The anterolateral ligament of the knee (ALL) is a ligament that is thought to aid with rotational stability of the knee joint. Some think that its presence (or reconstruction) may result in better outcomes from ACL stabilization surgery 2. The ligament has also been implied in Segond fractures 3...
The term anterolisthesis refers to anterior displacement (forward slip) of a vertebral body relative to the one below.
Its severity can be graded by the Meyerding classification and its etiology classified according to the Wiltse classification.
The common causes of an anterosuperior mediastinal mass can be remembered by using the mnemonic:
T: thoracic aorta
T: terrible lymphoma
T: teratoma and germ cell tumors - see mediastinal germ cell tumors
Testicular cancer metastasis can represent a sixt...
Anthrax is a zoonosis caused by Bacillus Anthracis. There are four types of anthrax: inhalational anthrax (also known as woolsorter's disease and ragsorter's disease ), cutaneous anthrax, injection anthrax and intestinal anthrax.
The disease burden of anthrax decreased so dramatic...
Antibiotic-associated diarrhea can be broadly divided into two groups:
Clostridioides difficile colitis
The former is a life-threatening condition, requiring prompt diagnosis and treatment whereas the later is milder and self-limiting.
Both result from changes in the b...
Implanted antibiotic beads are a form of microbiological treatment inserted during orthopedic procedures to aid with the treatment of chronic infection. They are also used as a local treatment for osteomyelitis.
The beads are radiopaque, thus lending themselves to visualization on all imaging m...
Anti-GQ1b IgG antibody syndrome refers to a number of conditions which share autoantibodies to the ganglioside complex GQ1b, and have overlapping clinical spectrums.
The conditions believed to represent various clinical manifestations of a common immunological disorder include 1:
Anti jo 1 antibody positive interstitial lung disease refer to cases of interstitial lung disease occuring in the setting on anti Jo 1 antibody positivity.
Anti jo 1 antibody positivity has a recognized association with interstitial lung disease. This most commonly occurs in a setting of polymy...
Anti-MDA5 antibody-positive amyopathic dermatomyositis is a subtype of dermatomyositis where there is positivity to an anti-melanoma differentiation-associated gene 5 (MDA5) antibody. It has been reported to be associated with rapidly progressive interstitial lung disease (RP-ILD) resulting in h...
Anti-MOG associated encephalomyelitis represents a group of inflammatory demyelinating disorders united by the presence of IgG antibodies to myelin oligodendrocyte glycoprotein (MOG) that overlap with acute disseminated encephalomyelitis (ADEM), neuromyelitis optica spectrum disorder (NMOSD) and...
Antimuscarinics decrease bowel movements in pelvic MRI, and may be used for better image acquisition.
Usually, 20mg of hyoscine butylbromide IM/IV is administered prior to examination.
Benign prostatic hyperplasia
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...
Anti N-methyl-D-aspartic acid (NMDA) receptor encephalitis is an autoimmune encephalitis with antibodies against the NMDA receptors. It is sometimes considered a form of autoimmune limbic encephalitis. It usually affects young patients particularly young females, in about 60% of whom ovarian ter...
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...
Pulmonary involvement in antiphospholipid syndrome is one of the most frequent arterial complications of antiphospholipid syndrome.
It is essentially related to pulmonary arterial microthrombosis and may cause a wide spectrum of conditions, which include 3-5:
Anti-synthetase syndrome (ASS) is a systemic, inflammatory, autoimmune disease that is characterized by inflammatory myositis, polyarthritis associated with interstitial lung disease (ILD) and anti-synthetase autoantibodies.
ASS can result from autoantibodies to eight of the aminoacy...
Antithrombin (AT) III deficiency (now simply called antithrombin deficiency) refers to a congenital lack of the endogenous anticoagulant antithrombin.
Antithrombin deficiency is considered the least common of the three main anticoagulant deficiencies (the other two being protein C...
The antler sign is an uncommon sign of lung torsion on CT where branches from the main pulmonary artery all arise from a single side, indicating twisting of the lobe or lung.
In the normal lung, the main pulmonary arteries are straight and lobar and segmental branches arise from it on both side...
Antley-Bixler syndrome (ABS), also known as trapezoidocephaly-synostosis syndrome, is a rare autosomal dominant or recessive condition characterized by craniosynostosis and extra-cranial synostoses. Mid-facial hypoplasia is also common.
It is a very rare condition with only 50 cas...
Antoine H Becquerel (1852-1908) was a French scientist renowned for his work and subsequent discovery into the evidence of radioactivity for which he was awarded a Nobel Prize.
Antoine Henri Becquerel was born on 15 December 1852 in Paris, France to a family of nobility and active s...
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...
Antopol-Goldman lesions are very rare presentations of subepithelial hemorrhage in the renal pelvis, presenting as discrete mass-like hematomas.
The cause of these lesions is uncertain, although long-term anticoagulation, non-steroidal anti-inflammatory drugs (NSAIDs) overuse, trauma...
Antral follicle count (AFC) or basal antral follicle count is a test performed to check a female individual's ovarian reserve.
A female is born with a lifetime supply of eggs and as she enters puberty these eggs develop. During and after puberty these follicles develop and are relea...
The antral nipple sign refers to redundant pyloric mucosa protruding into the gastric antrum and is seen in hypertrophic pyloric stenosis on ultrasound examination.
cervix sign of pyloric stenosis
target sign of pyloric stenosis
The antral pad sign is a feature seen on a spot radiograph of the upper gastrointestinal tract obtained with orally-administered contrast material. It refers to the extrinsic impression or indentation on the posteroinferior aspect of the antrum. The impression is generally arcuate and smooth, an...
Antrochoanal polyps (ACP) are solitary sinonasal polyps that arise within the maxillary sinus. They pass to the nasopharynx through the sinus ostium and posterior nasal cavity, enlarging the latter two.
Similar, less common, polyps can arise in the sphenoid sinus extending into the nasopharynx:...
An antrolith is a calcified mass within the maxillary sinus. The origin of the nidus of calcification may be extrinsic (foreign body in sinus) or intrinsic (stagnant mucus, fungal ball).
Most antroliths are small and asymptomatic. Larger ones may present as a chronic maxillary sinusitis with sy...
The AO classification of distal clavicular fractures along with the Neer classification system is one of the more frequently used classification systems when assessing distal clavicular fractures. The classification system, broken into three categories focuses on the displacement and pattern of ...
The AO classification of proximal humeral fractures, along with the Neer classification, is one of the most frequently used systems for classifying proximal humeral fractures.
The AO classification divides proximal humeral fractures into three groups, A, B and C, each with subgroups, and place...
The AO classification of sacral injuries aims to simplify and universalise the process of classifying sacral injuries and improve interobserver and intraobserver reliability.
The AO sacral classification is broken into three subsections that follow a hierarchical structure similar to the AO cla...
The AO classification of subaxial injuries aims to simplify and universalise the classification of subaxial cervical spine fractures and improve interobserver and intraobserver reliability.
Although its existence is widely known among the relevant subspecialty groups, its day-to-day use ...
The AO classification of upper cervical injuries aims to simplify and universalise the process of classifying upper cervical injuries and improve interobserver and intraobserver reliability.
Although in routine clinical practice, at least in many institutions, injuries will be described ...
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
An aortic arch view is one of the additional views performed on fetal obstetric ultrasound - fetal echocardiography. It is an oblique sagittal view which is obtained similar to a left anterior oblique angiogram or the sagittal arch view obtained in CT arteriography. The isthmus, after the origin...
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...
An aortic nipple is seen in about 10% of PA chest x-rays on the lateral surface of the aortic arch/aortic knob. It represents the left superior intercostal vein.
When prominent, superior vena cava obstruction should be considered as the left superior intercostal vein serves as a collateral path...
Aortic pseudoaneurysms typically occur as a result of trauma +/- intervention, a considered subset of traumatic aortic injury in the majority of cases. They can be acute or chronic.
Aortic pseudoaneurysms are contained ruptures of the aorta in which the majority of the aortic wall ha...
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 anatomic variant.
The following are differentiating features:
The aortic-pulmonary stripe is an uncommon feature of frontal chest radiographs and was first described by Keats in 1972 1.
It is formed by the interface of the pleural surface of the anterior segment of the left upper lobe contacting the mediastinal fat that is anterolateral to the pulmonary t...
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...
An aortic root abscess is a serious complication of infective endocarditis.
Abscesses tend to be saccular in shape, range from 1 to 3 cm in diameter. Depending on sinus of origin, extended beneath the main and right pulmonary arteries or into the interventricular...
Aortic root dilatation refers to abnormal enlargement of the aortic root which may be focally aneurysmal or a more diffuse ectasia.
Aortic root dilatation is often completely asymptomatic and found incidentally 2. In rare instances, it may present with a catastrophic comp...
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 trau...
The aortic valve (AV) is one of the four cardiac valves. It is the semilunar valve that allows blood to exit the left ventricle (LV). It opens during systole and closes during diastole. The valve has left, right and posterior cusps, the bases of which attach around the valve orifice to a fibrous...
Aortic valve calcification can be an important incidental observation thoracic radiography or CT imaging. It is considered a marker for clinically significant aortic stenosis.
According to some reports aortic valve calcification may be prevalent as an incidental finding up to 18% of...
Aortic valve regurgitation, also known as aortic valve insufficiency or aortic valve incompetence, is a valvulopathy that describes leaking of the aortic valve during diastole that causes blood to flow in the reverse direction from the aorta and into the left ventricle.
Aortic valve stenosis is the most common valvulopathy and describes narrowing of the opening of the aortic valve between the aorta and the left ventricle.
Aortic stenosis is the most common valvulopathy, present in up to one-quarter of all patients with chronic valvular heart dise...
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 recognized early, can lead to prompt diagnosis and assist in surgical planning.
The aortomitral continuity (also known as the aortomitral curtain, aorticomitral junction, intervalvular fibrous body) is a fibrous sheet located between the noncoronary and left coronary leaflets of the aortic valve and anterior leaflet of the mitral valve. It is attached by the left and right ...
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...
The aortopulmonary (aortic-pulmonary or AP) window (also known as APW, but see 'Terminology' below) is a radiological mediastinal space seen on frontal chest radiographs.
The term should also not be confused with an aortopulmonary septal defect, which is occasionally also called an...
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...
Aorto-ventricular tunnel (AVT) is an extremely rare form of congenital heart disease, representing an anomalous extracardiac communication between the ascending aorta and the left or right ventricles.
In most cases the anomalous communication is between the aorta and the left ventr...
The AO spine classification of thoracolumbar injuries is one of the more commonly used thoracolumbar spinal fracture classification systems and aims to simplify and universalise the process of classifying spinal injuries and improve interobserver and intraobserver reliability 3.
Unlike the othe...
The AO Spine classification systems is a group of imaging morphology-based classification system, combined with clinical factors for injury of spinal trauma. It is designed to be a simple and reproducible method of describing injury patterns.
At the time of writing (Oct 2018), the four publishe...
The Acute Physiology and Chronic Health Evaluation (APACHE) score is an illness severity score commonly used in critical care medicine to predict mortality upon admission to an intensive care unit.
It involves two sections - one assessing the severity of the acute illness and another...
Apert syndrome (also known as type I acrocephalosyndactyly) is a syndrome that is predominantly characterized by skull and limb malformations.
The estimated incidence is 1 case per 65-80,000 pregnancies.
increased paternal age has been proposed 6
Apgar score was originally described by Virginia Apgar (American anaesthesiologist, 1909-1974) in 1952.
Helpfully, her surname is also a useful mnemonic for remembering the 5 factors: each is graded as 0, 1 or 2 with a total possible score of 10. The lower the score the worse the prognosis.
Aphakia (less commonly aphacia) is the absence of the lens from the ocular globe.
surgical removal of a cataract (commonest cause)
Treatment and prognosis
Surgical insertion of an intraocular lens implant, in which case the aphakic appearance is calle...
Aphthoid ulcers are shallow ulcers of the gastrointestinal mucosa.
infective inflammatory conditions
noninfective inflammatory conditions
idiopathic granulomatous gastritis
Apical hypertrophic cardiomyopathy (AHCM or ApHCM), also known as Yamaguchi syndrome, is a rare form of hypertrophic cardiomyopathy which usually involves the apex of the left ventricle, rarely involves the right ventricular apex, or involves both apices.
Historically, this condit...
The apical ligament is a small ligament that joins the apex (tip) of the dens of C2 to the anterior margin (basion) of the foramen magnum. It is the weak, fibrous remnant of the notochord and does not contribute significantly to stability.
The more posterior alar and cruciate ligaments are stro...
Handy mnemonics to remember common apical lung diseases are:
CARPETS (anagram of SET CARP)
E: eosinophilic pneumonia
C: cystic fibrosis
A: ankylosing spondylitis
R: radiation pneumonitis
Apical periodontitis refers to a spectrum of diseases that occur around the tooth apex these can include 1:
periapical (radicular) cyst
Apical periodontal disease of the maxillary teeth can extend into the maxillary sinuses with resultan...
Apical pleural cap refers to a curved density at the lung apex seen on chest radiograph.
The frequency of apical pleural thickening increases with age 3.
It arises from a number of causes:
idiopathic: chronic ischemic etiology is favored f...
The apical zone is one of the four chest radiograph zones and an important location for missed diagnoses when reporting a frontal chest radiograph and makes up one of the "check areas". It is sometimes thought of as a subdivision of the upper zone.
Aplastic anemia is a rare hematopoietic stem-cell disorder. The condition results in pancytopenia and hypocellular bone marrow. Most cases are acquired, however, there are unusual inherited forms.
Aplastic anemia manifests as a marked reduction in the number of pluripotent hematopoie...
Apocrine carcinoma of the breast is a rare variant of breast cancer. The diagnosis is mainly pathological as it is difficult to differentiate from other forms of breast cancer on imaging.
It accounts for about 4% of all cases. It is seen most often in females in the age group of 5...
Apocrine metaplasia of the breast is a benign breast condition and is sometimes considered part of or associated with fibrocystic change. It is a common finding in the female breast, particularly after the age of 25, and many regard it as a normal component of the breast.
Apodia is a rare non-syndromic transverse terminal lower limb defect characterized by the congenital absence of the foot and ankle. The remainder of the lower limb is present including both the tibia and fibular epiphyses. It can be unilateral or bilateral.
Apophyseal avulsion fractures of the pelvis and hip are relatively common among physically active adolescents and young adults.
Pelvic and hip apophyseal injuries typically occur in the 14 to 25 year age range.
Kicking sports, such as soccer, and gymnastics are frequen...
The apophyses (singular: apophysis) are the normal bony outgrowths that arise from separate ossification centers and eventually fuse with the bone in time. The apophysis is a site of tendon or ligament attachment, as compared to the epiphysis which contributes to a joint.
When unfused, they can...
The apophysis of the proximal 5th metatarsal (plural apophyses) lies laterally and is oriented longitudinally parallel to the shaft.
Apophysis of the fifth metatarsal base appears on plain radiographs at age 12 for boys and 10 for girls. Fusion of the apophysis to the metatarsal base usually oc...
Apoptosis (plural: apoptoses), also known as programmed cell death (PCD) is a term to describe the process of regulated cell death. This is in contrast to necrosis, which is unregulated cell death often secondary to external factors 1.
Apoptosis occurs in cells which are destined to die by acti...
Apostrophes are used according to standard English grammar rules. They are used for possessives and to indicate missing letters.
When using a possessive it's usually by adding "'s" at the end, e.g. "the patient's disease". Apostrophes should not be used for pluralisation, e.g. "apostrophes" an...
Apparent diffusion coefficient (ADC) is a measure of the magnitude of diffusion (of water molecules) within tissue, and is commonly clinically calculated using MRI with diffusion-weighted imaging (DWI) 1.
Diffusion-weighted imaging (DWI) is widely appreciated as an indispensable tool i...
Appendiceal carcinoids are rare overall but represent the most common tumor of the appendix. The appendix is also one of the most common (but not the most common) locations for gastrointestinal carcinoid tumors.
Appendiceal carcinoids can present as the obstructive cause...
Appendiceal diverticulitis (plural diverticulitides) is a rare condition in which there is acute inflammation of a diverticulum arising from the vermiform appendix.
Historically appendiceal diverticulitis has been thought to be a rare diagnosis. However a study from 2015 which ret...