The inferior mediastinum is the box-shaped space in the mediastinum below the transthoracic plane of Ludwig between the wedge-shaped superior mediastinum above and the diaphragm and inferior thoracic aperture below. There are no physical structures that divide the superior and inferior mediastin...
The inferior mesenteric artery (IMA) is one of the three non-paired major visceral arteries in the abdominal cavity arising from the abdominal aorta and supplying the hindgut. It is the smallest of the three anterior visceral branches of the abdominal aorta.
Inferior mesenteric artery aneurysms are among the rarest of all visceral artery aneurysms.
Aneurysms of the inferior mesenteric artery (IMA) only account for <1% of all visceral artery aneurysms 1,2. These aneurysms are more common in men than in women 3.
The inferior mesenteric vein drains blood from the distal portion of the colon as well as the rectum (i.e. the hindgut).
Origin and course
The inferior mesenteric vein drains the mesenteric arcade of the hindgut (comprising of distal transverse, descending, and sigmoid colon). ...
The inferior pancreaticoduodenal artery is the first branch of the superior mesenteric artery (SMA), though it often arises from the first jejunal branch.
It anastomoses with branches of the superior pancreaticoduodenal artery (from the gastroduodenal artery) and it supplies the head of the pan...
The inferior petrosal sinus is one of the dural venous sinuses. It is often a plexus of venous channels rather than a true sinus and drains blood from the cavernous sinus to the jugular foramen (pars nervosa) or sometimes via a vein which passes through the hypoglossal canal to the suboccipital ...
The inferior phrenic arteries (IPA) are paired branches of the abdominal aorta / coeliac trunk supplying the diaphragm. Their importance lies with the fact that the right IPA is the most common extrahepatic arterial supply of a hepatocellular carcinoma.
origin: abdominal aorta or coel...
The inferior rectal artery is an artery that supplies the lower anal canal including the external anal sphincter.
origin: from internal pudendal artery, just after it enters the pudendal canal
course: runs anteromedially through the ischioanal fossa to reach the deep portion of the ex...
The inferior sagittal sinus is one of the dural venous sinuses and runs along the inferior edge of the falx cerebri. It runs from front to back (same as the superior sagittal sinus) and drains into the straight sinus. It receives tributaries from the falx itself as well as some small veins from ...
The inferior thoracic aperture connects the thorax with the abdomen.
The inferior thoracic aperture is irregular in shape and is more oblique and much larger than the superior thoracic aperture. The diaphragm occupies and closes the inferior thoracic aperture, thereby separating ...
The inferior thyroid artery is a branch of the thyrocervical trunk (85%) or subclavian artery (15%) and ascends to enter the thyroid gland on its posterior surface, as well as supplying both the superior and inferior parathyroid glands 1. The nerve is closely related to the ascending limb of the...
The inferior ulnar collateral artery is a vessel arising from the brachial artery at the distal-most part of the upper arm.
origin: branch of the brachial artery superior to the medial epicondyle 1
location: distal lower arm
supply: brachialis, biceps brachii, and coracobrachialis 1
The inferior vena cava (IVC) drains venous blood from the lower trunk, abdomen, pelvis and lower limbs to the right atrium of the heart.
The IVC is formed by the confluence of the two common iliac veins at the L5 vertebral level. The IVC has a retroperitoneal course within the ab...
Inferior vena cava filter, or just IVC filter, is an endovascular device which is typically placed in the infrarenal inferior vena cava (IVC) to prevent pulmonary embolism in selected patients. This procedure is most often performed by interventional radiologists under fluoroscopic guidance.
Inferior vena caval (IVC) thrombosis is an essential diagnosis while evaluating any neoplastic lesion, or portal hypertension. It is also important to differentiate bland thrombus from tumour thrombus.
Patient can present with many features which include
bilateral pedal oede...
Inferior vena cava (IVC) webs are an uncommon condition characterised by obstruction of the hepatic segment of the inferior vena cava by a membrane or fibrous band. This is often associated with occlusion of one or more of the hepatic veins.
If there is hepatic vein invol...
The inferior vesical artery is a branch of the anterior division of the internal iliac artery.
Some texts state it is only present in males and may be replaced by a vaginal artery in females. Note, the vaginal artery which is most commonly described, is often a branch of the uterine artery.
The inferolateral trunk, along with the meningohypophyseal trunk, is a branch of the C4 segment of the internal carotid artery. It is identified in up to 80% of dissection specimens but is less frequently seen on imaging.
It is also referred to as the artery to the inferior cavernous sinus, ari...
Inflammatory abdominal aortic aneurysm (IAAA) is a variant of abdominal aortic aneurysm (AAA) characterised by inflammatory thickening of the aneurysm wall, perianeurysmal fibrosis and adherence to surrounding structures.
They account for ~5 to 10% of all AAAs.
The infraorbital artery is a branch of the third part of the maxillary artery. It runs through the inferior orbital fissure, orbit, infraorbital canal then the infraorbital foramen. Here it gives off the anterior superior alveolar artery which supplies the anterior teeth and the anterior part of...
An infundibulum (plural: infundibula) is a conical outpouching from an artery (usually intracranial), with a broad base narrowing to an apex from which a vessel originates. The most common location for an infundibulum is the origin of the posterior communicating artery (PCOM) from the supraclino...
Infusothorax is a complication of central venous catheter malposition where the catheter tip is located in the pleural space and the infusion of the fluid collects inadvertantly in the pleural space in the form of a pleural effusion. Longer term complications depend on the fluid being infused.
Innominate artery compression syndrome, also known as brachiocephalic artery compression syndrome, is a rare cause of tracheal stenosis that occurs in the paediatric population.
It can only occur in the presence of an aberrantly positioned thymus that forces the aortic arch or innomi...
An inter-arterial course of the left coronary artery is defined as origination of the left main or left anterior descending coronary artery from the right coronary sinus of Valsalva, with a course between the ascending aorta and the pulmonary artery trunk.
An inter-arterial course...
Inter-arterial course of the right coronary artery (RCA), also known as a malignant variant, may occur if the right coronary artery has an aberrant origin from the the left coronary sinus. It is an uncommon anomaly with potential risk of cardiac ischaemia.
When the right coronary artery arises ...
The intercavernous sinus (anterior and posterior) are dural venous sinuses and connect the left and right cavernous sinuses, along with the basilar venous plexus. They lie in the anterior and posterior borders of the diaphragma sellae. Additional small venous sinuses in the base of the pituitary...
The internal carotid artery (ICA) is a terminal branch of the common carotid artery.
It arises most frequently between C3 and C5 vertebral level, where the common carotid bifurcates to form the internal carotid and the external carotid artery (ECA).
Variations in origin...
Internal carotid artery dissection, like arterial dissection elsewhere, is a result of blood entering the media through a tear in the intima 1 and is a common cause of stroke in younger patients.
Dissection may occur at any age, but is a common cause of stroke in young patients (2...
The internal carotid artery segments, according to the Bouthillier classification, can be recalled by the following mnemonic:
C'mon Please Learn Carotid Clinical Organizing Classification
C: cervical segment
P: petrous segment
L: lacerum segment
C: cavernous segment
C: clinoid se...
The internal cerebral veins are paired, paramedian veins which course posteriorly along the roof of the third ventricle, between the two leaves of the velum interpositum.
Each is formed at the foramen of Monro by the confluence of the choroidal vein (draining the choroid plexus o...
The internal iliac artery (also known as the hypogastric artery) is the smaller terminal branch of the common iliac artery. It supplies the pelvic walls, pelvic viscera, external genitalia, perineum, buttock and medial part of the thigh.
The common iliac artery bifurcate...
The internal iliac vein (IIV) represents the union of veins and venous plexuses draining the pelvic viscera, pelvic wall, external genitalia, perineum, buttocks and medial thigh.
Above the greater sciatic notch.
Course and termination
Ascends out of pelvis to meet the...
The internal jugular vein (IJV) is the major venous return from the brain, upper face and neck.
Origin and course
It is formed by the union of inferior petrosal and sigmoid dural venous sinuses in or just distal to the jugular foramen (forming the jugular bulb). It descends in t...
A useful mnemonic to remember the branches of the internal jugular vein is:
Medical Schools Let Fun People In
From inferior to superior:
M: middle thyroid vein
S: superior thyroid vein
L: lingual vein
F: facial vein
P: pharyngeal vein
I: inferior petrosal sinus
The internal palpebral arteries, or medial palpebral arteries, are branches of the ophthalmic artery, with superior and inferior medial palpebral branches arising opposite the trochlear of the superior oblique muscle.
The internal palpebral arteries enter the superior and inferio...
The internal pudendal artery is a branch of the anterior division of the internal iliac artery and is the primary supply of the perineum. It is a larger vessel in males than in females.
origin: anterior division of internal iliac artery
location: pelvis, gluteal region, perineum
The internal pudendal veins are the set of accompanying veins to the internal pudendal artery draining the perineal region to empty into the internal iliac vein.
inferior rectal veins
penile bulb and scrotum vein
clitoris and posterior labial vein
The internal thoracic artery (previously called the internal mammary artery) supplies the anterior body wall and its associated structures from the clavicles to the umbilicus.
The internal thoracic artery arises from the first part of the subclavian artery in the base of...
The interosseous recurrent artery is a branch of the posterior interosseous artery just after its origin, within the proximal aspect of the posterior compartment of the forearm. It courses proximally between the lateral epicondyle of the humerus and olecranon of the ulna to anastomose with the m...
An interscalene brachial plexus block is indicated for procedures involving the shoulder and upper arm.
Ultrasound-guided brachial plexus nerve blocks entered the literature in 1989, when Ting et al. detailed their success with axillary nerve blocks in 10 patients 3.
This is a basic article for medical students and other non-radiologists
Intestinal ischaemia refers to vascular compromise of the bowel which in the acute setting has a very high mortality if not treated expediently. Diagnosis is often straight forward provided appropriate imaging is obtained. ...
Intimal hyperplasia is not a true disease, but a physiologic healing response to injury to the blood vessel wall. It is the bane of endovascular intervention and vascular surgery.
When the endothelium is injured, endothelial cells release inflammatory mediators that trigger platelet aggregatio...
Intra-aortic balloon pumps (IABP) are used in the intensive care setting to provide haemodynamic assistance to patients in cardiogenic shock.
Function and physiology
The device is comprised of a catheter introduced via a femoral artery sheath, which extends retrogradely to the proximal descend...
Intra-atrial course of the right coronary artery is an uncommon anatomic variation in the course of the right coronal artery, usually involving the mid and distal segments, where the vessel partially or completely courses through the right atrial chamber.
It is usually asymptomatic and clinical...
Intracranial arteries have unique structure when compared to extracranial vessels of similar size: see general histology of blood vessels entry.
Proximal larger arteries
The proximal arteries, arising from the internal carotid and vertebral arteries have differing distribution of elastic fiber...
Intracranial arterial variants, of which there are many, are collectively common. Their clinical significance may be variable but knowledge and recognition of these variants is fundamental, especially if surgical or endovascular treatments (e.g. for acute stroke, aneurysms or other vascular path...
Intracranial mycotic aneurysms, or intracranial infectious aneurysms, describe aneurysms arising from infection of the arterial wall of intracranial vessels.
See mycotic aneurysm for a general discussion on infectious aneurysms.
The epidemiology of intracerebral mycotic aneurysms...
Intratesticular varicocele is a rare entity, occurring in ~2% of symptomatic population.
It is defined as dilated intratesticular veins seen in relation to the mediastinum testis and extending peripherally. It is usually seen in the presence of ipsilateral extratesticular varicocele....
Intravenous leiomyomatosis (IVLM) is characterised by the extension into venous channels of histologically benign smooth muscle tumour arising from either the wall of a vessel or from a uterine leiomyoma.
Intravenous leiomyomatosis should not be confused with benign metastasising l...
This is a basic article for medical students and other non-radiologists
Limb ischaemia is a relatively uncommon, but potentially limb (and life) threatening situation. There are many potential causes.
This is a summary article; we do not have a more in-depth reference articl...
Ischaemic colitis refers to inflammation of the colon secondary to vascular insufficiency and ischaemia. It is sometimes considered under the same spectrum as intestinal ischaemia. The severity and consequences of the disease are highly variable.
Ischaemic bowel is typically a dis...
Ischaemic stroke results from a sudden cessation of adequate amounts of blood reaching parts of the brain. Ischaemic strokes can be divided according to territory affected or mechanism.
Stroke is the second most common cause of morbidity worldwide (after myocardial infarction) and...
The Isikoff's view is a sonographic view which demonstrates the origins of the right and left renal arteries. It is taken in the longitudinal plane with the patient in the left lateral decubitus position 1.
Isolated periaortitis is a non-aneurysmal form of chronic periaortitis.
mesenteric arterial ischaemia: abdominal pain, diarrhoea, and gastrointestinal hemorrhage
renal artery stenosis: renovascular hypertension
Isolated unilateral absence of the pulmonary artery (IUAPA) is the congenital absence of the left or right pulmonary artery. When found in combination with other congenital vascular abnormalities it is known as unilateral absence of the pulmonary artery (UAPA).
The ISSVA classification of vascular anomalies is based on the initial classification published by Mulliken and Glowacki in 1982, and encompasses all vascular malformations and tumours in a framework of internationally consistent nomenclature. The classification was revised in 2014.
It is proba...
The ivy sign refers to the MRI appearance of patients with moya moya disease or moya moya syndrome. Prominent leptomeningeal collaterals result in vivid contrast enhancement and high signal on FLAIR due to slow flow. The appearance is reminiscent of the brain having been covered with ivy.
The jejunal and ileal branches of the superior mesenteric artery are variable in number.
They pass in the two layers of the mesentery to the jejunum and ileum and progressively divide and join in a series of anastomosing arcades. From the arcades, straight arteries (also known as the vasa recta...
The jugular bulb is the connection between the sigmoid sinus and the internal jugular vein.
The sigmoid and inferior petrosal sinuses empty into the jugular bulb, which continues as the internal jugular vein. It lies in the pars vascularis, which occupies the posterolateral aspe...
The internal jugular vein is a preferred site for venous access for large lumen, long-term central venous catheters for chemotherapy, haemofiltration and plasma exchange.
Typically, the right internal jugular is used as its vertical course straight down into the superior vena cava via the righ...
Kasabach-Merritt syndrome, also known as haemangioma thrombocytopenia syndrome, is a rare life-threatening disease found in infants in which a rapidly growing vascular tumour is responsible for thrombocytopenia, microangiopathic haemolytic anaemia and consumptive coagulopathy.
Kawasaki disease is a small to medium vessel vasculitis predominantly affecting young children. It can affect any body organ but there is a predilection for the coronary vessels.
Japan has the highest incidence in the world, with an annual incidence of 300/100,000 children under t...
Kawashima procedure is a palliative surgical procedure performed in cases of:
left isomerism and azygos continuation of the inferior vena cava
single functional ventricle
single atrium and common atrioventricular valve with or without regurgitation
It is performed by crea...
Kiesselbach plexus (Kiesselbach area or Little's area) is a vascular region of the anteroinferior nasal septum that comprises four arterial anastomoses:
anterior ethmoidal artery
a branch of the ophthalmic artery
a branch of the maxillary artery
greater palatine artery...
The term kissing carotids refers to tortuous and elongated vessels which touch in the midline. They can be be found in:
within the pituitary fossa
within sphenoid sinuses
within sphenoid bones
The significance of kissing carotids is two-fold:
may mimic intr...
Klippel-Trénaunay-Weber syndrome (KTWS) is a syndrome combination of capillary malformations, soft-tissue or bone hypertrophy, and varicose veins or venous malformations. It is considered an angio-osteo-hypertrophic syndrome.
KTS classically comprises a triad of:
port wine nevi
bony or soft t...
Kommerell diverticula occur in some anomalies of the aortic arch system. It usually refers to the bulbous configuration of the origin of an aberrant left subclavian artery in the setting of a right-sided aortic arch. However, it was originally described as a diverticular outpouching at the origi...
This article lists a series of labelled imaging anatomy cases by system and modality.
CT head: non-contrast axial
CT head: non-contrast coronal
CT head: non-contrast sagittal
CT head: angiogram axial
CT head: angiogram coronal
CT head: angiogram sagittal
MR head: T2 axial
The labyrinthine artery, also known as the auditory artery or internal auditory artery, is a long and slender artery that is the main arterial supply to the vestibular apparatus and cochlea.
It usually originates from the AICA (~85%), although it can also branch from the basilar artery (~15%), ...
The lacrimal artery is a branch of the ophthalmic artery that supplies the lacrimal gland.
The lacrimal artery travels along the upper border of the lateral rectus muscle with the lacrimal nerve to supply the lacrimal gland as well as the eyelids and conjunctiva.
The term large vessel vasculitis (LVV) usually denotes the spectrum of primary vasculitides that causes chronic granulomatous inflammation predominantly involving the aorta and its major branches.
The two major entities in this group are
giant cell arteritis (GCA): affects older individuals (t...
The Lasjaunias classification, at the time of writing (mid 2016), is one of the two commonly used systems for classifying vein of Galen malformations. It relies on dividing the entity into choroidal or mural types, depending on the number and origin of feeding arteries.
The lateral circumflex femoral artery (LCFA) is a branch of the profunda femoris that arises soon after the medial circumflex femoral artery. While the medial circumflex runs posteriorly around the femoral neck, the lateral circumflex courses laterally from its origin and anterior to the femoral...
The lateralised internal carotid artery is an anatomic variation of the course of the horizontal internal carotid artery (ICA). It can be visualised on CT by its more posterolateral entrance to the skull base and protrusion into the anterior mesotympanum. It may result in pulsatile tinnitus.
The lateral lenticulostriate arteries arise from the proximal middle cerebral artery (MCA) and supply the lateral portion of the putamen and external capsule as well as the upper internal capsule.
They are longer (almost twice the diameter) and more numerous than the medial lenticulostriate art...
The lateral posterior choroidal artery may be a singular structure or exist as multiple lateral posterior choroidal arteries. In both cases, they arise from the P2 segment of the PCA, just distal (and lateral) to the medial posterior choroidal arteries. In some cases, they may arise from one of ...
The lateral sacral artery is one of three branches of the posterior division of the internal iliac artery.
origin: from the posterior division of the internal iliac artery in the pelvis
branches: superior and inferior sacral arteries
supply: sacral meninges, pirifor...
The lateral thoracic artery is a branch of the second part of the axillary artery.
Origin and course
The lateral thoracic artery originates from the medial surface of the axillary artery, posterior to the distal part of pectoralis minor. It courses inferomedially along the infe...
The lateral umbilical folds are raised ridges of parietal peritoneum in the deep aspect of the anterior abdominal wall overlying the inferior epigastric vessels. The paired folds originate medial to the deep inguinal ring and end at the arcuate line on the posterior aspect of the anterior abdomi...
The left anterior descending (LAD) artery, also known as the anterior interventricular branch, is a branch of the left coronary artery.
It descends along the inteventricular groove.
It can be divided into proximal, mid and distal segments and this helps to differentiate the nam...
The left colic artery is the first branch of the inferior mesenteric artery.
It ascends retroperitoneally, dividing into two branches:
passes anteriorly to the left kidney, then enters the
transverse mesocolon, and passes superiorly to supply the upper part of the...
The left gastric artery is the smallest and first branch of the coeliac artery.
It passes superiorly, giving off an oesophageal branch to the distal oesophagus, then enters the lesser omentum to pass along the lesser curvature of the stomach. Anastomoses along the lesser curvature with the r...
The left gastric vein (also known as the coronary vein) drains both gastric walls. It forms a loop with the right gastric vein at the lesser curvature of the stomach. The left gastric vein travels in the lesser omentum to drain in the portal vein. It also communicates with the lower oesophageal ...
The left gastroepiploic artery (LGA) is one of the branches of the splenic artery.
The LGA runs within the two layers of the greater omentum to the right along the greater curvature of the stomach, approximately 1 cm from the gastric wall before it anastomoses with the ri...
The left hepatic artery (LHA) is formed when the proper hepatic artery (PHA) bifurcates. The hepatic arteries provide 25% of the blood supply and 50% of the oxygen supply to the liver.
The PHA bifurcates into the left and right hepatic arteries at or before reaching the porta hep...
The left main coronary artery (LMCA) or left coronary artery (LCA) is one of the two main arteries that supply the heart with oxygenated blood.
It is a branch of the ascending aorta, with its normal origin in the left aortic sinus, just superior to the aortic valve 1-2.
When a central venous catheter that is supposed to project over the superior vena cava is abnormally located to the left of the mediastinum a limited differential of left paramediastinal catheter position should be considered 1:
located within a vein
left sided superior vena cava
The left pulmonary artery (LPA) is one of the branches of the pulmonary trunk, branching at the level of the transthoracic plane of Ludwig. It is shorter than the right pulmonary artery and represents a direct posterior continuation of the pulmonary trunk. It arches posterosuperiorly over the su...
A left-sided superior vena cava (SVC) is the most common congenital venous anomaly in the chest, and in a minority of cases can result in a right-to-left shunt 3-4.
A left-sided SVC is seen in 0.3-0.5% of the normal population and in ~5% of those with congenital heart disease 3. I...
The left superior intercostal vein drains the left posterosuperior hemithorax and is considered to be part of the azygos venous system even though it does not directly drain into the azygos vein.
Origin and course
The left superior intercostal vein forms by the union of the 2nd...
Left ventricular assist devices (LVAD) are surgically implanted devices that aid pumping blood in patients with severe refractory cardiac failure. It may be used as a bridge to cardiac transplantation, or as destination therapy in patients who are not a transplant candidate.
Left ventricular pseudoaneurysms are false aneurysms that result from contained myocardial rupture, and are a rare complication of a myocardial infarction (MI). They should not be confused with left ventricular aneurysms, which are true aneurysms containing all the layers (endocardium, myocardiu...
Leiomyosarcomas (LMS) are extremely rare malignant neoplasms that originate from smooth muscle cells and may be considered the malignant counterpart of a leiomyoma. They are classified as a soft tissue tumour and account for ~8% of malignant soft tissue tumours 10.