Single umbilical artery (SUA) results when there is a congenital absence of either the right or left umbilical artery. In the usual situation, there are paired umbilical arteries. For unknown reasons, the absence of the left umbilical artery is much more common (~70%).
The sinotubular junction is the region of the ascending aorta between the aortic sinuses (of Valsalva) and where the normal tubular configuration of the aorta is attained.
Sinus of Valsalva aneurysms are a cause of thoracic aortic dilatation. They can be either congenital or acquired (mycotic).
There is a male predilection (M:F ratio being around 3-4:1). They are relatively more common in eastern and Asian populations and can occur in any age group ...
Situs classification can be a daunting topic, but it falls into three main groups :
situs solitus: the normal configuration of thoracic and abdominal organs
situs inversus: mirror image of normal
situs ambiguus: an intermediate configuration with duplication (isomerism)
Situs is best thought...
Situs inversus, short form of the Latin “situs inversus viscerum”, is a term used to describe the inverted position of chest and abdominal organs. It is called situs inversus totalis when there is a total transposition of abdominal and thoracic viscera (mirror image of internal organs normal pos...
Situs solitus refers to the normal position of the thoracic and abdominal organs.
On plain radiograph, careful attention should be directed at the location of the aortic arch, gastric fundus, cardiac apex, pulmonary fissures and the branching pattern of ...
The small cardiac vein is a vein of the heart which accompanies the acute marginal artery from the RCA. It courses in the right posterior atrioventricular groove and drains into the coronary sinus close to it’s termination but may drain directly into the right atrium. It drains the right ventric...
The small saphenous vein (SSV) forms part of the superficial venous drainage of the lower limb.
Small saphenous vein is the preferred terminology over other terms such as short saphenous vein, external saphenous vein or lesser saphenous vein 5.
Origin and course
Soft-tissue sarcomas are a heterogeneous group of malignant tumours of mesenchymal origin (sarcoma) that originate from the soft tissues rather than bone. They are classified on the basis of tissue seen on histology. The commoner sarcomas in the adult and paediatric population are listed below.
Sonographic halo sign is used in a number of situations. They include:
hypoechoic halo sign (also known as target or bull's eye sign) in liver metastases: used in hepatobiliary imaging, is a concerning feature for malignant lesion if the lesion is a hyperechoic liver lesion 1,2
The Spetzler-Martin arteriovenous malformation (AVM) grading system allocates points for various features of intracranial arteriovenous malformations to give a grade between 1 and 5. Grade 6 is used to describe inoperable lesions. The score correlates with operative outcome.
size of ni...
The sphenopalatine artery, formerly known as the nasopalatine artery, is the terminal branch of the maxillary artery that is the main supply to the nasal cavity. It is colloquially know as the artery of epistaxis given its common involvement in cases of nose bleeds. It is a major contributor to ...
The sphenoparietal sinus is one of the dural venous sinuses and is located along the posteroinferior ridge of the lesser wing of the sphenoid bone. It consists of the sinus of the lesser sphenoid wing and of the parietal portion of the frontal ramus of the middle meningeal vein. It drains into t...
Spinal arteriovenous malformations (AVMs) are characterised by arteriovenous shunting with a true nidus. They represent ~25% of spinal vascular malformations.
Different types of spinal AVM (see below) have differing age of presentation, but overall 80% present between the age 20 ...
Spinal arteriovenous malformations can be classified in a number of ways:
extramedullary: 80% 1
Or into four types 2:
type I: single coiled vessel (dural AV fistula)
type II: intramedullary glomus AVM
type III: juvenile
type IV: intradural perimedullary (AV fistula)
The spinal cord blood supply is formed by many different vessels with an extensive collateral supply and drainage.
The spinal cord is supplied by three longitudinal arteries:
single anterior spinal artery: supplies the anterior two-thirds of the spinal cord
sizable and formed...
Spinal dural arteriovenous fistulas (SDAVF) are the most common type of spinal vascular malformation, accounting for ~70% of all such lesions.
This article specifically relates to spinal dural arteriovenous fistulas. For a discussion of intracranial dural arteriovenous fistulas refer to the mai...
Spinal vascular malformations (SVM) are rare but knowledge of them is important as if undiagnosed and untreated they can lead to serious complications.
There are two main types of SVMs 1,2:
spinal arteriovenous fistula (AVF): 70% of SVMs
pial: small, large, or giant
dural AVF (DA...
Splenial artery or posterior pericallosal artery arises most commonly from the parieto-occipital branch of the PCA. It represents an important collateral supply from the posterior to anterior cerebral arteries as it anastomoses with the pericallosal artery.
the splenial artery ...
The splenic artery is one of three branches coeliac trunk and supplies the spleen as well as large parts of the stomach and pancreas.
Origin and course
The splenic artery is one of the terminal branches of the coeliac trunk, passing from the coeliac axis toward the splenic hilum...
Splenic artery aneuryms are the commonest visceral arterial aneurysm formation as well as the 3rd commonest abdominal aneurysm (after the aorta and iliac vessels). Aneurysms are usually saccular in configuration and they can either be in the form of a true aneurysm (much more common) or as a pse...
Splenic artery pseudoaneurysms are a rare type of pseudoaneurysm arising from any portion of the splenic artery and its branches.
Unlike splenic artery true aneurysms, splenic artery pseudoaneurysms will nearly always present with symptoms 2. Fewer than 200 cases of sple...
Splenic steal syndrome is a possible complication after liver transplantation. In this syndrome, blood flows preferentially from the celiac artery into the splenic artery and the hepatic artery is relatively hypoperfused as a result. This complication can threaten a liver transplant's survival.
The splenic vein drains the spleen, part of the pancreas, and part of the stomach.
Origin and course
The splenic vein is formed by splenic tributaries emerging at the splenic hilum in the splenorenal ligament at the tip of the tail of pancreas. It runs in the splenorenal ligame...
Spontaneous retroperitoneal haemorrhage (SRH) is a distinctive clinical pathology of retroperitoneal bleeding without a preceding history of trauma.
Clinical presentation may be vague and varied:
no inciting history
no evidence of cutaneous bruising
back, lower abdomin...
The stag's antler sign refers to upper lobe pulmonary venous diversion (cephalisation) in pulmonary venous hypertension or pulmonary oedema as seen on frontal chest radiograph.
The prominence of upper lobe pulmonary veins resemble a stag's antlers. It is the earliest sign of pulmonary venous hy...
Along with the DeBakey classification, the Stanford classification is used to separate aortic dissections into those that need surgical repair, and those that usually require only medical management. The Stanford classification divides dissections by the most proximal involvement:
type A: A aff...
Stewart-Treves syndrome refers to an angiosarcoma seen in the setting of lymphoedema 1.
It was classically attributed to lymphoedemas induced by radical mastectomy to treat breast cancer. Nowadays, we know that it can arise in any chronically lymphoedematous region due to any cause2.
The straight sinus is one of the main dural venous sinuses and is found at the junction between the falx cerebri and the tentorium cerebelli and is triangular in cross section.
It receives the inferior sagittal sinus, the vein of Galen at its anterior end and some superior cerebellar veins alo...
The string of beads sign is the description typically given to the appearance of the renal artery in fibromuscular dysplasia (FMD) but may also be used to describe the appearance of splanchnic arteries in segmental arterial mediolysis (SAM). It refers to the appearance arising from the stenoses ...
String of pearls sign can refer to:
string of pearls sign on an abdominal radiograph of fluid-filled dilated small bowel loops
string of pearls sign on ultrasound in polycystic ovarian syndrome
string of pearls sign for angiographic appearances in fibromuscular dysplasia
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...
The string sign may refer to:
angiographic string sign
gastrointestinal string sign
string sign of parosteal osteosarcoma
Stroke is a clinical diagnosis that refers to a sudden onset focal neurological deficit of presumed vascular origin.
It is divided into two broad categories:
ischaemic stroke (80% 2)
haemorrhagic stroke (15%)
Haemorrhage may be due to hypertension or other secondary causes such as vascular ...
Subarachnoid haemorrhage (SAH) is one of the types of extra-axial intracranial haemorrhage and denotes the presence of blood within the subarachnoid space.
Patients tend to be older middle age, typically less than 60 years old 2. Subarachnoid haemorrhage accounts for 3% of stroke ...
The subclavian arteries are asymmetric paired arteries that supply blood to the posterior cerebral circulation, cerebellum, posterior neck, upper limbs and the superior and anterior chest wall.
Right and left subclavian arteries classically have different origins:
Helpful mnemonics to remember the branches of the subclavian artery include:
Very Indignant Tired Individuals Sip Strong Coffee Served Double Daily
VIT C, D (as in vitamins C and D).
Very Indignant Tired Individuals Sip Strong Coffee Served Double Daily
V: vertebral artery
Subclavian artery stenosis (SAS) refers to narrowing of one or both of the subclavian arteries.
The estimated in the general population as a whole is thought to be around 2-4%, while in those with peripheral vascular disease, it can be as high as 18% 1,4.
It can arise ...
Subclavian steal syndrome (SSS) and subclavian steal phenomenon both result from occlusion or severe stenosis of the proximal subclavian artery resulting in retrograde flow in the ipsilateral vertebral artery.
Subclavian steal phenomenon refers to steno-occlusive disease of the pro...
The subclavian vein (SCV) is the major venous channel that drains the upper limb.
Origin and course
The subclavian vein starts at the crossing of the lateral border of the 1st rib. It then arches cephalad, posterior to the medial clavicle before curving caudally and receiving it...
Subclavian vein stenosis refers to a narrowing of the subclavian vein.
Presentation can be variable ranging from being asymptomatic to having arm swelling, arm pain, paresthaesia, neck pain and occipital headaches.
Subclavian vein stenosis can arise from numbe...
The subcostal arteries are bilateral small arteries that arise of the distal descending aorta which courses laterally beneath the 12th rib. They are the last
The subcostal arteries are analogous to the posterior intercostal arteries, instead in the subcostal space rather than an...
The subscapular artery is the largest branch of the axillary artery.
The subscapular artery originates from the medial surface of the third part of the axillary artery. It passes along the inferior border of the subscapularis muscle and it divides into two branches 1,2:
The Sudeck point (or Sudeck critical point) refers to a specific location in the arterial supply of the rectosigmoid junction, namely the origin of the last sigmoid arterial branch from the inferior mesenteric artery (IMA) 1.
This arterial branch usually forms an anstomosis with a branch of th...
Sulcal arteries are penetrating branches from the anterior spinal artery and extend posteriorly through the anterior median fissure of the spinal cord. The sulcal arteries supply the anterior two-thirds of the spinal cord at any cross-sectional level.
Successive sulcal arteries generally altern...
Sulcal artery syndrome is a rare cause of spinal cord infarction involving the territory of one of the sulcal arteries, which are penetrating branches of the anterior spinal artery, each vessel supplying either left or right side of the cord, but not both. The result is an incomplete Brown-Séqua...
The superficial femoral artery is a continuation of the common femoral artery at the point where the profunda femoris branches. It is the main artery of the lower limb and is, therefore, critical in the supply of oxygenated blood to the leg.
origin: continuation of the common femoral a...
The superficial middle cerebral vein (SMCV) (also known as the Sylvian vein) is one of the superficial cerebral veins. It usually passes along the Sylvian fissure posteroanteriorly, it collects numerous small tubutaries which drain the opercular areas around the lateral sulcus. It curves anterio...
The superficial palmar branch of the radial artery (also known as the palmar cutaneous branch) is a small branch of the radial artery in the distal forearm. It arises from the radial artery just proximal to the flexor retinaculum, which it passes superficially over before entering the hand to su...
The superficial temporal artery is one of two terminal branches of the external carotid artery. It arises in the parotid gland and runs between the deep and superficial lobes, over the zygomatic process before terminating in three branches - parietal, frontal and transverse facial - to supply pa...
The superficial temporal vein arises in a plexus on the side and vertex of the skull and, in the substance of the parotid gland, joins with the maxillary vein to form the retromandibular vein.
The superficial temporal vein originates from a venous plexus on the side and vertex of...
Superficial thrombophlebitis, also called superficial venous thrombosis (SVT), is a pathological condition characterized by the presence of a thrombus in the lumen of a superficial vein, accompanied by inflammatory reaction of adjacent tissues.
Some authors however reserve the term...
Superficial veins of the brain predominantly drain the cerebral cortex, and include:
superior cerebral veins (or superficial cerebral veins)
inferior cerebral veins
superficial middle cerebral veins
superior anastomotic vein (of Trolard)
inferior anastomotic vein (of Labbe)
Some also inclu...
The superior adrenal (suprarenal) arteries area a group of one of the three adrenal arteries that supply the adrenal gland. There are usually numerous small arteries arising from the inferior phrenic artery.
The superior suprarenal arteries arise from the inferior phrenic...
The superior anastomotic vein (or vein of Trolard) connects the superior sagittal sinus and the superficial middle cerebral vein (of Sylvius).
Its size is dictated by the relative size of the superficial middle cerebral vein and the anastomotic vein of Labbé. The vein of Trolard is smaller than...
The superior cerebellar artery (SCA) arises from the distal basilar artery, just below the posterior cerebral artery (PCA) and typically supplies:
whole superior surface of the cerebellar hemispheres down to the great horizontal fissure
most of the cerebellar ...
Superior cerebellar artery infarcts affect the superior cerebellar hemispheres, cerebellar vermis and parts of the midbrain. The superior cerebellar artery is the most constantly identified vessel arising from the basilar artery with its origin just below the posterior cerebral artery in the dis...
The superior cerebral veins drain the superior portion of the cerebral cortex. They run up and medially before draining into the superior sagittal sinus. In a proportion of patients, a large such vein connects the superficial middle cerebral vein to the sinus, and is known as the superior anasto...
The superior epigastric artery is one of two terminal branches of the internal thoracic artery with the other being the musculophrenic artery.
Origin and course
The superior epigastric artery originates at the level of the sixth or seventh costal cartilage. It descends to the a...
The superior gluteal artery is the largest branch of the internal iliac artery and supplies structures within the pelvis and gluteal region.
origin: from the posterior division of the internal iliac artery
location: originates from pelvis and enters the gluteal region
The superior hypophyseal artery (or arteries) is a branch from the C6 segment of the internal carotid artery. It is usually a single trunk which then divides into many small branches, which go on to supply:
pituitary gland (anterior gland)
It is ofte...
The superior laryngeal artery accompanies the internal laryngeal branch of the superior laryngeal nerve, beneath the thyrohyoid muscle.
It pierces the thyrohyoid membrane, and supplies the muscles, mucous membrane, and glands of the larynx, anastomosing with the branch from the opposite side.
Superior mediastinum is an artificially divided wedge-shaped compartment of the mediastinum located between the thoracic plane inferiorly and the thoracic inlet superiorly. The inferior mediastinum, comprising of the anterior, middle and posterior parts, lies inferiorly.
Superior mesentertic arterial (SMA) dissection is an uncommon type of arterial dissection. It can either on its own (rarer) or occur as part of an extension of an aortic dissection.
A spontaneous dissection of the superior mesenteric artery (SMA) is considered the most frequently reported type...
The superior mesenteric artery (SMA) is one of the three non-paired major visceral arteries in the abdominal cavity arising from the abdominal aorta and supplying the midgut.
Single vessel arising anteriorly from the abdominal aorta at the level of L1, usually just below ...
There are two distinct vascular compression disorders due to compression of another structure by the superior mesenteric artery. The terminology is sometimes confusing and they can occur in association.
superior mesenteric artery syndrome (Wilkie syndrome): compression of the third part of th...
Superior mesenteric artery (SMA) syndrome, also known as Wilkie syndrome, is a rare acquired vascular compression disorder in which acute angulation of superior mesenteric artery (SMA) results in compression of the third part of the duodenum leading to obstruction.
It should not be confused wit...
The superior mesenteric vein (SMV) accompanies the superior mesenteric artery (SMA) and drains the midgut to the portal venous system.
Origin and course
Mesenteric venous arcades, which accompany the arteries, unite to form the jejunal and ileal veins in the small bowel mesenter...
The superior ophthalmic vein is a prominent vein of the orbit that is seen on CT and may be enlarged or tortuous in various disease entities.
The vein forms at the confluence of several veins within the superior orbit above the medial palpebral ligament: the angular, supratrochle...
The superior pancreaticoduodenal artery is a branch of gastroduodenal artery that supplies the duodenum and pancreas.
Superior pancreaticoduodenal artery arises after branching off from gastroduodenal artery. It divides into anterior and posterior divisions which supply the pylor...
The superior petrosal sinus is one of the dural venous sinuses and drains the cavernous sinus, posterolaterally to the transverse sinus. It runs along superior aspect of the petrous temporal bone. It receives:
inferior cerebral veins
labyrinthine vein: draining the inner ear ...
The superior phrenic arteries are small branches arising either side from the lower part of the thoracic aorta just before it passes through the aortic hiatus. They anastamose with the pericardiophrenic and musculophrenic arteries to supply the superior surface of the diaphragm.
The superior rectal artery is an artery that supplies bloods to the rectum down to the level of the levator ani 2.
origin: the terminal branch of the inferior mesenteric artery is the superior rectal artery
course: descends into the pelvic cavity in the sigmoid mesocolon, crossing the...
The superior sagittal sinus is the largest dural venous sinus. As the name suggests, it runs in a sagittal plane from the anterior aspect of the falx cerebri to its termination at the confluence of sinuses at the occipital protuberance, where it usually proceeds rightward and into the right tran...
Superior sagittal sinus thrombosis (SSST) is the most common type of dural venous sinus thrombosis and is potentially devastating.
This article focuses on the specific features related to the superior sagittal sinus thrombosis, please refer to the dural venous sinus thrombosis article for a gen...
The superior thoracic aperture, also known as the thoracic inlet or outlet, connects the root of the neck with the thorax.
The superior thoracic aperture is kidney-shaped and lies in an oblique transverse plane, tilted anteroinferiorly to posterosuperiorly.
The superior thoracic artery is the only branch of the first part of the axillary artery. It is only a small and highly variable artery.
Origin and course
The superior thoracic artery originates from the first part of the axillary artery, just inferior to subclavius. It courses...
The superior thyroid artery is a branch of the external carotid artery and supplies the larynx and thyroid gland.
origin: branch of the external carotid artery at the level of the hyoid bone
superior laryngeal artery
The superior ulnar collateral artery is a vessel arising from the brachial artery at the middle part of the arm.
origin: branch of the brachial artery at the middle part of the arm
location: medial lower arm
supply: elbow joint
main branches: posterior ulnar recurrent artery (anasta...
The superior vena cava (SVC) is a large valveless venous channel formed by the union of the brachiocephalic veins. It receives blood from the upper half of the body (except the heart) and returns it to the right atrium.
The SVC begins behind the lower border of the first right co...
Superior vena caval (SVC) duplication is the most common form of a left-sided SVC, where the normal right-sided SVC remains. The right SVC, however, can be smaller in approximately two-thirds of such cases 3.
Results from failure of the embryonic left anterior cardiac vein to regress...
Superior vena cava (SVC) obstruction can occur from extrinsic compression, intrinsic stenosis or thrombosis. Malignancies are the main cause and are considered an oncologic emergency. Superior vena cava syndrome (SVCS) refers to the clinical syndrome with symptoms that results from this obstruct...
SVC obstruction can cause SVC syndrome which is the most common condition affecting this vessel. It can be secondary to an extrinsic compression or intraluminal thrombosis/stenosis. Collateral pathways, with the azygos vein being the most important collateral vessel, form in response to severe n...
The superior vesical artery is a branch of the anterior division of the internal iliac artery. It supplies part of the bladder, ureter, seminal vesicle and ductus deferens.
origin: anterior division of internal iliac artery
supply: superior bladder, ureter, ductus de...
The supraorbital artery is a branch of the ophthalmic artery supplying part of the orbit and face.
The supraorbital artery originates from the ophthalmic artery, upon branching it lies medial to the optic nerve.
The supraorbital artery courses superiorly and med...
The suprascapular artery is 1 of the 4 branches of the thyrocervical trunk (off the first part of the subclavian artery).
It traverses inferiorly and laterally in the lower anterior neck superficial to the anterior scalene muscle and phrenic nerve before crossing the third part of the subclavia...
The supratrochlear artery, also known as the frontal artery, originates from the ophthalmic artery as one of its terminal branches.
After arising from the ophthalmic artery, it pierces the orbital septum and courses in the superior and medial aspect of the orbit, medial to the su...
The supreme intercostal arteries, or superior intercostal arteries, are formed as a direct result of the embryological development of the intersegmental arteries. These arteries are paired structures of the upper thorax which normally form to provide blood flow to the first and second intercosta...
The staging system for moyamoya disease first described by Suzuki and Takaku in their seminal 1969 article1 is still in use today. Formally, the staging refers to findings on conventional angiography, although there are efforts to apply similar systems to MR angiography.2
Suzuki stage appears t...
von Hippel-Lindau disease
Syphilitic aortitis is a form of aortitis which occurs due to syphilis. It usually occurs in tertiary syphilis often 10-30 years after initial infection.
progression into a luetic aneurysm
aortic valvular insufficiency
coronary ostial involvement with coronary ostial stenosis
Systemic hypertension is defined medically as a blood pressure greater than 140/90 mmHg.
essential hypertension: idiopathic (95%)
secondary hypertension: underlying cause identified (5%)
Causes of secondary hypertension:
chronic renal failure...
Systemic lupus erythematosus (SLE) is a complex autoimmune disease with multisystem involvement. It is also sometimes classified as a vasculitis.
There is an overall increased female predilection. In adults, women are affected 9-13 times more than males. In children, this ratio i...