Portable, non-invasive, not ionising
Disadv: Operator dep, limited depth penetration and anatomical access

MRI
Field alligns to protons and produces an RF signal on returning to rest, depending on the proton content and surrounding milieu
Examples: MSK, neuro, liver, gynae, prostate
Adv: no ionising, soft tissue differentiation, Gadolinium instead of iodine contrast
Disadv: Artefacts (movement), patient unsuitability, less spatial resolution than CT, time and cost

Nuclear Medicine
Radiation source inside the patient, combined with a metabolic function
Examples: V/Q scan, bone scintigraphy, PET-CT
Adv: sensitivity, functional, quantifiable
Disadv: ionising radiation, low specificity, time, spatial resolution

Interventions
Vascular - angioplasty, stent inserting, EVAR (Endovascular aneurysm repair) stent
Non-vascular - liver and biliary tract, GI and urinary tract

Ionising rdiation
ALARA
Background - 2.64mSv/year. X-ray (day) to PET-CT (a few years)

Contrast
Provides higher density to highlight its route.
Barium - GI tract investigation
Risk:
peritonitis if it spills into peritoneal cavity
Iodine - for CT intravascular agent
Injection leads to hot flush and feeling a need to urinate
Risks:
Allergic reaction
Nephropathy - NB susceptibility of renal patients
Gadolinium - MRI (alters the magnetic properties between tissues)
Risks:
Nephrogenic systemic fibrosis (NSF) (reminiscent of scleroderma)
Dentate Nucleus and Globus Pallidus accumulation

Question 2

Bloods

Answer 2

In general:
Assist in diagnosis 
Screening 
Evaluate prognosis
Monitoring

Different levels
1)
FBC
U&Es
LFT
BFT
CRP
ESR

2)
Folate
Iron Stores
Vitamins

3)
Auto-antibodies
Tumour markers
Genetic tests
Viral serology

Question 3

ECG principles

Answer 3

Measure the electrical activity at the surface, used to infer the vectors of conduction in the heart

Dimensions
1mV = 10mm
Whole page is 10s

Affected by
Electrolyte disturbances
IHD
Hypertrohpy

Common indications
Chest pain
SOB
Palpations

How it is performed

10 electrodes -> 12 leads

4 arm
6 chest

Approach

Patient ID, indications, calibration

Rate - 300/small squares, 6x number of complexes on the rhythm strip

Rhythm - Reg, Reg Irreg, Irreg Irreg
Sinus - P followed by QRS
AF - no P and irreg irreg QRS
A Flutter - sawtooth, atrial rate of 300/min
Ventricular - QRSs >120ms

Axis - overall direction of the (ventricular) depolarisation
Normal = -30 to +90, then left deviation is 90
1) If I and aVF +ve then normal
2) If I +ve and aVF -ve, check II. If this is +ve then it is normal
3) Look at I and III.
Leaving = LAD
Returning = RAD

P wave - atrial origin
Normally:
Up - II, III, aVF
Inverted - aVR
If absent: AF or hidden due to junctional or ventricular rhythm
If bifid (mitrale): suggestive of Left Atrial Hypertrophy
If peaked (pulmonale): suggestive of Right Atrial Hypertension or elevated K

PR - start of P to start of QRS
Normal - 0.12-0.2
Prolongation suggests AV delay (first degree heart block)
Shortening suggests bypassing pathways e.g. WPW

QRS
Normal <0.12, indicates it is going through the bundles
Prolongation - BBB, metabolic disturbances, ventricular originating
High amplitude - ventricular hypertrophy
Deep (>2mm) and wide (>0.04) Q - post acute MI

QT - start of QRS to end of T
Can vary with rate therefore take corrected
LQT - can lead to VT and death - various causes

ST
Usually isoelectric
Elevated (>1mm in 2 or more limb or >2mm in 2 or more chest) - infarction
Depression (<0.5mm) - ischaemia

T wave
Inverted in aVR, V1 and V2 (or in III in isolation) is normal
Inversion in I, II, V4-6 is abnormal (e.g. following PE)
Tented in hyperkalaemia

J wave - S finish to ST starts
Seen in hypothermia, SAH (subarachnoid haem) and elevated Ca
`

Question 4

FBC

Answer 4

Level one bloods

NB Artefacts

RBC

Red blood cell (RBC) count - 4.20-5.80 10*12/L
Haemoglobin (Hb) - 130-170 g/L
Mean cell volume (MCV) - 80.0-100.0 fL
Mean cell haemoglobin (MCH) - 27.0-32.0 pg

Outcome
• Low RBC / Hb - Anaemias
• High RBC / Hb - Polycythaemia

Cues to:
• Alcohol use
• Kidney disease
• Liver disease
• Sickle cell disease / thalassaemia

Hb range
Men: Hb 130-170g/l
Women: Hb 115-160g/l - menstruation, muscle mass difference, testerone (effects on erythropoetin)

Low Hb

MCV
Microcytis - Iron def 
Cause:
Dietary
Malabsorptive 
Chronic blood loss
Further investigation:
Ferritin and Total Iron Binding capacity

Normal but with Low Hb
Anaemia of chronic disease
Haemolysis
Renal failure
Myeloma

Macrocytis
Folate/B12 def
Liver disease
Myelodysplasia

High Hb - Polycythaemia
Induced by hypoxia:
Smoking (carbon monoxide bound to Hb)
Altitude
COPD
Renal path:
Polycystic kidney disease
Renal tumours

WBC

Leucocytosis = rise
Causes:
Infeciton
Autoimmune
Traumatic injury
Leukaemia

Leucopaenia = fall
Drugs
Early leukaemia
Blood dyscrasias
B12 def

Cell subtypes

Neutrophils
Bacterial infection 
Acute phase response
Auto-immune damage
Inflammation

Lymphocytes
Viral infections

Eosinophils
Asthma
Allergic reactions

White blood cell (WBC) count - 4.0-11.0 109/L
Neutrophil count - 2.00-8.00 109/L
Lymphocyte count - 1.00-4.50 109/L
Eosinophil count - 0.00-0.40 109/L

Clotting indices
Use - assess risk of bleeding and pre-procedures
Basis - Vascular, platelet and coagulation phases

Problems:
Inherited
Acquired
Drug therapy

Measures:
Platelet Count - 150-400 10*9/L 
Prothrombin time (PT)
International Normalized ratio (INR)
Partial thromboplastin time (PTT)

PT - time for citrated plasma to clot on addition of TF and Ca
Extrinsic and common pathways
Measures: def in Factors V / VII / prothrombin / fibrinogen
Prolonged in: Warfarin use, Cirrhosis and decomp LF

aPTT - time for citriated plasma to clot on addition of kaolin and Ca
Intrinsic and common pathways
Measures: def in V / VIII to XII / prothrombin and fibrinogen
Prolonged in: Haemophilia

Low count - thrombocytopenia
Decreased production:
Marrow suppression
Leukaemia
Viral infection
Drugs
Increased destruction:
Idiopathic thrombocytopenia purpura (ITP)
Hypersplenism

Question 5

Inflammation markers

Answer 5

Level one bloods

ESR - 2-10mm
CRP - 2-10mm

ESR - Erythrocyte sedimentation rate
How far RBC in a column of blood fall in one hour
NB NOT SPECIFIC - instead it is a surrogate marker
It changes in inflammation or anaemia due to increased fibrinogen / upregulation of CAMs etc.

High in:
1. Myeloma
2. SLE
3. Temporal arteritis
4. Polymayalgia rheumatica
Rarely: carcinoma/chronic infection

CRP - C-Reactive Protein
Marker of tissue injury
NOT SPECIFIC - bacterial or auto-immune
If over 100, likely to be bacteria

Question 6

LFTs

Answer 6

To access liver function and toxicity of drugs

Albumin - 35-50 g/L
Total Bilirubin - 0-20 umol/L
Alkaline Phosphatase - 30-130 U/L
Alanine Transaminase - 7-40 U/L

Albumin
Functions:
Provides plasma oncotic pressure
Source of protein for metabolic functions
“Chaperone” for other chemicals - calcium

Hypoalbuminaemia:
Liver disease – impaired synthetic function
Inflammation – liver switched to CRP synthesis
Malnutrition
Nephrotic syndrome – urinary loss of protein

Bilirubin
Product of RBC recycling
Harmful; not very soluble
Modified by liver enzyme UGT1A1 (UDPglucuronosyltransferase1A) which transforms it from a lipophilic molecule into a water-soluble
excretable metabolite - Conjugated or “direct” bilirubin

Elevation (>35) => Jaundice
1. Pre-hepatic - haemolysis, congential
2. Hepatic - alcohol, viral, drugs, autoimmune, heritable, neoplastic
3. Post-hepatic
Benign - gallstones, cholangitis, biliary stricture
Malignant - pancreatic cancer, cholangiocarcinoma

Alkaline phosphatase (ALP)

The point of this is that it is meant to be an intracellular enzyme
Found in biliary tree and bile ducts BUT also found in bone and placenta

Elevated:
• Liver disease (cholestasis / obstructive jaundice)
• Bone disease (osteoblast activity)
• Pregnancy

Alanine Aminotransferase (ALT)

Similar to above - Intracellular liver enzyme

Elevation:
Hepatocellular damage:
Active hepatitis - viral, alcohol, drugs, toxins
Ischaemic injury
Liver enzyme induction 
Drugs - e.g. statins induce it
Toxins

Question 7

U&Es

Answer 7

Level 1 bloods

Marker of kidney function

Serum Sodium - 133-146 mmol/L
Serum Potassium - 3.5-5.3 mmol/L
Serum Creatinine - 62-115 umol/L
Serum Urea - 2.5-7.8 mmol/L
Estimated GFR - 90-125ml/min
Serum Bicarbonate - 22-29 mmol/L

NB eGFR is a better measure the sCr alone (taking into account sCr, age, sex, gender, race)

Urea 
Elevated
Renal disease
Dehydration
Upper GI bleed
Steroids

Sodium
Primary (extracellular) electrolyte
Independ of ECF vol
Alterations in serum sodium reflect alterations in either sodium OR water. 
Hyponatraemia = serum sodium <133mmol/l
Hypernatraemia = serum sodium >146mmol/l

Low Na
Hypovolaemia - dehydration, extrarenal loss (GI tract, burns), diuretics, Addison’s
Euvolaemia - drugs, malignancy, pulmonary disorder, neurological disorders
Hypervolaemia - Cardiac failure, renal failure, nephrotic syndrome, cirrhosis

Potassium

Primary intracellular electrolyte
Hyperkalaemia = serum potassium >5.3mmol/l
Hypokalaemia = serum potassium <3.5mmol/l
NB Cardiac dysrhythmias - but may be asymptomatic until point of arrest
NB to check potassium after giving ACEi

Hyperkalaemia
Causes:
Potassium retention
1. Renal failure
2. Decreased mineralocorticoids
Addison’s
Spironolactone
ACEi / ARB
3. Potassium-sparing diuretics
Amiloride
Potassium release from intracellular space
Haemolysis
Trauma
Cytotoxic therapy for malignancy

6 ECG changes
Tented T waves
Prolonged PR
Reduced amplitude of P wave
Widening of QRS
Sinusoidal rhythm
VF/VT or asystole

Treatment
10ml CaCl 10% IV (5min)
50ml Dextrose 50% with 10 units of soluble insulin IV (NB NaKATPase)
Stop drugs ACEi
Consider dialysis

Hypokalaemia 
GI loss
Diarrhoea and vomiting
Renal loss
1. Diuretics – loop / thiazides
2. Mineralocorticoid excess (Conn’s, Cushing’s Steroid therapy)
3. Poor intake
4. Shift to intracellular compartment (insulin)