Adrenal lesions cover a broad spectrum from benign to neoplastic entities. Due to increased use of cross-sectional imaging they are frequently detected as incidental lesions ("incidentalomas"). If found incidentally, please refer to the Management of incidental adrenal masses: American College o...
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...
Adrenal metastases are the most common malignant lesions involving the adrenal gland. Metastases are usually bilateral but may also be unilateral. Unilateral involvement is more prevalent on the left side (ratio of 1.5:1).
They are present at autopsy in up to 27% of patients with ...
Adrenal myelolipomas are rare benign, and usually asymptomatic, tumours of the adrenal gland characterised by the predominance of mature adipocytes.
On imaging, they usually present as large masses with a variable amount of fat-containing components.
Rare tumours with estimated ...
Adrenal pseudocysts account for ~40% of adrenal cysts and are more likely than simple adrenal cysts to be symptomatic.
Pseudocysts do not have an epithelial lining and typically arise after an episode of adrenal haemorrhage. There is an ~7% association with malignancy (e.g. from haem...
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 ...
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 washout can be calculated using the density value of an adrenal mass on non-enhanced, portal venous phase and 15 minutes delayed CT-scans. It is primarily used to diagnose adrenal adenoma.
[(HUportal venous phase) - (HUdelayed)] / [(HUportal venous phase) - (HUnon-enha...
Adrenocorticotropin independent macronodular adrenocortical hyperplasia (AIMAH) is considered a rare form of macronodular adrenal hyperplasia. It is an uncommon cause of primary adrenal hypercortisolism.
Patients with AIMAH tend to present 10 years earlier on average than...
Adrenoleukodystrophy (ALD) is an X-linked inherited metabolic peroxisomal disorder characterised by a lack of oxidation of very long chain fatty acids (VLCFAs) that results in severe inflammatory demyelination of the periventricular deep white matter with posterior-predominant pattern and early ...
Cervical lymphadenopathy in an adult can result from a vast number of conditions. They include:
from head and neck tumours
other neoplastic lesions
Adult chest radiograph common exam pathology is essential to consider in the build up to radiology exams. The list of potential diagnoses is apparently endless, but there are some favourites that seem to appear with more frequency.
When dealing with the adult chest radiograph in the exam settin...
A chest radiograph in the exam setting may contain a vast variety of pathology. However, consider the history and correlate the likely diagnoses that may be demonstrated on film. Furthermore, check your review areas to ensure that the abnormality isn't at the corner of the film.
The adult chest radiograph pathology checklist is just a pathology checklist of things not to miss when reviewing a chest radiograph, especially in the exam setting.
standard review areas
below the diaphragm
right descending pulmonary artery (like a l...
There are a number of adult chest radiograph set-pieces. These are based on common patterns of disease that are seen on chest radiographs. Make sure that you have relevant differentials for these appearances and a quick aural set-piece for them when they come up.
Adult cystic renal disease comprises multiple distinct hereditary and non-hereditary disease processes.
adult polycystic kidney disease (APCKD), a.k.a. autosomal dominant polycystic kidney disease (ADPCKD)
medullary cystic kidney disease
von Hippel-Lindau di...
Whenever you look at an adult elbow x-ray, review:
Check the anterior humeral line:
drawn down the anterior surface of the humerus
should intersect the middle 1/3 of the capitellum
if it doesn't, think distal humeral fracture
Adult granulosa cell tumour of the ovary is a type of ovarian sex cord / stromal tumour. They are by far the most frequent subtype of granulosa cell tumours of the ovary (95%) and are commoner than the juvenile granulosa tumour of the ovary.
Approximately two-thirds of this subtyp...
Adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP), also known as hereditary diffuse leukoencephalopathy with spheroids (HDLS) and pigmentary orthochromatic leukodystrophy (POLD), refers to a rare inherited autosomal dominant disease characterised by an adult-onset l...
Adventitious bursitis refers to inflammation associated with adventitious bursae.
Adventitious bursae are not permanent native bursae. They can develop in adulthood at sites where subcutaneous tissue becomes exposed to high pressure and friction.
When present in the foot...
Adynamic ileus is the failure of passage of enteric contents through the small bowel and colon that are not mechanically obstructed. Essentially it represents the paralysis of intestinal motility.
Patients may be asymptomatic or present with symptoms similar to a mechanic...
Afferent loop syndrome is an intermittent partial or complete mechanical obstruction of the afferent limb of a gastrojejunostomy.
The syndrome classically refers to obstruction of the upstream limb of a side-to-side gastrojejunostomy, but has also been used to refer to the biliopancreatic limb ...
Aflatoxins are naturally occuring mycotoxins that are produced by Aspergillus species, especially Aspergillus flavus. They are acutely toxic and carcinogenic.
High-level aflatoxin exposure can result acute aflatoxicosis with acute hepatic necrosis, resulting in cirrhosis, and po...
Human alpha fetoprotein (AFP) elevation may occur in a vast number of conditions:
liver tumours (hepatocellular carcinoma, hepatoblastoma)
<10 ng/ml is within normal limits
>20 ng/ml is above normal limits but has low specificity for tumor since it may occur in a setting of diffuse liver inju...
Human AFP (alpha-fetoprotein) reduction is seen in pregnancy where it can be associated with:
certain chromosomal anomalies
Cornelia de-Lange syndrome 2
Agatston score is a semi-automated tool to calculate a score based on the extent of coronary artery calcification detected by an unenhanced low-dose CT scan which is routinely performed in patients undergoing cardiac CT. Due to an extensive body of research, it allows for an early risk stratific...
The imaging characteristics of blood on MRI can be variable and change with the age of the blood.
In general, five stages of haematoma evolution are recognised:
isointense on T1
isointense to hyperintense on T2
acute (1 to 2 days)
Ageing blood on MRI is dependent on the varying MRI signal characteristics of haemorrhagic collections with time and can be very useful in correlating the imaging findings with the clinical picture. However, as it can be complicated to recall the MRI features of ageing blood through the five sta...
Agenesis of the diaphragm is a congenital diaphragmatic developmental anomaly where all or part of diaphragm fails to form. It can sometimes be thought of as an extreme form congenital diaphragmatic herniation 1.
The agenesis can either be unilateral or bilateral. Herniation of abdom...
Agenesis of the left hepatic lobe is a rare variation in liver anatomy. It is clinically asymptomatic and discovered during imaging or surgery.
absence of the left hepatic lobe (left of the falciform ligament, Couinaud segments II and III)
absence of left hepatic artery,...
Agenesis of the right hepatic lobe is a rare variation in liver anatomy.
absence of the right hepatic lobe
absence of right hepatic artery, right portal vein, and right hepatic biliary system
compensatory hypertrophy of the left hepatic lobe and caudate lobe
Agger nasi air cells are the most anterior ethmoidal air cells lying anterolateral and inferior to the frontoethmoidal recess and anterior and above the attachment of the middle turbinate. They are located within the lacrimal bone and therefore have as lateral relations the orbit, the lacrimal s...
Aggressive angiomyxomas are rare tumours that arise in the pelvis and typically cross the the levator ani muscles. Despite its name, it is essentially a benign tumour and the term "aggressive" is given due to a predilection for local recurrence. Only rarely does it metastasize.
Aggressive fibromatosis is a type of musculoskeletal fibromatosis. While it is a non-metastasising fibrous lesion, it is thought to be a true neoplasm that arises from the fascial and musculoaponeurotic coverings, sometimes at the site of a traumatic or post-surgical scar.
Aggressive granulomatosis post hip replacement is a potential complication of a hip joint replacement. Some authors use the same term for particle disease - if you are an expert on this we would love your help.
Aggressive granulomas consist of well organised connective tissue contain...
Agnosia is a neurological disorder characterised by an inability to identify an object despite both having knowledge of that object and sensory input that is functional. For example a patient with posterior cortical atrophy, which characteristically has visual agnosia, will be unable to identify...
This classification was proposed by Ahlback et al in 1968.
According to Ahlbäck system, knee joint osteoarthritis is classified as:
grade 1: joint space narrowing (less than 3 mm)
grade 2: joint space obliteration
grade 3: minor bone attrition (0-5 mm)
grade 4: moderate bone attrition (5-10...
Aicardi syndrome is a rare severe developmental disorder. It results from an X-linked genetic defect that is fatal in males and therefore only manifests in females (except for rare 47-XXY cases).
The typical presentation in infancy is with a triad of:
infantile spasms: salaa...
AIDS cholangiopathy refers to an acalculous, secondary opportunistic cholangitis that occurs in AIDS patients as a result of immunosuppression.
Characterised by multiple irregular strictures essentially indistinguishable from primary sclerosing cholangitis (PSC). There are four path...
AIDS defining illnesses are conditions that in the setting of a HIV infection confirm the diagnosis of AIDS, and do not commonly occur in immunocompetent individuals 2. According to the CDC surveillance case definition 1, they are:
bacterial infections: multiple or recurrent
Acquired immuno deficiency syndrome (AIDS) embryopathy is characterised by a group of dysmorphic features, which manifests either before or after birth in offsprings of women who are infected by HIV virus. The diagnosis however is in disfavour according to some authors 2.
AIDS-related diffuse large B-cell lymphomas are one of the immunodeficiency-associated CNS lymphomas, and in western countries represented a dramatic increase in primary CNS lymphoma during the HIV/AIDS epidemic of the 1980s, although the incidence is likely lower in patients treated with HAART ...
AIDS-related pulmonary lymphoma (ARPL) is classified as a distinct form of pulmonary lymphoma. Pulmonary involvement is a common extranodal site in AIDS-related NHL.
ARPL is typically a high-grade B-cell non-Hodgkin's lymphoma and the majority of patients have advanced HIV infection,...
Ainhum ("dactylolysis spontanea") is a rare cutaneous condition in which a hyperkeratotic band partially or totally encircles a digit. The constriction thins the underlying bone, which is then prone to fracture. Some cases result in autoamputation.
Some have suggested that the dis...
Air bronchogram refers to the phenomenon of air-filled bronchi (dark) being made visible by the opacification of surrounding alveoli (grey/white). It is almost always caused by a pathologic airspace/alveolar process, in which something other than air fills the alveoli. Air bronchograms will not ...
Air bronchogram describes gas within a bronchus that is surrounded by alveoli filled with fluid, pus or other material. It is a very useful sign because it is highly sensitive and specific for the presence of consolidation rather than collapse.
This is a summary article; read...
An air crescent sign describes the crescent of air that can be seen in invasive aspergillosis, semi-invasive aspergillosis or other processes that cause pulmonary necrosis. It usually heralds recovery and is the result of increased granulocyte activity.
In angioinvasive fungal infection, the no...
The air gap technique is utilised for the magnification mammography view.
Magnification mammography is a high dose imaging technique which is generally utilised as a follow-up to a standard mammogram image series when a focal area needs to be more clearly examined 1. The air gap technique is ut...
The utilisation of the air gap technique in general radiography is limited due to the need for equipment facilitation to create the air gap when it is not inherent in the standard technique.
Horizontal-beam lateral hip
There are many different methods of performing the horizontal beam lateral ...
Air space disease, or alveolar lung disease, is a process in which there is a filling of the lung's alveoli / acini.
lobar or segmental distribution
tendency to coalesce
bat's wing (butterfly) distribution...
An air space nodule is a small (few millimeters to 1 cm), ill-defined, nodular opacity that is often centrilobular in location and is non-specific, seen in many conditions. Commonly it represents a focal area of consolidation or peribronchiolar inflammation, and can indicate endobronchial spread...
Air space opacification is a descriptive term that refers to filling of the pulmonary tree with material that attenuates x-rays more than the surrounding lung parenchyma. It is one of the many patterns of lung opacification and is equivalent to the pathological diagnosis of pulmonary consolidati...
The differential for air space opacities is extensive, and needs to be interpreted in context of chronicity (previous imaging) and clinical context. It is therefore useful to divide airspace opacities as follows:
acute airspace opacities with lymph node enlargement
acute airspace opacities: un...
Air trapping in chest imaging refers to retention of excess gas (“air”) in all or part of the lung, especially during expiration, either as a result of complete or partial airway obstruction or as a result of local abnormalities in pulmonary compliance. It may also sometimes be observed in norma...
Air-space opacification is a descriptive term that refers to filling of the pulmonary tree with material that attenuates x-rays more than the surrounding lung parenchyma. It is equivalent to the pathological diagnosis of pulmonary consolidation.
This is a summary article; rea...
Airspace nodules are irregularly marginated nodular opacities with air bronchograms that tend to measure 8 mm in diameter. They are quite separate from pulmonary nodules that range in size, are homogeneous and well-defined (being surrounded by normal lung).
Airway foreign bodies in children are potentially fatal, which is why proper recognition is important. Unfortunately, delayed diagnosis is common.
Children under the age of four years are at increased risk of foreign body (FB) aspiration, with a slight male predominance 1.
Airway invasive aspergillosis refers to a form of invasive aspergillosis that affects the airways as the major or only feature.
It usually occurs in immunocompromised neutropenic patients, particularly AIDS patients. Aspergillosis affecting the airways as the major or only feature...
Airway pressure release ventilation (APRV) is an alternative mode for mechanical ventilation. It can be adopted as a method of alternative method for difficult-to-oxygenate patients with acute lung injury / acute respiratory distress syndrome (ALI/ARDS).
Its is usually not recommended in patien...
Alagille syndrome (AGS) is a congenital genetic multi-system disorder.
Infants typically present with symptoms relating to the liver where is it one of the most common causes of hereditary cholestasis.
AGS is inherited in an autosomal fashion with a mutation of...
Alanine is one of the compounds examined in MR spectroscopy. It resonates at 1.48 ppm chemical shift. It is elevated in meningiomas.
The alar ligaments join the lateral margins of the sloping upper posterior margin of the dens of C2 to the lateral margins of the foramen magnum (adjacent to the occipital condyles) and lie on either side of the apical ligament. The may be oblique or vertical and are thickest at the occipital at...
The Alberta stroke programe early CT score (ASPECTS) 1 is a 10-point quantitative topographic CT scan score used in patients with middle cerebral artery (MCA) stroke. Segmental assessment of the MCA vascular territory is made and 1 point is deducted from the initial score of 10 for every region ...
Alexander disease (AD), also known as fibrinoid leukodystrophy, is a rare fatal leukodystrophy, which usually becomes clinically evident in the infantile period, although neonatal, juvenile and even adult variants are recognised. As with many other diseases with variable age of presentation, the...
Aliasing artifact, otherwise known as undersampling, in CT refers to an error in the accuracy proponent of analogue to digital converter (ADC) during image digitisation.
Image digitisation has three distinct steps: scanning, sampling, and quantization.
When sampling, the brightness of each p...
Aliasing in MRI, also known as wrap-around, is a frequently encountered MRI artifact that occurs when the field of view (FOV) is smaller than the body part being imaged. The part of the body that lies beyond the edge of the FOV is projected onto the other side of the image.
This can be correcte...
Alien limb syndrome is a rare neurological phenomenon in which a patient has the impression that their limb does not belong to them and is controlled by some external force 1.
It can occur in a number of neurodegenerative diseases, typically those with cortical involvement, including:
All trans retinoic acid (ATRA) syndrome (more recently known as differentiation syndrome (DS)8) is a condition that can occur with patients with acute promyelocytic leukemia who are on therapeutic all-trans-retinoic acid (ATRA).
All-trans-retinoic acid (ATRA) is a normal constituent of plasma. ...
All-access pass to online courses are available to institutions who can purchase access to all Radiopaedia.org online courses for a flat per-user fee.
You can purchase all-access passes from your verified institution's page or directly from the all-access pass page. Find out more.
Allantoic cysts are a type of true cyst of the umbilical cord.
The allantois forms from the part of the fetal yolk sac that eventually becomes the primitive hindgut (the cloaca). The cloaca divides into the hindgut posteriorly and the urogenital sinus anteriorly. The allantois remain...
Allelic heterogeneity is a genetics term referring to same gene mutations resulting in different phenotypes 1. An example of a condition demonstrating allelic heterogeneity is Joubert syndrome and related disorders.
Allen and Ferguson classification is used for research purposes to classify subaxial spine injuries. It is based of the mechanism of injury and position of neck during injury. This classification was proposed by Allen and Ferguson in 19823 and at the time of writing (July 2016) remains the most ...
Allergic bronchopulmonary aspergillosis (ABPA) is at the mild end of the spectrum of disease caused by pulmonary aspergillosis and can be classified as an eosinophilic lung disease 2-4.
This entity is seen is almost only encountered in patients with longstanding asthma, and only o...
Allergic fungal sinusitis (AFS) is the most common form of fungal sinusitis and is common in warm and humid climates. On imaging, it usually presents as opacification and expansion of multiple paranasal sinuses, unilaterally or bilaterally, with content that is centrally hyperdense on CT. MRI sh...
Allgrove syndrome (also known as triple A syndrome) is an autosomal recessive condition that consists of three main findings:
Allodynia refers to pain due to a stimulus which does not normally provoke pain. Temperature or physical stimuli can provoke allodynia, and it often occurs after injury to a site.
The word allodynia is derived from from the Greek words άλλος (állos) meaning "other" and οδύν...
Alobar holoprosencephaly is a subtype of holoprosencephaly (HPE), and is the most severe of the classical three subtypes, with both semilobar and lobar holoprosencephaly having less severe clinical manifestations.
For a general discussion of epidemiology, clinical presentation, and pathology, p...
Alpha angle can refer to two different musculoskeletal measurements:
alpha angle (developmental dysplasia of the hip)
alpha angle (femoroacetabular impingement)
The alpha angle is a measurement used in the ultrasonographic assessment of developmental dysplasia of the hip (DDH).
The angle is formed by the acetabular roof to the vertical cortex of the ilium and thus reflects the depth of the bony acetabular roof. This is a similar measurement to the acet...
All nuclei with the atomic number Z>82, are considered unstable. These are considered “neutron rich” and undergo the decay process by emitting a particle containing two neutrons and two protons.
Alpha decay is the process in which an alpha particle (containing two neutrons and two protons) is e...
Alpha-thalassemia/mental retardation syndrome X-linked (ATRX) is an important genomic marker of gliomas. Loss/mutation of ATRX is almost never seen in patients with 1p/19q co-deletion (i.e. they are essentially mutually exclusive). Oligodendrogliomas will, therefore, have intact ATRX and 1p19q c...
Alpha-1 antitrypsin (A1AT) deficiency is a hereditary metabolic disorder and is the most common genetic cause of emphysema and metabolic liver disease in children. It results in the unopposed action of neutrophil elastase and subsequent severe basal pan lobular emphysema and respiratory symptoms...
Alport syndrome is an X-linked recessive disease characterised by:
sensory neural hearing loss: typically high frequency 2
anterior lenticonus: most common ocular abnormality; may result in cataracts
perimacular pigmentary changes
flecks around the fovea 2...
Mammographic screening detects early breast cancers and thereby reduces potential mortality. However, its sensitivity is inversely related to breast density 1.
Altered density between two mammograms can arise in a number of situations:
Affecting both breasts:
interval commencement/cessation ...
Alternating radiolucent and radiodense metaphyseal lines can be seen with a number of conditions and the differential diagnosis is wide:
growth arrest lines
rickets: especially those on prolonged treatment, e.g. vitamin D dependent rickets
Alternatives are part of multiple choice questions, comprising the options from which an examinee must choose the correct answer.
Each multiple choice question should have, ideally, 5 alternatives, one of which is the correct answer (the "key"). In some instances, 5 options are not appropriate...
The Alvarado score is a clinical decision rule and predictor of the likelihood of acute appendicitis:
right lower quadrant tenderness (+2)
elevated temperature (37.3°C or 99.1°F) (+1)
rebound tenderness (+1)
migration of pain to the right lower quadrant (+1)
nausea or vomitin...
Alveolar rhabdomyosarcomas are a type of rhabdomyosarcoma and accounts for 20-40% of all rhabdomyosarcomas 1-2. Unlike embryonal rhabdomyosarcomas, which are more common, these tumours occur in slightly older individuals, typically 10-25 years of age 1.
Although these tumo...
Alveolar sarcoidosis is an atypical pulmonary manifestation of sarcoidosis.
This appearance may be apparent in approximately 4% of those with pulmonary sarcoidosis on plain film 1 and up to 15% on CT 2.
This appearance is thought to result from the aggregation of a va...
The alveoli are tiny hollow air sacs that comprise the basic unit of respiration.
Alveoli are found within the lung parenchyma and are found at the terminal ends of the respiratory tree, clustered around alveolar sacs and alveolar ducts. Each alveolus is approximately 0.2 mm in ...
Alzheimer disease (AD) is a common neurodegenerative disease, responsible for 60-80% of all dementias, and imposing a significant burden on developed nations. It is the result of accumulation and deposition of cerebral amyloid-β (Aβ) and is the most common cerebral amyloid deposition disease.
Alzheimer type I glia are a type of glial cell. They are large multinucleated astrocytes encountered in glial tumours and progressive multifocal leukoencephalopathy (PML) 1.
Alzheimer type II glia are a type of glial cell. They are a pathological reactive astrocyte seen in the brain, unrelated to Alzheimer disease. They are seen most frequently in Wilson disease, but also in other systemic metabolic disorders, particularly those with elevated ammonia levels, typical...