Physiology & Pathology Flashcards
How and where is CSF produced?
Produced by arterial blood from the choroid plexus of lateral and fourth ventricles via diffusion, pinocytosis and active transfer
Where is CSF absorbed?
Arachnoid villi into venous circulation
What correlates with CSF pressure?
Rate of CSF absorption
What happens to the heart during diastole?
Ventricular filling, atrial contraction
What happens to the heart during systole?
Ventricular contraction, atrial filling
What is the role of the portal vein?
Deliver venous blood to the liver for processing of nutrients and by-products of food digestion
What is the percentage of blood supplied to the liver by the portal vein and hepatic artery?
80% portal vein, 20% hepatic artery
What is the role of the hepatic artery?
Supply oxygenated blood to the liver
What is the role of the hepatic vein?
Drain deoxygenated blood from the liver into the IVC
Where is blood found in a subdural haemorrhage?
Between arachnoid and dura mater
What is the cause of subdural haemorrhage?
Stretching of bridging cortical veins crossing the subdural space
What is a cause of spontaneous subdural haemorrhage?
Anticoagulation medication or arteriorvenous fistula
Where is blood found in an extradural haemorrhage?
Between inner surface of skull and outer layer of dura mater
What is usually the source of bleeing in extradural haemorrhage?
Middle meningeal artery
Where is blood found in a sub-arachnoid haemorrhage?
Subarachnoid space
What are the risk factors of a sub-arachnoid haemorrhage?
Family history, hypertension, heavy alcohol consumption, abnormal connnective tissue, female
What are the symptoms of a sub-arachnoid haemorrhage?
Thunderclap headache, photophobia, miningism, focal neurological deficits
What the the name of the scale to predict survival in sub-arachnoid haemorrhage?
Hunt and Hess scale
What are the common causes of sub-arachnoid haemorrhage?
Ruptured berry aneurysm, perimesencephalic haemorrhage
Where are the common locations of intracerebral haemorrhage?
basal ganglia, diencephalon, thalamic, pontine, cerebellar, lobar
What condition and pathological process commonly causes intracerebral bleeds?
Hypertension due to pathological changes in the vessels
Describe communicating hydrocephalus with obstruction
CSF can exit the ventricular system but flow is impeded between the basal cisterns and the arachnoid granulations
Describe communicating hydrocephalus without obstruction
Group of conditions abnormal CSF dynamics e.g. normal pressure hydrocephalus and choroid plexus papillomas
Describe non-communicating hydrocephalus
CSF cannot exit the ventricular system resulting in dilated ventricles causing mass effect
Describe what happens physiologically when a stroke occurs
Interruption of blood flow results in deprivation of oxygen and glucose in the supplied vascular territory resulting in cellular death via liquefactive necrosis if circulation is not re-established in time
What are the 3 causes of a stroke
Embolism, thrombosis, arterial dissection
In the stroke setting why is CT Brain used?
To exclude intracranial haemorrhage which would preclude thrombolysis, look for ‘early’ features of ischaemia and to exclude other pathologies such as tumor
What is the timing for early hyperacute stroke and what are the features?
Time:0-6 hours
Loss of grey-white matter differentiation and hypoattenuation of deep nuclei
What is the timing for acute stroke and what are the features?
Time: 24hr-1 week
Hypoattenuation and swelling become marked resulting in mass effect
What is the timing for subacute stroke and what are the features?
Time: 1-3 weeks
CT fogging phenomenom
What is the timing for chronic stroke and what are the features?
Time: >3 weeks
Residual swelling passes, negative mass effect
Why is CTA used in stroke?
- Identify thrombus within vessel which may guide thrombolysis or clot retrieval
- Evaluation of carotid and vertebral arteries establishing stroke etiology and assess limitation for endovascular treatment (stenosis, tortuosity)
- Prior to paediatric thrombolysis some guidelines only advise for arterial thrombolysis
What products are used for thrombolysis?
Streptokinase and altreplase (rtPA)
What do thrombolysis products do?
Activate conversion of plasminogen to plasmin an enzyme responsible for breakdown of clot
Which vessels of the brain is mechanical thrombectomy useful in stroke?
Large, anterior circulatory vessels
What is a TICI scale and what does it predict?
Thrombolysis in Cerebral Infarction
Determines response of thrombolytic therapy for ischaemic stroke or post endovascular revascularisation predicting prognosis
In order of occurrence what are the most common brain tumors?
Neuroepithelial, meningioma, metastases, pituitary
Describe appearance and presentation of meningioma
Well defined rounded dural mass with extensive regions of dural thickening. Patients present with headache, paresis and change in mental status
What is vasogenic oedema, its appearance and what is it associated with?
Vasogenic oedema is fluid within the interstitial space with disrupted blood brain barrier. Grey/white matter more pronounced as it affects only white matter. It is associated with brain tumors
What is cytotoxic oedema, its appearance and what is it associated with?
Cystotoxic oedema is fluid within cells from liquefactive necrosis. It involves both grey and white matter so there is less differentiation of grey/white matter. It is associated with infarction
What does FAST stand for?
Facial droop
Arm weakness
Slurred speech
Time 4hrs
What is multinodular goitre?
Multiples thyroid nodules of normal, hyper or hypo function
What is the most common demographic for multinodular goitre?
Females 35-50
What is the role of CT in multinodular goitre and what is the appearance on CT?
Characterising multinodular goitre and enlarged heterogenous thyroid
Patients with multinodular goitre are at risk of what?
Thyrotoxicosis
What is the appearance of metastatic lymph nodes on CT
Round with ill defined margins, cortical hypertrophy, heterogenous enhancement, central necrosis
What is the appearance of non-metastatic lymph nodes on CT?
Smooth and well-defined, homogenous uniform enhancement, no necrosis
What is the appearance of acute sinusitis on CT?
Peripheral mucosal thickening, gas bubbles, obstruction of ostiomeatal complexes
What is the etiology of chronic sinusitis?
Anatomical variants, chronic allergy, chronic infection
Name the 4 types of pneumothorax
Primary spontaneous, secondary spontaneous, iatrogenic, tension
How does a primary spontaneous pneumothorax present and who is most at risk?
Pleuritic chest pain, mild-moderate dyspnea with no underlying lung diseae
Tall/thin people, Marfan syndrome, homocystinuria
How does a secondary spontaneous pneumothorax present and who is most at risk?
No pleuritic chest pain, severe dyspnea
This with cystic lung disease (bullae, emphysema, asthma, ILD, CF) or parenchymal necrosis (lung abscess, necrotic pneumonia, septic emboli, TB)
What can cause an iatrogenic pneumothorax?
Percutaneous biopsy, oesophageal perforation, CVC/NG placement, trauma
What occurs to produce a tension pneumothorax?
Intrapleural air accumulates progressively exerting positive pressure on mediastinal and intrathoracic structures (creates a one way valve)
Define emphysema
Abnormal permanent enlargement of the airspaces distal to the terminal bronchioles accompanied by destruction of the alveolar wall without obvious fibrosis
Panlobar emphysema affects which part of the lungs and what causes it?
Lower zones matching areas of maximal blood flow
A1A deficiency and ritalin lung
Paraseptal emphysema affects which part of the lungs and what causes it?
Peripheral parts adjacent to pleural surfaces
Smoking
Paraseptal emphysema can lead to what?
Subpleural bullae and spontaneous pneumothorax
Centrilobar emphysema affects which part of the lungs and what causes it?
Proximal respiratory bronchioles particularly upper zones
Smoking
Which is the most common form of emphysema?
Centrilobar
How does emphysema present?
Tachypnea, absence of cyanosis, decreased breath sounds, hyperinflation
What does the term lymphadenopathy refer to?
Pathology of lymph nodes including abnormal number, derrangement (cystic/necrotic), enlargement
Define bronchiectasis
Irreversible abnormal dilatation of bronchial tree as a response to inflammation and obstruction/impaired clearance
What are the causes of bronchiectasis?
Idiopathic, impaired host defences (CF, HIV, immunodeficiency), post infective (pneumonia, bronchitis), allergic/autoimmune, obstruction (COPD, malignancy)
What are the CT features of bronchiectasis?
Bronchus visualised within 1cm of pleural surface, lack of tapering, increased bronchoarterial ratio, bronchial wall thickening, air trapping
What are the types of bronchiectasis and which is least common?
Cylindrical, varicose and cystic
Varicose is least common
What are the signs of PE?
Non-specific: dyspnea, chest pain and haemoptysis
What is the primary cause of death associated with PE?
Right ventricular failure due to pressure overload
What are risk factors for PE?
Hypercoaguable states, recent surgery, pregnancy, immobility, malignancy, OCP use, previous DVT
What is a D-Dimer?
A small protein fragment present in the blood after a clot has been degraded by fibrinolysis
What parts of the thyroid does parathyroid hyperplasia affect and what does it cause?
All 4 parathyroid glands
Hypercalcaemia
What is the most common cause of hyperparathyroidism?
Adenoma
How are the spleen and liver commonly injured?
Blunt trauma
What is the best phase to assess the splenic parenchyma?
Portal venous
What are the main splenic injuries and their CT appearances?
Laceration: irregular, non-perfused region
Subcapsular and parenchymal haematoma: Elliptical collection of low attenuation blood
Active haemorrhage: high attenuation blood
What are the main liver injuries and their CT appearances?
Laceration: irregular, non-perfused region
Subcapsular and parenchymal haematoma: Elliptical collection of low attenuation blood
Active haemorrhage: high attenuation blood
Name the 3 benign liver lesions
Adenoma, haemangioma, focal nodular hyperplasia
How do benign liver lesions appear in multiphase CT?
Slight arterial enhancement (type depending on lesion) enhancement during portal venous indicating no washout
How do malignant liver lesions appear in multiphase CT?
Various enhancement on arterial (depending on lesion), hypo enhancement or rapid washout on portal venous phase
What part of a FNH enhances in arterial phase?
Central scar
Describe the features of a haemangioma
Frequently incidental finding, usually located peripherally with hepatic artery supply
What part of a haemangioma enhances in arterial phase?
Periphery
Describe the features of an FNH
Regenerative mass lesion, well circumscribed but poorly encapsulated with a central scar
Describe the features of a hepatic adenoma
Subcapsular and frequently in the right lobe
How does a hepatic adenoma enhance in arterial phase?
Diffusely
Describe the features of a hepatocellular carcinoma
Most common primary liver tumor, strongly associated with cirrhosis receiving blood supply from hepatic artery
How does a hepatocellular carcinoma enhance in arterial phase?
Completely enhances
Describe the features of a cholangiocarcinoma
Mass forming tumor of cholangiocystes with poor prognosis, can be periductal or intraductal
How does a cholangiocarcinoma enhance in arterial phase?
Rim enhancement
Are liver metastases hyper or hypovascular?
Both
What are the most common primaries found in the liver?
GI, breast, lung, melanoma, genitourinary
What is the difference between a simple renal cyst and a complex renal cyst?
Simple: Well defined, thin walled, water attenuation, non-enhancing
Complex: Well defined, thin walled, hyperattenuating (70-90HU)
What is the CT appearance of a renal cyst containing RCC?
Increasing septation, thick wall, calcification, wall enhancement
What are the risk factors of renal stones?
Low fluid intake, urinary tract malformations, UTI, cystinuria, hypercalciuria, (high sodium intake), hyperoxaluria (high oxalate diet)
What are the indications for surgical management of renal stones?
> 5mm, extended duration of symptoms, proximal location, infection/sepsis, professions, failed conservative management
What are the more dense compositions of renal stones?
Oxalate, hydroxylapatite, cystine
What is the least dense composition of renal stones?
Uric acid
What is the typical presentation of appendicitis?
Fever, localised pain, high WCC, N&V
What is the cause of appendicitis?
Obstruction of the appendiceal lumen, resultant build up of fluid, secondary infection, venous congestion, ischaemia and necrosis
What is the appearance of appendicitis on CT?
> 6mm dilated lumen, thickened enhancing wall, thickening of cecal apex, periappendiceal inflammation including adjacent fat stranding, extraluminal fluid, abscess, appendicolith, reactive nodal prominence/enlargement, non-enhancing mucosa representing necrosis
What is the pathogenesis of a psoas abscess?
Haematogenous spread of infectious process
What are the risk factors of a psoas abscess?
DM, IVD, AIDS, renal failure, immunosuppression
What are the 4 categories of causes of small bowel obstruction?
Congenital, extrinsic, intrinsic, intraluminal
What are the causes of congenital SBO?
Jejunal atresia, ileal atresia, volvulus, mesenteric cyst
What are the causes of extrinsic SBO?
Fibrous adhesions, hernia, endometriosis, mass
What are the causes of intrinsic SBO?
Inflammation, tumor, radiation enteritis, intestinal ischaemia, intramural haematoma, intussusception
What are the causes of intraluminal SBO?
Foreign body, gallstone ileus, meconium ileus, migration of gastric balloon
What are the CT findings of SBO?
Dilated small bowel loops >3cm, normal or collapsed loops distally, small bowel faeces sign
What are the symptoms of SBO?
Cramping abdominal pain and distension, N&V
What are the causes of LBO?
Colonic cancer, acute diverticulitis, volvulus, ischaemic stricture, faecal impaction, hernia
What are the CT findings of a LBO?
Distended large bowel, enhancing thin stretched wall, transition point distal to obstruction
Define ileus
Failure of passage of enteric contents through small bowel and colon that are not mechanically obstructed, represents paralysis of intestinal motility
What are the causes of an ileus?
Drugs, metabolic, sepsis, abdominal trauma or surgery, myocardial infarction, head injury, peritonitis, retroperitoneal haematoma
What is a paralytic ileus and why is it concerning?
An ileus that has been prolonged for >72 hours and is concerning for SBO, bowel perforation, peritonitis and intra-abdominal abscess
How is a diagnosis of acute pancreatitis made?
Fulfilling two of the following:
- Acute onset of persistent, severe epigastric pain
- Lipase/amylase >3 times upper limit of normal
- Characteristic imaging features on CT, MRI or U/S
When is imaging of acute pancreatitis required?
When acute appendicitis is suspected but the first two criteria are not met
What are the two types of pancreatitis?
- Interstitial odematous pancreatitis
2. Necrotising pancreatitis
What are the causes of acute pancreatitis?
gallstone passage/impaction, alcohol abuse, metabolic disorder, autoimmune, penetrating peptic ulcer, trauma, malignancy, hereditary, malnutrition, infection (mumps hepatitis, HIV), toxins, drugs, CF, systemic lupus erythematous
What is the presentation of acute pancreatitis?
Acute onset of severe epigastric pain, poorly localised tenderness, exacerbated in supine position, radiates to back, elevation of amylase/lipase
What are the CT findings of acute pancreatitis?
Focal or diffuse parenchymal enlargement, changes in density due to oedema, indistinct pancreatic margins, fat stranding
How is infective necrosis distinguished from liquefactive necrosis?
Presence of gas and FNA
What is the main CT finding of necrotic pancreatitis and what phase is it best appreciated?
Lack of parenchymal enhancement
Late arterial
When is CT best performed in acute pancreatitis and why?
72 hours post initial presentation of symptoms as to not underestimate severity
Define chronic pancreatitis
Continuous prolonged inflammatory and fibrosing process resulting in irreversible morphologic changes and permanent endocrine and exocrine dysfunction
What are the causes of chronic pancreatitis and what is a useful acronym?
TIGAR-O Toxic Idiopathic Genetic Autoimmune Recurrent Obstructive
How does chronic pancreatitis present?
Exacerbations of acute pancreatitis with epigastric pain, jaundice due to obstructive biliary outflow, exocrin dysfunction (malabsorption) endocrine dysfunction (diabetes)
What are the CT findings of chronic pancreatitis?
Dilatation of main pancreatic duct, pancreatic calcification, atrophy, pseudocysts
What is a lipoma?
Benign soft tissue tumor composed of mature adipocytes of low attenuation -65 to 120HU
When do lipomas require further assessment and why?
When they lie ntramuscular, intermuscular or retroperitoneal as they are more likely to be malignant
What patient groups are high risk for ovarian cysts?
Post menopause, family history, BRCA1 or 2 carriers
Name the different types of ovarian cysts
Simple, haemorrhagic, mature cytic teratoma, endometrioma, other
What does a mature cystic teratoma consist of?
Germ cells
When do simple cysts require further evaluation?
> 7cm
What is a haemorrhagic cyst?
Bleeding into follicle or follicular cyst bleeds
What is an indirect inguinal hernia?
Bowel loop protrudes deep inguinal ring, traverses inguinal canal and exits via superficial inguinal ring inside spermatic cord
What is a direct hernia
Bowel loop protrudes through deep inguinal ring, in posterior wall of inguinal canal and exits via the superficial inguinal ring
What ligaments are included in the posterior ligamentous complex?
Supraspinous, interspinous, ligamentum flavum
What are the CT features of an injured PLC?
Widening of interspinous space, avulsions or transverse fractures of spinous processes or articular facets, widening or dislocation of facet joints, vertebral body translation or rotation
What are the CT findings of a compression fracture?
Loss of height of anterior vertebral body
Superior end plate fractures
Posterior cortex of body intact
What are the CT findings of a burst fracture?
Retropulsion of posterosuperior vertebral body fragment
Sagittal fracture of body and posterior elements
Widening of interpedicular distance
What are the CT findings of a translation/rotation fracture?
Displacement in horizontal plane anterior or lateral
Facet joint disruption or dislocation
Oblique array of fragments
PLC always involved
What are the CT findings of a distration fracture?
Displacement in vertical plane
More severe compression than simple wedge fracture
Separation of posterior elements
What is a disc herniation?
Displacement of intervertebral disc material beyond normal confines of disc but involving less than 25% of circumference
What is a disc protrusion?
Base is wider than herniation confined to a single disc level with outer annular fibres intact
What is a disc extrusion?
Base narrower than herniation dome and may extend above/below endplates, It is a complete annular tea with passage of nuclear material beyond disc annulus
When a disc herniation is not contained, what is meant by that?
There is a tear of outer fibres of annulus fibrosus and posterior longitudinal ligament
