Abdominal and pelvic anatomy encompasses the anatomy of all structures of the abdominal and pelvic cavities.
This anatomy section promotes the use of the Terminologia Anatomica, the global standard for correct gross anatomical nomenclature.
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.
origin: continuation of descending thoracic aorta at T12
course: descends anterior and slightly to th...
Abdominal aortic aneurysms (AAA) are focal dilatations of the abdominal aorta measuring 50% greater than the proximal normal segment, or >3 cm in maximum diameter.
represent the tenth most common cause of death in the Western world
prevalence increases with age
~10% patients old...
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.
This is a basic article for medical students and other non-radiologists
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.
This is a summary article; read more in o...
Abdominal aortic injuries are a very rare form of traumatic aortic injury 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 freque...
This is a basic article for medical students and other non-radiologists
Abdominal radiology curriculum for medical students is broadly split into content that refers to imaging (the test and findings) and conditions that are considered key for this stage of training.
Some non-abdominal conditi...
Abernethy malformations are rare vascular anomalies of the splanchnic venous system. They consist of congenital portosystemic shunts and result from persistence of the embryonic vessels.
Type I malformations are thought to occur only in females, while type II have a male predomin...
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 characterized by the left pulmonary artery arising from the right pulmonary artery and passing above the right main bronchus and in between the trachea and esophagus to reach the left lung. It may lea...
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-esophageal symptoms...
An absent infrarenal inferior vena cava can be congenital, due to the failure of development of the posterior cardinal and supracardinal veins, or acquired, as a result of intrauterine or perinatal inferior vena cava thrombosis.
It is an extremely rare anomaly.
The accessory appendicular artery, also known as the artery of Seshachalam, is a branch of the posterior cecal artery. It 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%) and are bilateral in ~10% of the population 7. Their proper identification is of utmost importance for surgical planning prior to live donor transplantation 2,3 and renal artery embolization for various reasons ...
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 hematoma
penetrating atherosclerotic ulcer
Acute occlusion of the basilar artery may cause brainstem or thalamic ischemia 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 (NSTEMI)
Acute superior mesenteric artery occlusion, which can then result in an acute mesenteric ischemia, 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 ischemia. Often despite thrombosis of the SMV, small bowel necrosis does not occur, presumably due to persistent arterial supply and some venous drainage via collaterals.
For a general discussion refer to...
The adrenal glands are supplied by three adrenal (suprarenal) arteries:
superior adrenal artery: arises from ipsilateral inferior phrenic artery
middle adrenal artery: arises from lateral side of abdominal aorta
inferior adrenal artery: arises from the ipsilateral renal artery
Adrenal hemangiomas are rare benign tumors 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 most ...
Adrenal lymphangiomas, also known as cystic adrenal lymphangiomas, are rare, benign cystic adrenal lesions.
Adrenal lymphangiomas are extremely rare; prevalence is estimated at 0.06% 8. They can occur at any age, with a peak incidence between the 3rd and 6th decades of life. Accor...
The venous drainage of the adrenal (suprarenal) glands is typically comprised of a single vein draining each adrenal gland. Like the gonadal veins each side drains differently:
left suprarenal vein drains into the left renal vein 1.
right suprarenal vein drains directly into the inferior vena ...
Adrenal vein sampling (AVS) is a procedure where blood is collected from the adrenal veins via catheter to confirm autonomous hormone production, if it is unilateral or bilateral, and to guide further treatment.
AVS is commonly performed in primary aldosteronism, being indicated to ...
AICA-PICA dominance refers to the principle that the cerebellar vascular territory supplied by the anterior inferior cerebellar artery and posterior inferior cerebellar artery have a reciprocal arrangement. That is the size of the AICA and the subsequent territory it supplies is inversely propor...
Alpha fetoprotein (AFP) is an important plasma protein synthesised by the yolk sac and fetal liver. In adults its main utility is as a tumor marker, primarily for hepatocellular carcinoma or teratoma. Functionally it is the fetal homologue of albumin, i.e. it acts as a major carrier protein in t...
Amniotic fluid embolism 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 for radiologists and imaging specialists.
Head and neck anatomy
Abdominal and pelvic anatomy
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)
Aneurysms of the portal vein are extremely rare and represent only 3% of all aneurysms of the venous system 1.
Most patients are asymptomatic but may present with nonspecific abdominal pain as a major symptom 2-4.
Both congenital and acquired causes have been ...
Angiosarcomas (like hemangiopericytomas and haemangioendotheliomas) are tumors 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 di...
The angular vein drains the anterior region of the scalp 1. It is formed by the union of the supratrochlear and supraorbital veins and becomes the facial vein 1,2,3.
The angular vein is formed at the medial canthus as the supratrochlear vein and supraorbital vein unite 1,2. The a...
Ankle brachial index (ABI) is a means of detecting and quantifying peripheral arterial disease. It can be performed in conjuction with ultrasound for better results.
Many patients with peripheral arterial disease may be asymptomatic (~20-50%), but they may also present with
Annulo-aortic ectasia refers to a proximal dilatation of the aortic root at the level of the aortic annulus, it is also the same level as the 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 ischemia 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 severe of such anomalies.
There are two forms, based on onset of disease, each of which has differe...
Anomalous systemic arterial supply to normal lung is an anatomical variant where a portion of the lung (usually a basal segment) gets supplied by a systemic vessel without a distinct pulmonary sequestration.
It was traditionally (perhaps inappropriately since not a true sequestrati...
The anterior cardiac veins are a group of parallel coronary veins that course over the anterior surface of the right ventricle, draining it and entering directly into the right atrium. They may occasionally drain into the small cardiac vein.
The anterior cardinal veins are paired transient embryologic venous vessels which deliver venous return to the heart starting at about 4 weeks of gestation 1.
The anterior cardinal veins begin their embryological development as symmetric venous channels draining blood from the cr...
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 ischemic 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 characterized 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. Approximately 4 mm in length, it demarcates the junction between the A1 and A2 segments of the anterior cerebral artery.
The anterior ethmoid artery is a branch of the ophthalmic artery. It supplies the anterior and middle ethmoidal sinuses, frontal sinus, the lateral nasal wall and the nasal septum (see nasal cavity).
It traverses the anterior ethmoidal foramen with the anterior ethmoidal nerve (w...
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 ischemic cerebellar strokes 2.
AICA stroke syndrome presents w...
The intercostal spaces are supplied by pairs of posterior and anterior intercostal arteries.
The 1st to 6th anterior intercostal arteries arise directly from the lateral aspect of the internal thoracic artery. The 7th to 9th arise from the musculophrenic artery, a branch of the i...
The anterior interosseous artery is one of the two branches of the short common interosseous artery (from the ulnar artery). The artery courses deep in the anterior compartment of the forearm on the anterior surface of the interosseous membrane along with the anterior interosseous nerve (from th...
The anterior jugular vein is a paired tributary of the external jugular vein.
It arises beneath the chin in the region of the hyoid bone or suprahyoid neck.
Origin and course
The anterior jugular vein has its origin as the confluence of several small superficial subma...
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 exte...
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 vertebral arteries (one of which is usually bigger than the other) anastamose in the midline to form a single anterior spinal artery at...
The anterior superior iliac spine is an important bony surface landmark and is the prominence is the most anterior part of the ilium. It can be palpated at the lateral end of the inguinal fold. Attachments include the inguinal ligament, sartorius and depending on which resource you read, the ten...
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 ...
The anterior ulnar recurrent artery is a recurrent branch of the proximal ulnar artery that ascends in the anterior medial aspect of the elbow, anterior to the medial epicondyle of the humerus to anastomose with the inferior ulnar collateral artery (from the brachial artery) and contribute to th...
Anti-neutrophil cytoplasmic antibody-associated vasculitides refer to a group of heterogeneous autoimmune diseases characterized by necrotizing vasculitides and positive anti-neutrophil antibody titers. 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 ischemic events occurring in patients who have circulating antiphospholipid antibodies.
Antiphospholipid syndrome is characterized by venou...
Antonio Egas Moniz (1874-1955) 1 was a pioneering Portuguese neurologist that is notable in radiology history for his development of cerebral angiography in 1927.
He is also known as the developer of prefrontal leucotomy (now better known as a lobotomy) for which he received a Nobel Prize in 1...
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 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 sinus of V...
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 useful 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 the most common form 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 th...
The aortic dissection detection risk score (ADD-RS) is a clinical decision tool that aids in grading the pretest probability of an acute aortic dissection. Scores range from 0-3, where 0 is classed as low risk, 1 is moderate risk and 2-3 is high risk 1.
The three domains in which pati...
The use of the aortic dissection detection risk score plus d-dimer is a proposed standardized strategy of safely ruling out the diagnosis of an acute aortic syndrome. Similar to how the pulmonary embolism rule-out criteria (PERC) negates the need for further workup of a pulmonary embolism.
The aortic hiatus is one of 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 midli...
Aortic intramural hematoma (IMH) is an atypical form of aortic dissection due to hemorrhage into the wall from the vasa vasorum without an intimal tear. It is part of the acute aortic syndrome spectrum.
Typically aortic intramural hematomas are seen in older hypertensive patients....
The aortic isthmus is the part of the aorta 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 partial sepa...
The aortic knob or knuckle refers to the frontal chest x-ray appearance of the distal aortic arch as it curves posterolaterally to continue as the descending thoracic aorta. It appears as a laterally-projecting bulge, as the medial aspect of the aorta cannot be seen separate from the mediastinum...
Aortic pseudoaneurysms typically occur as a result of trauma, a subset of traumatic aortic injury. 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...
Differentiation of aortic pseudoaneurysm from ductus diverticulum is critical, particularly in the trauma setting. A traumatic aortic pseudoaneurysm is a surgical emergency whereas a ductus diverticulum is a normal anatomy variant.
The following are differentiating features:
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
An aortic transection (also known as a traumatic aortic rupture) is a type of traumatic aortic injury. It is considered the second most common cause of death associated with motor vehicle accidents.
It occurs from a near-complete tear through "all the layers" of the aorta due to tra...
Aortitis refers to a general descriptor that involves a broad category of infectious and non-infectious conditions where there is inflammation (i.e. vasculitis) of the aortic wall.
The presentation is non-specific with fever, pain and weight loss.
Aortocaval 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 abdominal aortic aneurysm into the adjacent inferior vena cava occurs in <1% of all aneurysms and in ~3...
Aortoenteric fistula are pathologic communications between the aorta (or aortoiliac tree) and the gastrointestinal tract, and represent an uncommon cause of catastrophic gastrointestinal hemorrhage.
Aortic fistulas may be considered primary (associated with complicated abdominal aortic aneurysm...
Aortoiliac 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 you...
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 cecal 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 via multiple ascending branches.
The arc of Buhler (AOB) is a persistent embryonic anastomotic branch between the 10th and 13th ventral segmental arteries, resulting in a connection between the celiac artery and superior mesenteric artery (SMA). This arch is independent of both the gastroduodenal and dorsal pancreatic artery.