The abdominal aorta is the main blood vessel in the abdominal cavity that transmits oxygenated blood from the thoracic cavity to the organs within the abdomen and to the lower limbs.
It is a continuation of descending thoracic aorta at T12 posterior to the median arcuate ligament...
Abdominal aortic aneurysms (AAA) are focal dilatations of the abdominal aorta that are 50% greater than the proximal normal segment or that are >3 cm in maximum diameter.
Its prevalence increases with age. Males are much more commonly affected than females (with a male:female r...
Abdominal aortic aneurysm (AAA) rupture is a feared complication of abdominal aortic aneurysm and is a surgical emergency.
Abdominal aortic aneurysms are common and affect ~7.5% of patients aged over 65 years 6.
The classical triad of pain, hypotension and ...
Abdominal aortic injuries are very rare and are much less common than thoracic aortic injury.
Aortic injury occurs in <1% of blunt trauma patients, with abdominal aortic injury representing only ~5% of all aortic injuries 1. Males are more frequently injured, with the median a...
Abernethy malformations are an extremely rare anomalous group of the splanchnic venous system. They comprise of congenital portosystemic shunt and results from persistence of embryonic vessels.
Type I malformations are thought to only occur in females with type II having a male p...
An aberrant internal carotid artery is a variant of the internal carotid artery (ICA) and represents a collateral pathway resulting from involution of the normal cervical portion (first embryonic segment) of the ICA 5.
There is consequent enlargement of the usually small collaterals which cours...
An aberrant left pulmonary artery (or pulmonary sling) represents an anatomical variant that may result in symptoms because of compression of local structures, in particular, the trachea.
Aberrant left pulmonary arteries are thought to arise from a failure of formation of the 6th aor...
Aberrant right subclavian arteries (ARSA), also known as arteria lusoria, are the commonest of the aortic arch anomalies 2.
The estimated incidence is 0.5-2%.
They are often asymptomatic, but around 10% of people may complain of tracheo-oesophageal symptom...
An absent infrarenal inferior vena cava (IVC) can be congenital due to failure of development of the posterior cardinal and supracardinal veins, or acquired as result of intrauterine or perinatal inferior vena cava thrombosis.
It is an extremely rare anomaly.
The accessory (or superior) hemiazygos vein forms part of the azygos system and along with the hemiazygos vein, it is partially analogous to the right-sided azygos vein. It drains the left superior hemithorax.
Origin and course
The accessory hemiazygos vein is formed by the con...
The accessory middle cerebral artery is a variant of the middle cerebral artery (MCA) that arises from the anterior cerebral artery (ACA). It is different from a duplicated middle cerebral artery, in which the duplicated vessel originates also from the distal end of the internal carotid artery (...
Accessory renal arteries are a common variant and are present in ~25% (range 20-30%) of the population.
Sometimes, the term extrarenal artery may be used 2 with a further subclassification of:
aberrant renal artery: supplying the superior and/or inferior pole of the kidney
accessory renal art...
An accessory right inferior hepatic vein is the most common variation of the hepatic veins. It is present in up to 48% of the population and drains the posterior part of the right lobe (mainly segments 6 and 7) directly into the inferior vena cava.
Variations in hepatic vascular anatomy are pa...
There are many acquired aortic conditions. These include
aortic rupture / transection
ascending aortic aneurysm
thoracic aortic injury
abdominal aortic aneurysm
inflammatory abdominal aortic aneurysm
Acute aortic syndrome (AAS) describes the presentation of patients with one of a number of life threatening aortic pathologies that give rise to aortic symptoms.
The spectrum of these aortic emergencies include:
aortic intramural haematoma
penetrating atherosclerotic ulcer
Acute occlusion of the basilar artery may cause brainstem or thalamic ischaemia or infarction. It is a true neuro-interventional emergency and, if not treated early, brainstem infarction results in rapid deterioration in the level of consciousness and ultimately death.
Acute coronary syndrome (ACS) is a group of cardiac diagnoses along a spectrum of severity due to the interruption of coronary blood flow to the myocardium, which in decreasing severity are:
ST elevation myocardial infarction (STEMI)
non-ST elevation myocardial infarction (non-STEMI)
Acute superior mesenteric artery occlusion, which can then result in an acute mesenteric ischaemia, can be a life threatening event related to the artery supplying the majority of the small bowel and right side of the colon.
An acute occlusion is an uncommon event that typically...
Adrenal haemangiomas are rare benign tumours that are usually incidentally identified (one example of an adrenal incidentaloma). Its significance mainly relates to the difficulty in differentiation from other malignant lesions.
Although these can be found at any age, they are mos...
Adrenal lymphangiomas (also known as cystic adrenal lymphangiomas) are rare, benign vascular adrenal lesions.
According to one series, there may be a slight right-sided and female predilection 3.
It is supposed to occur as a result of a developmental abnormality of lym...
Human alpha fetoprotein (AFP) elevation may occur in a vast number of conditions:
liver tumours (hepatocellular carcinoma, hepatoblastoma)
<10 ng/ml is within normal limits
>20 ng/ml is above normal limits but has low specificity for tumor since it may occur in a setting of diffuse live...
Amniotic fluid emboli (AFE) is a special type of pulmonary embolism where the embolus is comprised of amniotic fluid. It can be a highly fatal complication of pregnancy, with an 80% maternal mortality rate.
It is thought to complicate 1/8000-80,000 pregnancies.
Aneurysms are focal abnormal dilatation of a blood vessel. They typically occur in arteries, venous aneurysms are rare. Aneurysms may also occur in the heart.
false aneurysm (or pseudoaneurysm)
The angiographic string sign, also known as the carotid string sign, refers to the thin string of intravenous contrast material distal to a stenotic focus in the internal carotid artery (ICA).
A thin stripe of flow is caused by decreased pressure and flow distal to the stenosis, whi...
Angiosarcomas (like haemangiopericytomas and haemangioendotheliomas) are tumours that arise from vascular structures. They are typically difficult to distinguish from one another on imaging alone.
Angiosarcomas, are the most aggressive of the three, frequently having metastases at the time of ...
Annulo-aortic ectasia refers to a proximal dilatation of the ascending aorta at the level of the aortic annulus, it is also the same level of sinus of Valsalva.
Annulo-aortic ectasia occurs with connective tissue diseases such as Marfan disease and Ehlers Danlos syndrome. It is a cys...
The anterior cerebral artery along with the middle cerebral artery forms at the termination of the internal carotid artery. It is the smaller of the two, and arches anteromedially to pass anterior to the genu of the corpus callosum, dividing as it does so into its two major branches; pericallosa...
The anterior choroidal artery (AChA) supplies several crucial anatomical structures of the brain important for vision and motor control. Identification of AChA is important because of its strategic and extensive area of supply as well as large variations in the territorial distribution.
The anterior communicating artery (ACOM) arises from the anterior cerebral artery and acts as an anastomosis between the left and right anterior cerebral circulation. It is about 4mm in length and demarcates the junction between the A1 and A2 segments of the anterior cerebral artery.
The anterior inferior cerebellar artery (AICA) is one of three vessels that provides arterial blood supply to the cerebellum. It has a variable origin, course and supply, with up to 40% of specimens not having an identifiable standard AICA. The amount of tissue supplied by the AICA is variable (...
The anterior jugular vein is a paired tributary of the external jugular vein.
Origin and course
The anterior jugular vein has its origin in the region of the hyoid bone or suprahyoid neck, as the confluence of several small superficial veins. It descends near the midline, medial...
The anterior spinal artery supplies the anterior portion of the spinal cord and arises from the vertebral artery in the region of the medulla oblongata. The two arteries (one of which is usually bigger than the other) anastamose in the midline to form a single anterior spinal artery at the level...
The anterior tibial artery is the main arterial supply of the anterior compartment of the leg.
The anterior tibial artery arises from the popliteal artery in the popliteal fossa and continues distally as the dorsalis pedis artery.
The popliteal artery usually divides at...
The anterior tibial veins, continuations of the venae comitantes of the dorsalis pedis artery, leave the anterior compartment between the tibia and fibula and pass through the proximal end of the interosseous membrane. They unite with the posterior tibial veins to form the popliteal vein at the ...
Anti-neutrophil cytoplasmic antibody associated vasculitides refer to a group of heterogeneous autoimmune diseases characterized by necrotising vasculitides and positive anti-neutrophil antibody titres. They are reactive to either proteinase-3 (PR3-ANCA) - cANCA or myeloperoxidase (MPO-ANCA) - p...
Antiphospholipid syndrome (APS) is a systemic autoimmune disorder. It is usually defined as the clinical complex of vascular occlusion and ischaemic events occurring in patients who have circulating antiphospholipid antibodies.
Patients have circulating antiphospholipid antibodies cr...
The aorta, the great artery, is the largest artery of the human body and carries oxygenated blood ejected from the left ventricle to the systemic circulation. It is divided into:
It has branches from each section a...
The broad term aortic aneurysm is usually reserved for pathology discussion. More specific anatomic and radiologic discussion is based on the location of the aneurysm:
thoracic aortic aneurysm
abdominal aortic aneurysm
The aortic annulus is a fibrous ring at the aortic orifice to the front and to the right of the atrioventricular valve and is considered the transition point between the left ventricle and aortic root. It is at the level of the sinus of Valsalva and is the site of aortic valve leaflet insertion....
The aortic arch represents the direct continuation of the ascending aorta and represents a key area for a review of normal variant anatomy and a wide range of pathological processes that range from congenital anomalies to traumatic injury.
origin: continuation of the ascending aorta at...
A mnemonic to remember the major branches of the aortic arch is:
A: arch of aorta
B: brachiocephalic trunk
C: left common carotid artery
S: left subclavian artery
Aortic dissection is one of the acute aortic syndromes and a type of arterial dissection. It occurs when blood enters the medial layer of the aortic wall through a tear or penetrating ulcer in the intima and tracks along the media, forming a second blood-filled channel within the wall.
The aortic hiatus is one the three major apertures through the diaphragm and lies at the level of T12. Strictly speaking, it is not a real aperture in the diaphragm, but an osseoaponeurotic opening between it and the vertebral column.
The hiatus is situated slightly to the left of the midline ...
Aortic intramural haematoma (IMH) is an atypical form of aortic dissection due to haemorrhage into the wall from the vasa vasorum without an intimal tear.
Typically aortic intramural haematomas are seen in older hypertensive patients. The same condition may also develop as a resul...
The aortic isthmus is the part of the aortic arch just distal to the origin of the left subclavian artery at the site of the ductus arteriosus.
This portion of the aorta is partly constricted in the fetus because of the lack of flow within the aortic sac and ascending aorta. It marks the partia...
Aortic pseudoaneurysms typically occur as a result of trauma. They can be acute or chronic.
Aortic pseudoaneurysms are contained ruptures of the aorta in which the majority of the aortic wall has been breached, and luminal blood is held in only by a thin rim of the remaining wall or ...
The aortic root is a part of the thoracic aorta and connects the heart to the systemic circulation.
The aortic root lies between the junction of the aortic valve and ascending aorta. It has several subparts 1:
aortic valve leaflets and leaflet attachments
annulus: fibrous ring...
Aortic spindles are an anatomical variant of the proximal descending thoracic aorta. It occurs just distal to the aortic isthmus, and has a circumferential smooth bulging appearance.
ductus diverticulum: not circumferential
thoracic aortic aneurysm
Aortic valve stenosis (also known as aortic stenosis) is the most common type of valvular heart disease that requires valve replacement. It can be classified according to the anatomical location: supravalvular, valvular and subvalvular 1.
There are several causes of aortic valve ...
Aortitis refers to a general descriptor that involves a broad category of infectious and non-infectious conditions where there is abnormal inflammation (i.e. vasculitis) of the aortic wall.
The presentation is non-specific with fever, pain and weight loss.
Aorto-caval fistula is a rare and devastating complication of abdominal aortic aneurysm (AAA), wherein the aneurysm erodes into the inferior vena cava.
Spontaneous rupture of an AAA into the adjacent vena cava occurs in <1% of all aneurysms and in ~3% of ruptured aortic aneurys...
Aorto-enteric fistulation is an uncommon catastrophic cause of gastrointestinal haemorrhage. Aortic fisultas can be primary (associated with an abdominal aortic aneurysm) or secondary (associated with graft repairs).
The annual incidence of primary aorto-enteric fistulas is thoug...
Aorto-iliac occlusive disease refers to complete occlusion of the aorta distal to the renal arteries.
When the clinical triad of impotence, pelvis and thigh claudication, and absence of the femoral pulses are present, it may also be called Leriche syndrome, which usually affects y...
Aorto-left renal vein fistula is an extremely rare complication of abdominal aortic aneurysm rupture. The initial clinical presentation is often non-specific, however, characteristic imaging findings, if recognised early, can lead to prompt diagnosis and assist in surgical planning.
Aortopulmonary septal defect (APSD), also known as aortopulmonary window (APW), is a congenital anomaly where there is an abnormal communication between the proximal aorta and the main pulmonary artery in the presence of separate aortic and pulmonary valves.
APSD should not be conf...
Aortosternal venous compression refers to compression of the brachiocephalic vein as a result of its position between the sternum and the aorta(or regional arteries). It can occur with normal as well as variant anatomy (aberrant right subclavian artery 1).
It is asymptoma...
The appendicular artery is a branch of the ileal or posterior caecal branch of the ileocolic artery, which is from the superior mesenteric artery.
It courses posteriorly to the terminal ileum in the free wall of the mesoappendix to supply the appendix.
The arc of Barkow is formed by the anastomosis of the right gastroepiploic (a branch of the gastroduodenal artery) and left gastroepiploic (a branch of the splenic artery) arteries.
The arc of Barkow supplies the transverse colon with multiple ascending branches.
The arc of Buhler (AOB) is a persistent embryologic connection between the coeliac artery and superior mesenteric artery. This arch is is independent of both the gastroduodenal and dorsal pancreatic artery.
It travels vertically, ventral to the abdominal aorta. It is present in 1-4% of indivi...
An Arc of Buhler aneurysm is a rare pathology that can occur in an arc of Buhler. It can occur in association with stenoses of celiac axis. This is considered a true aneurysm. Transcatheter embolization has been successfully tried as the management technique.
On imaging ...
The arc of Riolan (AOR), also known as the mesenteric meandering artery (of Moskowitz) or central anastomotic mesenteric artery, is an arterio-arterial anastomosis between the superior and inferior mesenteric arteries.
It is an inconstant artery that connects the proximal superio...
Arterial dissection occurs when blood enters the media through a tear or ulcer in the intima and tracks along the media, forming a second blood-filled channel within the wall. The normal lumen lined by intima is called the true lumen and the blood-filled channel in the media is called the false ...
In patients with a left ventricular assist device (LVAD), spectral Doppler waveforms are altered due to continuous flow provided by the pump in the device:
waveforms are monophasic with a constant antegrade flow and no flow below the baseline.
the waveform is typically parvus-tardus with a slo...
The arteries of the head and neck are branches of the common carotid and and subclavian arteries.
(1st part) mandibular
The arterial supply of the lower limbs is via vessels arising from the external iliac artery.
The common femoral artery (CFA) is the direct continuation of the external iliac artery. It begins at the level of the inguinal ligament. It terminates as it gives off the profunda femoris and continu...
The arterial supply of the upper limb is derived via the subclavian artery which receives blood from the brachiocephalic artery which is the first of the branches from the aortic arch.
The subclavian artery gives off several branches for the head, neck and chest as well as scapular branches bef...
Arterial supply to the foot can be divided into plantar and dorsal components.
Plantar arterial supply
Medial plantar artery
branch off the posterior tibial artery
smaller calibre vessel
supplies the medial side of the foot, abductor hallucis and flexor digitorum brevis.
provides the arter...
The arterial supply to the hand can be divided into palmar and dorsal components.
Palmar arterial supply
The palmar arterial supply can be divided into superficial and deep components.
Superficial palmar arch
superficial branch of the ulnar artery
distal to flexor ret...
Arteriosclerosis is defined by thickening and loss of elasticity of the arterial walls.
There are three patterns (arteriosclerosis is used as a generic term for all patterns above):
atherosclerosis: large and medium-sized arteries
Monckeberg medial calcific sclerosis: muscular arteries
Arteriovenous access is required for haemodialysis in renal failure patients. The upper limb is generally preferred as a site, however, lower limb access can also be obtained. Ultrasound is the preferred modality for evaluation of the vessels prior to creating an access.
An arteriovenous fistula (AVF) is an abnormal connection between an adjacent artery and vein. Unlike an arteriovenous malformation (AVM), these are frequently acquired lesions, rather than developmental abnormalities.
AVFs have a number of etiologies. They can be iatrogenic in origin...
Arteriovenous malformations (AVMs) are characterised by an abnormal leash of vessels allowing for arteriovenous shunting. They can occur anywhere in the body but have a predilection towards the head and neck. There is a direct arteriovenous communication with no intervening capillary bed. They ...
The artery of Adamkiewicz, also known as the great anterior radiculomedullary artery or arteria radicularis anterior magna, is the name given to the dominant thoracolumbar segmental artery that supplies the spinal cord.
The artery of Adamkiewicz has a variable origin but ...
The artery of Percheron is a rare variant of the posterior cerebral circulation characterised by a solitary arterial trunk that supplies blood to the paramedian thalami and the rostral midbrain bilaterally.
The term is used to refer to a solitary arterial trunk that branches from...
Artery of Percheron territory infarct is rare, on account of the relative rarity of the artery of Percheron, and presents with a variety of signs and symptoms collectively termed the paramedian thalamic syndrome. It is a type of posterior circulation infarction.
On imaging, it is classically ch...
The artery to the ductus deferens (deferential artery) is a branch of the superior vesicle artery, which in turns arises from the internal iliac artery via the umbilical artery.
origin: superior vesical artery
main branch: no named branches
course: accompanies the ductus defere...
The ascending aorta is the first part of the aorta, and begins at the aortic valve - located obliquely just to the left of the midline at the level of the the third intercostal space. It terminates as it exits the fibrous pericarium where it becomes the aortic arch, in the plane of Ludwig, a hor...
Dilatation of the ascending aorta is a common finding in the elderly but unusual in younger patients.
Causes include 1:
senile / atherosclerotic ectasia / hypertension
aneurysm of the ascending aorta
aortic dissection (Stanford type A / DeBakey type I and II)
Ascending aortic aneurysms are the most common subtype of thoracic aortic aneurysms, and may be true or false injuries. Aneurysmal dilatation is considered when the ascending aorta measures >4.0 cm in diameter.
Ascending aortic aneurysms represent 60% of thoracic aortic aneury...
The ascending lumbar communicant vein is a communication between the left ascending lumbar vein and the left renal vein. Because of its retroperitoneal location, when dilated, it may be mistaken for a lymph node on non-contrast studies with thick collimation.
The image shows the left renal vein...
The ascending pharyngeal artery, the smallest branch of the external carotid, is a long, slender vessel, deeply seated in the neck, beneath the other branches of the external carotid and under the stylopharyngeus.
origin: a branch of the external carotid artery
course: vertically with...
The axillary artery represents the continuation of the subclavian artery and is a major artery of the upper limb.
origin: continuation of the subclavian artery as it passes under the midpoint of the clavicle on the outer edge of the first rib
termination: continues as the brachial ar...
A useful mnemonic to remember the branches of the axillary artery is:
S AL SAP
S: Superior thoracic artery (from 1st part)
A: Acromiothoracic artery (from 2nd part)
L: Lateral thoracic artery (from 2nd part)
S: Subscapular artery (from 3rd part)
A: Anterior circumflex humeral art...
An azygos anterior cerebral artery is uncommon to rare variant of the circle of Willis where the two A1 segments of the anterior cerebral artery (ACA) join to form a single trunk. As a result, there is no anterior communicating artery. This organisation is similar to that seen in lower primates ...
An azygos arch valve refers to a venous valve at the site of the azygos arch. They are considered common and are more frequently seen at CT when high contrast material injection rates and right arm injections are used 2. They can be of various sizes and shapes, and many of them show features of ...
Azygos continuation of the inferior vena cava (also known as absence of the hepatic segment of the IVC with azygos continuation) is an uncommon vascular anomaly and is a cause of a dilated azygos vein.
Azygous continuation of the IVC has a prevalence ~1.5% (range 0.2-3%) 1.
The azygos vein is a unilateral vessel that ascends in the thorax to the right side of the vertebral column, carrying deoxygenated blood from the posterior chest and abdominal walls. It forms part of the azygos venous system.
The azygos vein is formed by the union of the...
The azygos (venous) system is a collective term given to the H-shaped configuration of the azygos, hemiazygos, accessory hemiazygos veins and left superior intercostal vein.
It is responsible for draining the thoracic wall and upper lumbar region via the lumbar veins and posterior intercostal v...
Barrow caroticocavernous fistula classification divides caroticocavernous fistulas into direct (type A) or indirect (types B-D). This classification was proposed by Barrow et al. in 1985 1 and at the time of writing (mid 2016) remains the most widely used system for describing caroticocavernous ...
Basal ganglia haemorrhage is a common form of intracerebral haemorrhage, and usually as a result of poorly controlled long standing hypertension. The stigmata of chronic hypertensive encephalopathy are often present (see cerebral microhaemorrhages).
Other sites of hypertensive haemorrhages are ...
The basal veins, also known as the veins of Rosenthal, are paired, paramedian veins which originate on the medial surface of the temporal lobe and run posteriorly and medially. It passes lateral to the midbrain through the ambient cistern to drain into the vein of Galen with the internal cerebra...
The basilar artery is part of the posterior cerebral circulation. It artery arises from the confluence of the left and right vertebral arteries at the base of the pons as they rise towards the base of the brain.
origin: vertebral artery confluence
course: ventral to pons in the pontin...
Basilar artery fenestration (or more simply, basilar fenestration) is the most common intracranial arterial fenestration. It refers to duplication of a portion of the artery. Its reported is highly variable depending on the technique used:
~0.5% (0.3-0.6%) at angiography (presumably low due to ...