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 ...
Abdominal aortic aneurysms (AAA) are focal dilatations of the abdominal aorta that are 50% greater than the proximal normal segment or >3 cm in maximum diameter.
prevalence of rupture increases with age
males more commonly affected than females
prevalence is almost 1...
Abdominal aortic aneurysm (AAA) rupture is a feared complication of abdominal aortic aneurysm and is a surgical emergency. It is part of the acute aortic syndrome spectrum.
Abdominal aortic aneurysms are common and affect ~7.5% of patients aged over 65 years 6.
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 rare vascular anomalies of the splanchnic venous system. They comprise of congenital portosystemic shunts and result from persistence of the embryonic vessels.
Type I malformations are thought only to occur in females with type II having a male predile...
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 course t...
Aberrant left pulmonary artery, also known as pulmonary sling, represents an anatomical variant characterised by the left pulmonary artery arising from the right pulmonary artery and passing above the right main bronchus and in between the trachea and oesophagus to reach the left lung. It may le...
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 appendicular artery (or artery of Seshachalam) or is a branch of the posterior caecal artery, which in turn arises from the ileocolic artery, and runs in the mesoappendix.
The exact prevalence of this accessory artery and its impact upon the risk of appendicitis varies among studi...
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...
Acute superior mesenteric vein thrombosis is one of the less common causes of intestinal ischaemia.
For a general discussion refer to intestinal ischaemia.
Compared to acute superior mesenteric artery occlusion or ischaemia secondary to small bowel obstruction, acute superior m...
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.
They usually remain asymptomatic throughout life and are almo...
Adrenal vein sampling (AVS) is a procedure used to confirm autonomous hormone production, if it is unilateral or bilateral, to guide further treatment.
AVS is commonly performed in primary aldosteronism, being indicated to identify aldosterone-secreting adenomas and to differentiate...
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.
The anatomy curriculum is one of our curriculum articles and aims to be a collection of articles that represent the core anatomy knowledge.
Head and neck anatomy
Abdominal and pelvic anatomy
Lower limb anatomy
Upper limb anato...
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...
Anomalous course of a coronary artery is a type of congenital coronary artery anomaly. It may represent a benign and incidental finding, but can also be a malignant course predisposing patients to life-threatening myocardial ischaemia or arrhythmias, depending on where the artery runs.
Anomalous left coronary artery from the pulmonary artery (ALCAPA), also known as Bland-White-Garland syndrome (BWG), is a rare congenital coronary artery anomaly and is considered one of the most serious of such anomalies.
There are two forms based on onset of disease each of which has differen...
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...
Anterior cerebral artery (ACA) territory infarcts are much less common than either middle or posterior cerebral artery territory infarcts.
ACA territory infarcts are rare, comprising ~2% of ischaemic strokes 1,2.
ACA stroke syndrome presents as 1,2,3:
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.
Anterior choroidal artery syndrome is a rare entity characterised by the triad of hemiplegia, hemianaesthesia and contralateral hemianopia as a result of cerebral infarction in the anterior choroidal artery territory.
The syndrome may also be associated with neuropsychological disorders, includ...
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 humeral circumflex artery is a vessel arising from the axillary artery at the proximal part of the arm. It is smaller in size relative to the posterior humeral circumflex artery.
origin: branch of the axillary artery at the proximal part of the arm
location: proximal arm...
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 (...
Anterior inferior cerebellar artery (AICA) territory infarcts are much less common than posterior inferior cerebellar artery (PICA) infarcts.
AICA territory infarcts are rare, comprising ~1% of ischaemic cerebellar strokes 2.
AICA stroke syndrome presents ...
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 lateral malleolar artery is the counterpart to the anterior medial malleolar artery, supplies the lateral aspect of the ankle.
Origin and course
branch of anterior tibial artery
runs posterior to the tendons of extensor digitorum longus and fibularis tertius to th...
Anterior medial malleolar artery is the counterpart to the anterior lateral malleolar artery, and supplies the medial aspect of the ankle.
Origin and course
branch of anterior tibial artery
arises approximately 5 cm proximal to the ankle
passes posterior to the tendons of extensor hallucis l...
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 temporal artery is usually a branch of the M1 segment of the middle cerebral artery (MCA) that curves out of the Sylvian fissure and runs over the temporal lobe to supply the anterior third of the superior, middle and inferior temporal gyri.
The temporopolar arter...
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 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 cross-re...
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 aortic valve and is considered the transition point between the left ventricle and aortic root. The annulus is part of the fibrous skeleton of the heart. It is at the level of the si...
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. It is part of the acute aortic syndrome spectrum.
Typically aortic intramural haematomas are seen in older hypertensive patien...
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 the first part of the 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:
three aortic valve leaflets and leaflet attachments
three aortic sin...
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 pulmonary trunk in the presence of separate aortic and pulmonary valves.
APSD should not be confused w...
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 from the subclavian artery. The right subclavian artery originates from the brachiocephalic artery, which is the first branch of the aortic arch. The left subclavian artery originates directly from the aortic arch, being the third branch.
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 is comprised of a complex vascular network formed from the branches and distal continuations of the radial and ulnar arteries. This rich vascular network can be divided into palmar and dorsal components.
Palmar arterial supply
The palmar arterial supply can be d...
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 pericardium where it becomes the aortic arch, in the plane of Ludwig, a ho...
Dilatation of the ascending aorta is a common finding in the elderly but unusual in younger patients.
In adults, an ascending aortic diameter greater than 4 cm is considered to indicate dilatation 4. Aneurysmal dilatation is considered when the ascending aortic diameter reaches or ex...
Ascending aortic aneurysms are the most common subtype of thoracic aortic aneurysms, and may be true or false injuries.
Ascending aortic aneurysms represent 60% of thoracic aortic aneurysms.
Typically ascending aortic aneurysms are an incidental finding a...