CT Pathology

Extradural haemorrhage

blood collected between skull and dura mater due to injury to an intracranial artery

How does an extradural haemorrhage appear?

lens shaped collection pushing into the brain, blood is contained due to the dura’s connection to the skull at the sutures

What are the symptoms of extradural haemorrhage?

depends on which lobe affected and how much bleeding
decreased GCS - level of consciousness and wellness decreases as bleeding continues
headache
vomiting

Subdural haemorrhage

Venous bleeding that occurs between the dura and arachnoid layers due to a rupture to a bridging vein

How does a subdural haemorrhage appear?

crescent shaped collection causing mass effect and midline shift

What are the symptoms of subdural haemorrhage?

symptoms similar to extradural haemorrage but patient will not appear as sick
stroke like symptoms

What are the mechanisms of a subdural hemorrhage?

traumatic event e.g., fight

Subarachnoid haemorrhage

haemorrhagic stroke causing bleeding into the subarachnoid space and fourth ventricle allowing blood to mix with CSF

What are the mechanisms of subarachnoid haemorrhage?

spontaneous bleed from arteriovenous malformation or rupture of saccular/berry aneurysm

How does the bleeding in a subarachnoid haemorrhage progress?

bleed starts in circle of willis and mixes with CSF within meningeal layers that connect to brain and spinal cord

How does a subarachnoid haemorrhage appear?

star/spider shape, hyperdensity in areas CSF is located

When is a lumbar puncture required for a subarachnoid haemorrhage?

if CT negative but SAH still suspected, every patient with SAH symptoms must undergo a lumbar puncture

What are the symptoms of a subarachnoid haemorrhage?

thunderclap headache
nausea and vomiting
photophobia

What are the characteristics of a thunderclap headache?

sudden onset
reaches maximum intensity within seconds
10/10 pain

Intracerebral haemorrhage

haemorrhagic stroke causing bleeding within the brain due to a ruptured vessel (intraparenchymal or intraventricular)

How does intracerebral haemorrhage appear?

hyperdensity within the brain parenchyma, not confined by any dura

What are the mechanisms of a intracerebral haemorrhage?

hypertension
trauma - whiplash injuries, crashing to an immediate stop
AVM
drug abuse
brain tumours - primary or metastases

Ischemic Cerebral Vascular Accident (CVA)

reduced blood supply leading to brain tissue hypoperfusion

How does an Ischaemic CVA appear?

hypodensity caused by brain tissue dying off, clot in vessel can appear hyperdense

What are the mechanisms of ischmaemic CVA?

embolism
thrombosis
systemic hypoperfusion
cardiac arrest
hypoxia

What are the possible treatments for ischaemic stroke?

thrombolysis
thrombectomy
antiplatelets and anticoagulants

Thrombolysis

administration of medicine that dissolves clots

When can thrombolysis be performed?

if stroke occurred under 4 hours ago
cannot be used if stroke is haemorrhagic, history of bleeding, on medication contraindicated

What complication can thromobolysis cause?

haemorrhagic stroke

Thrombectomy

interventional procedure involving mechanical removal of clot

When can thrombectomy be performed?

if stroke occurred six and half hours after stroke
can only be done at a stroke centre

Antiplatelets and Anticoagulants

blood thinners
antiplatelets make blood less sticky by decreasing production of platelets
anticoagulants prevent clotting

When are antiplatelets and anticoagulants be given?

if outside time limit for other treatment (thrombolysis/thrombectomy)

Transient Ischemic Attack (TIA)

temporary disruption in blood supply to part of brain, warning sign for larger stroke.

What are the symptoms of TIA?

stroke like symptoms
speech/visual disturbance
numbness/weakness in face/arms/legs

How long do symptoms of TIA last?

symptoms last 24 hours before resolving

How does an abscess in brain appear?

hyperdense ring with central low attenuation, focal area of necrotic tissue around abscess

Pulmonary embolism

occlusion of pulmonary vessels (usually arteries) in lungs, usually caused by blood clots that arise from deep vein thrombosis in legs, can cause lung infarct

What examination is used to image pulmonary embolism?

CXR to rule out infection and other causes
CT Pulmonary Angiogram (CTPA)

CTPA contrast protocol

75ml @ 4.5-5ml/s followed by saline chaser, requires large cannula

How does pulmonary embolism appear on CT?

clots seen as filling defects as contrast cannot fill areas occupied by clots
good opacification in pulmonary arteries
no contrast in descending aorta
some contrast left in ascending

What else can be used to diagnose pulmonary embolism?

Wells score more than 4
D-dimer test
RNI imaging for pregnant women

Pneumothorax

abnormal collection of air in the pleural space, leading to lung collapse

How does pneumothorax appear?

pocket/rim of air located outside lung and adjacent to chest wall, most commonly in apices
associated lung collapse
only visible on lung window

Why is CT used to identify pneumothorax?

identifies small pneumothoraxes missed by CXR, shows more about surrounding tissue if cause unknown

What is the treatment for pneumothorax?

reinflation with chest drain

Acute Ischemic Stroke

sudden loss of blood flow to an area of the brain resulting in tissue damage caused by clot or embolism

Hyperdensity in CT scans

increase in density appearing brighter on a CT scan, indicating fresh blood or solid structures

Liver Metastasis

cancerous tumour cells that has spread to liver from cancer in another place in body usually from cancerous breast, colon or lung cells, secondary liver cancer

What examination is used to diagnose liver metastases?

CT with contrast in portal venous phase

Portal Venous Phase contrast protocol

contrast injected @ 3ml/s, 70 second delay

How does liver metastases appear on non contrast CT?

multiple low attenuation density lesions

How does liver metastases appear on contrast enhanced CT?

multiple low attenuation metastases
liver enhances normally but metastases do not
hyperdensity around metastases

Lumbar puncture

procedure to collect cerebrospinal fluid for analysis

Contrast enhancement

increase in visibility of structures after administration of contrast material

Mass effect

Displacement of brain structures due to space-occupying lesions.

Berry aneurysm

A small, sac-like outpouching that occurs on the walls of a blood vessel in the brain.

Neuroimaging

techniques used to visualise structure and function of nervous system

Abdominal Aortic Aneurysm (AAA)

localised enlargement of abdominal aorta, diameter greater than 3cm or more than 50% larger than usual

What are the symptoms of AAA?

back pain 
pulsating abdominal mass  
acutely unwell patient, unstable vital signs 

What are possible complications of AAA?

high mortality rate up to 90%
severe internal bleeding
hypovolemic shock
low BP
unconsciousness

What examination is used to diagnose AAA?

CT aortogram

CT aortogram contrast protocol

75ml @ 4.5-5ml/s, bolus tracked, imaging taken on arrested respiration

What is the area of interest for CTA?

clavicles to groin
groin imaged to visualise femoral artery where intervention can start from

What population is screening for AAA available to?

all men over 65 years, ultrasound used

What is used to treat AAA?

anastomoses - surgically sewing aorta back together
EVAR - endovascular aortic repair, repairs leaks or infections of graphs

Haemorrhagic stroke

type of stroke caused by bleeding within the brain, aneurysm or blood vessel ruptures

Urolithiasis

renal stones, presence of calculi anywhere along course of urinary tract

What are the symptoms of urolithiasis?

flank pain
vomiting  
haematuria due to large stone scraping against walls of small vessel 
high temperature/fever 

What examination is used to diagnose urolithiasis?

non contrast CT KUB prone/supine
contrast not used as stones also appear hyperdense

Hydronephrosis

enlarged kidney due to obstruction or other pathology

What examination is used to diagnose hydronephrosis?

ultrasound
CT abdomen
PV abdomen - to rule out cause being pelvic malignancy

CT Urogram contrast protocol

150ml @ 3ml/s with saline chaser, 7-11 minute delay

PV Abdomen contrast protocol

75ml @ 3ml/s with saline chaser, 78 second delay