Articles

Articles are a collaborative effort to provide a single canonical page on all topics relevant to the practice of radiology. As such, articles are written and edited by countless contributing members over a period of time. A global group of dedicated editors oversee accuracy, consulting with expert advisers, and constantly reviewing additions.

2,023 results found
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1p19q codeletion

1p19q codeletion stands for the combined loss of the short arm chromosome 1 (“1p”) and the long arm of chromosome 19 (“19q”) and is recognised as genetic marker predictive of therapeutic response (both chemotherapy and combined chemoradiotherapy) and overall longer survival in patients with diff...
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A-rings

A-rings are a type of distal oesophageal ring. They are above the B-ring and occur a few centimetres proximal to the gastro-oesophageal junction. They represent a physiological contraction of oesophageal smooth muscle covered by mucosa. A-rings are uncommonly symptomatic.
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Abdominal aortic aneurysm

Abdominal aortic aneurysms (AAA) are focal dilatations of the abdominal aorta that are 50% greater than the proximal normal segment or that are >3 cm in maximum diameter. Epidemiology Its prevalence increases with age. Males are much more commonly affected than females (with a male: female ...
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Abdominal aortic aneurysm rupture

Abdominal aortic aneurysm (AAA) rupture is a feared complication of abdominal aortic aneurysm and is a surgical emergency. Epidemiology Abdominal aortic aneurysms are common and affect ~7.5% of patients aged over 65 years 6. Clinical presentation The classical triad of pain, hypotension and ...
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Abdominal aortic injury

Abdominal aortic injuries are very rare and are much less common than thoracic aortic injury.  Epidemiology Aortic injury occurs in <1% of blunt trauma patients, with abdominal aortic injury representing only ~5% of all aortic injuries 1. Males are more frequently injured, with the median a...
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Abernethy malformation

Abernethy malformations are rare vascular anomalies of the splanchnic venous system. They comprise of congenital portosystemic shunts and result from persistence of the embryonic vessels.  Epidemiology Type I malformations are thought only to occur in females with type II having a male predile...
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Aberrant left pulmonary artery

Aberrant left pulmonary artery, also known as pulmonary sling, represents an anatomical variant characterised by the left pulmonary artery arising from the right pulmonary artery and passing above the right main bronchus and in between the trachea and oesophagus to reach the left lung. It may le...
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Absent ductus venosus

Agenesis of the ductus venosus (ADV) is a rare fetal vascular anomaly. According to the data obtained from the screening tests performed at 11-14 weeks of pregnancy, its incidence is reported to be 1/2500 (12). Pathology In the literature review on ductus venosus agenesis, Acherman et.al (13) ...
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Absent infrarenal inferior vena cava

An absent infrarenal inferior vena cava (IVC) can be congenital due to failure of development of the posterior cardinal and supracardinal veins, or acquired as result of intrauterine or perinatal inferior vena cava thrombosis. Epidemiology It is an extremely rare anomaly. Clinical presentatio...
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Acardiac twin

Acardiac twins (or recipient twins) are haemodynamically disadvantaged non-viable twins that undergo secondary atrophy in association with a twin reversed arterial perfusion sequence. Epidemiology Acardiac twinning is thought to affect 1 in 100 monozygotic twin pregnancies and 1 in 35,000 preg...
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Achalasia

Achalasia (primary achalasia) refers to a failure of organised oesophageal peristalsis with an impaired relaxation of the lower oesophageal sphincter (LOS), resulting in often marked dilatation of the oesophagus and food stasis. Obstruction of the distal oesophagus (often due to tumour) has been...
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Achilles tendinopathy

Achilles tendinopathy refers to a combination of pathological changes affecting the Achilles tendon usually due to overuse and excessive chronic stress upon the tendon. It can be seen both in athletes and non-athletes (weekend warriors). It 's hard to differentiate clinically from a paratendinop...
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Achilles tendon ossification

Achilles tendon ossification (ATO) is an uncommon condition and has characteristic bone formation within the Achilles tendon itself.  Epidemiology ATO is more common in males 4.  Pathology The aetiology is unknown but Achilles tendon ossification is seen both with previous macrotrauma of the...
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Achilles tendon xanthoma

Achilles tendon xanthomas are painless soft tissue masses occurring most commonly at the distal one-third of the tendon, usually bilaterally and symmetrically. Pathology It is characterised by localised accumulation of lipid laden macrophages, inflammatory cells and giant cells secondary to ch...
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Achondrogenesis

Achondrogenesis refers to a group of rare and extreme skeletal dysplasias. Epidemiology The estimated incidence is 1:40,000 with no recognised gender predilection. Pathology It is classified as an osteochondrodysplasias, meaning deficiency of both bone and cartilage development. Subtypes T...
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Achondroplasia

Achondroplasia is a congenital genetic disorder resulting in rhizomelic dwarfism and is the most common skeletal dysplasia. It has numerous distinctive radiographic features.  Epidemiology It occurs due to sporadic mutations in the majority of cases but can be inherited as an autosomal dominan...
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Acinic cell carcinoma of the lung

Acinic cell carcinoma of the lung (also known as a Fechner tumour) is a type of lung carcinoma of the salivary gland type. It is extremely rare especially when it presents in the form of a primary acinic cell carcinoma. Pathology Histologically, they are comprised of clear cells with abundant ...
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Acoustic schwannoma

Acoustic schwannomas (a.k.a. vestibular schwannomas) are relatively common tumours that arise from the vestibulocochlear nerve (CN VIII) and represent ~80% of cerebellopontine angle masses. Bilateral acoustic schwannomas are strongly suggestive of neurofibromatosis type 2 (NF2). These tumours c...
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Acquired cholesteatoma

Acquired cholesteatomas makeup 98% of all middle ear cholesteatomas and are almost always closely related to the tympanic membrane, from which most are thought to arise.  Clinical presentation The vast majority of acquired cholesteatomas develop as a result of chronic middle ear infection and ...
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Acquired cystic kidney disease

Acquired cystic kidney disease (ACKD) is a condition that occurs in patients with end-stage kidney disease (ESKD), especially when on dialysis treatment, and who do not have a history of other cystic renal disease.  Epidemiology Its incidence increases with the amount of time a patient is azot...
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Acrania anencephaly sequence

Acrania anencephaly sequence is the progression from a relatively normal-appearing brain (acrania) to an amorphous brain mass (exencephaly) to no recognizable brain tissue (anencephaly) 1. Epidemiology The acrania anencephaly sequence begins with acrania, which is the most common anomaly affec...
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Acromegaly

Acromegaly is the result of excessive growth hormone (GH) production in skeletally mature patients, most commonly from an adenoma of the pituitary. It most commonly affects adults in middle age and can result in severe disfigurement, serious complicating conditions, and premature death. It has ...
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Acute acalculous cholecystitis

Acute acalculous cholecystitis (AAC) refers development of cholecystitis either in a gallbladder without gallstones on in a gallbladder with gallstones where the stones are not the contributory factor to the development of cholecystitis. Epidemiology AAC usually occurs in critically ill or inj...
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Acute cholangitis

Acute cholangitis (or ascending cholangitis) is a form of cholangitis and refers to the acute bacterial infection of the biliary tree. It is a condition with high mortality and emergent biliary decompression is required.  Clinical presentation The classical presentation is Charcot triad of fev...
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Acute cholecystitis

Acute cholecystitis refers to the acute inflammation of the gallbladder. It is the primary complication of cholelithiasis and the most common cause of acute pain in the right upper quadrant (RUQ). Clinical presentation Constant right upper quadrant pain that can radiate to the right shoulder. ...
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Acute coronary syndrome

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 (non-STEMI) unstable...
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Acute disseminated encephalomyelitis

Acute disseminated encephalomyelitis (ADEM) as the name would suggest, is featured by a monophasic acute inflammation and demyelination of white matter typically following a recent (1-2 weeks prior) viral infection or vaccination 4,6. Grey matter, especially that of the basal ganglia, is also of...
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Acute eosinophilic pneumonia

Acute eosinophilic pneumonia (AEP) is a type of eosinophilic lung disease. It is diagnosed when the following combination clinical and radiographic findings occur 5,7: febrile illness of less than five days duration hypoxaemia diffuse alveolar or mixed alveolar-interstitial opacities on chest...
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Acute fatty liver of pregnancy

Acute fatty liver of pregnancy (AFLP) is a rare pregnancy-associated condition that tends to manifest in the 3rd trimester of pregnancy or early postpartum period. Epidemiology The estimated incidence is at around 1:7000-20,000 births.  Clinical presentation Patients may present with nausea,...
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Acute haemorrhagic leukoencephalitis

Acute haemorrhagic encephalomyelitis (AHEM), also known as acute haemorrhagic leukoencephalitis (AHLE), Hurst disease or Weston-Hurst syndrome, is a very rare form of demyelinating disease. It occurs sporadically and may be considered as the most severe form of acute disseminated encephalomyelit...
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Acute hypersensitivity pneumonitis

Acute hypersensitivity pneumonitis (AHP) refers to the acute form of hypersensitivity pneumonitis although this classification system has recently been challenged 4. For a general discussion of the condition, refer to the parent article. Clinical presentation Fever, chills, myalgia, headaches,...
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Acute idiopathic scrotal oedema

Acute idiopathic scrotal oedema (AISE) is a self-limiting condition characterised by marked oedema of the skin and dartos fascia without involvement of the deeper layers, testes, or epidydimis. It is an important condition to recognise in order to avoid unnecessary surgical exploration. Epidemi...
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Acute interstitial pneumonitis

Acute interstitial pneumonitis (AIP), also know as Hamman-Rich syndrome is a rapidly progressive non infectious interstitial lung disease of unknown aetiology. It is considered the only acute process of the idiopathic interstitial pneumonias. Epidemiology AIP tends to occur in those without pr...
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Acute invasive fungal sinusitis

Acute invasive fungal sinusitis is the most aggressive form of fungal sinusitis. It is seen particularly in immunocompromised patients and is the source of significant morbidity and mortality. It should be distinguished from the other two forms of invasive fungal sinusitis: chronic invasive fung...
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Acute liver failure

Acute liver failure (ALF) or fulminant hepatic failure (FHF) refers to sudden severe liver dysfunction from injury without underlying chronic liver disease (CLD), although sometimes ALF presents as decompensation of an unknown CLD.  Epidemiology ALF is rare, with < 1 case per 100,000 in the...
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Acute mastoiditis

Acute mastoiditis is largely a disease of childhood, and occurs when acute otitis media extends into the mastoid air cells.  Terminology When mastoiditis and acute otitis media occur concurrently, sometimes the term acute otomastoiditis is used.  When mucoperiosteal involvement evolves into b...
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Acute necrotic collection

Acute necrotic collections (ANCs) are an early, local complication of necrotising pancreatitis. Terminology The following are the latest terms according to the updated Atlanta classification to describe fluid collections associated with acute pancreatitis 1,2: fluid collections in interstitia...
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Acute pancreatitis

Acute pancreatitis refers to acute inflammation of the pancreas and is a potentially life threatening condition. The diagnosis of acute pancreatitis is made by fulfilling two of the following three criteria 8: acute onset of persistent, severe epigastric pain (i.e. pain consistent with acute p...
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Acute peripancreatic fluid collection

Acute peripancreatic fluid collections (APFC) are an early complication of acute pancreatitis that usually develop in the first four weeks. After four weeks, the term pseudocysts is used. The absence of necrosis differentiates APFCs from acute necrotic collections (ANC), that is, APFCs occur in ...
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Acute pyelonephritis

Acute pyelonephritis remains common and continues to have significant morbidity in certain groups of patients. Epidemiology The incidence of acute pyelonephritis parallels that of lower urinary tract infections: approximately five times more common in females with a sharp increase following pu...
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Acute superior mesenteric artery occlusion

Acute superior mesenteric artery occlusion, which can then result in an acute mesenteric ischaemia, can be a life threatening event related to the artery supplying the majority of the small bowel and right side of the colon.  Epidemiology  An acute occlusion is an uncommon event that typically...
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Acute superior mesenteric vein thrombosis

Acute superior mesenteric vein thrombosis is one of the less common causes of intestinal ischaemia.  For a general discussion refer to intestinal ischaemia.  Epidemiology Compared to acute superior mesenteric artery occlusion or ischaemia secondary to small bowel obstruction, acute superior m...
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Acyanotic congenital heart disease

There are numerous causes of acyanotic congenital heart disease and can be divided into those that have increased pulmonary vascularity (pulmonary plethora) and those that do not: increased pulmonary vascularity ventricular septal defect (VSD) atrial septal defect (ASD) atrioventricular sept...
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Adamantinoma

Adamantinomas are rare primary malignant bone tumours that in the vast majority of cases occur in the tibia of young patients.   Terminology In the past, ameloblastomas, which are benign and locally aggressive bone tumours of the mandible, were also known as adamantinomas of the mandible. Both...
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Adenocarcinoma in situ of lung

Adenocarcinoma in situ (AIS) of lung refers to a relatively new entity for a pre invasive lesion in the lung. This entity partly replaces the non invasive end of the previous term bronchoalveolar carcinoma. AIS is defined as a localized adenocarcinoma of less than 3 cm, that exhibits a lepidic p...
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Adenocarcinoma in situ, minimally invasive adenocarcinoma and invasive adenocarcinoma of lung

Adenocarcinoma in situ, minimally invasive adenocarcinoma and invasive adenocarincoma of lung are relatively new classification entities which now replaces the now defunct term bronchoalveolar carcinoma (BAC). In 2011 the International Association for the Study of Lung Cancer and other societie...
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Adenocarcinoma of duodenum

Duodenal adenocarcinoma is the most common primary malignancy of the duodenum. Epidemiology Adenocarcinoma is the most common primary malignant neoplasm of the duodenum. It represents 0.3% of all gastrointestinal malignancies. It accounts for  50-70% of small bowel adenocarcinomas occurring ei...
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Adenocarcinoma of the bladder

Adenocarcinoma of the bladder is rare, and accounts for only ~1% of all bladder cancers (90% are transitional cell carcinomas). Pathology Metaplasia of urinary bladder induced by chronic irritation or infection can lead to adenocarcinoma. Pathological types of adenocarcinoma of urinary bladder...
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Adenocarcinoma of the lung

Adenocarcinoma of the lung is one of the non-small cell carcinomas of the lung and is a malignant tumour with glandular differentiation or mucin production. This tumour exhibits various patterns and degrees of differentiation, including lepidic, acinar, papillary, micropapillary and solid with m...
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Adenoid cystic carcinoma

Adenoid cystic carcinoma (ACC) are a rare histological subtype of adenocarcinoma. Pathology ACCs are generally considered low grade 4. The tumors have notable tendency for perineural spread. Location They have wide distribution and mainly occur in relation to the airways, lacrimal glands and...
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Adenoid cystic carcinoma of lung

Adenoid cystic carcinoma (ACC) of lungs are a type of non small cell lung cancer. They are classified under lung carcinomas of the salivary gland type. Primary occurrance in the lung parenchyma is rare and in the thorax, they more commonly occur as adenoid cystic carcinoma of the tracheo-bronchi...
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Adenoid cystic carcinoma of salivary glands

Adenoid cystic carcinoma (ACC) of the salivary glands is the second most common malignancy involving the parotid and the most common involving minor salivary glands. Pathology ACCs arise more commonly in the minor salivary glands (~55%) than in the major salivary glands. They are locally aggre...
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Adenoid cystic carcinoma of the breast

Adenoid cystic carcinoma (ACC) of the breast is a rare subtype of breast cancer. Epidemiology They account for only 0.1-0.4% of all breast cancers. Pathology The tumour demonstrates a strikingly characteristic microscopic pattern similar to that of adenoid cystic carcinoma of the salivary gl...
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Adenoid cystic carcinoma of the tracheobronchial tree

Adenoid cystic carcinomas of the tracheobronchial tree are a type a low-grade tracheal tumour. They are considered the second most common primary tumour of the trachea. Epidemiology They are usually first recognized in patients in their 40s. There is no recognised gender predilection. Clinica...
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Adenoidal hypertrophy

Adenoidal hypertrophy or enlargement is common in childhood and is due to increase in size of the adenoid tonsils. Clinical presentation nasal congestion: adenoid facies chronic or recurrent otitis media due to their proximity to the Eustachian tubes swallowing difficulties speech anomali...
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Adenolipoma of thyroid gland

Adenolipoma of the thyroid gland (also known as a thyrolipoma or a thyroid hamartoma) is a benign rare fat containing thyroid lesion. These lesions are usually well encapsulated and are composed of varying degrees of thyroid glandular tissue and fat tissue; the amount of fat can markedly vary (...
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Adenoma-carcinoma sequence

The adenoma-carcinoma sequence refers to a stepwise pattern of mutational activation of oncogenes (eg. K-ras) and inactivation of tumour suppressor genes (eg. p53) that result in cancer. An oncogene is a gene that has the potential to cause cancer. In tumor cells these are often mutated or expre...
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Adenomatoid odontogenic tumour

Adenomatoid odontogenic tumours are rare and differ from most other dentition related lesions in that they more frequently occur in the maxilla. Epidemiology They are also seen more frequently in females, most frequently in the second decade of life.  Radiographic features They present as an...
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Adenomyomatosis of the gallbladder

Adenomyomatosis of the gallbladder is a hyperplastic cholecystosis of the gallbladder wall. It is a relatively common and benign cause of diffuse or focal gallbladder wall thickening. It is most easily seen on ultrasound and MRI.  Epidemiology Adenomyomatosis is relatively common, found in ~9%...
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Adenomyosis of the uterus

Adenomyosis of the uterus is a relatively common, benign uterine pathology. It is thought by many to be on the spectrum of endometriosis, with ectopic endometrial tissue in the myometrium. Adenomyosis may present with menorrhagia and dysmenorrhea. Ultrasound and MRI are imaging modalities that m...
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Adenosquamous carcinoma of lung

Adenosquamous carcinoma (ASC) of the lung is a rare type of non small cell lung cancer. Epidemiology It is thought to constituting 0.4-4% of cases non small cell lung cancer. Pathology The definition of adenosquamous carcinoma indicates a carcinoma showing components of adenocarcinoma and sq...
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Adhesive capsulitis of the shoulder

Adhesive capsulitis of the shoulder (also known as frozen shoulder) is a condition characterised by thickening and contraction of the shoulder joint capsule and surrounding synovium. Adhesive capsulitis can rarely affect other sites such as the ankle 8. Epidemiology The incidence in the genera...
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Adrenal adenoma

Adrenal adenomas are the commonest adrenal mass lesion and are often found incidentally during abdominal imaging for other reasons. In all cases, but especially in the setting of known current or previous malignancy, adrenal adenomas need to be distinguished from adrenal metastases or other adre...
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Adrenal collision tumour

An adrenal collision tumour or collision tumour of the adrenal gland is an uncommon tumour of the adrenal gland, where two histologically distinct tumours abut each other or are in close proximity. Pathology Collision tumours have been reported in nearly every organ, for example collision tumo...
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Adrenal gland trauma

Adrenal gland trauma most commonly results from blunt force trauma. Epidemiology Adrenal gland trauma is present on 1-2% of CT imaging in blunt trauma although the occurrence is thought to be much higher as injury has been demonstrated at 28% in one autopsy series 1-4.  The right adrenal glan...
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Adrenal hyperplasia

Adrenal hyperplasia refers to nonmalignant growth (enlargement) of the adrenal glands and is a rare cause of ACTH-independent Cushing syndrome with unilateral adrenal cortical adenomas being the commonest. 20% of Conn syndrome cases are secondary to adrenal hyperplasia.  In diffuse hyperplasia, ...
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Adrenal lymphangioma

Adrenal lymphangiomas (also known as cystic adrenal lymphangiomas) are rare, benign vascular adrenal lesions. Epidemiology According to one series, there may be a slight right-sided and female predilection 3. Pathology It is supposed to occur as a result of a developmental abnormality of lym...
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Adrenal metastases

Adrenal metastases are the most common malignant lesions involving the adrenal gland. Metastases are usually bilateral but may also be unilateral. When unilateral involvement is thought to be more prevalent on the left side (ratio of 1.5:1). Epidemiology They are thought to be present in up to...
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Adrenal pseudocyst

Adrenal pseudocysts account for approximately 39% 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. Radiographic features Adrenal pseudocysts appear as a ...
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Adrenoleukodystrophy

Adrenoleukodystrophy (ALD) is an X-linked inherited metabolic peroxisomal disorder characterised by 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 in...
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Adventitial bursitis

Adventitial bursitis refers to inflammation associated with adventitious bursae. Adventitious bursae are not permanent bursae and can develop in adulthood at sites where subcutaneous tissue becomes exposed to high pressure and friction, which could then lead to their formation. Clinical presen...
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Adynamic ileus

Adynamic ileus is the failure of passage of enteric contents through small bowel and colon that is not mechanically obstructed. Essentially it represents the paralysis of intestinal motility. Clinical presentation Patients may be asymptomatic or present with symptoms similar to a mechanical bo...
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AFP reduction

Human AFP (alpha-fetoprotein) reduction is seen in pregnancy where it can be associated with:  certain chromosomal anomalies Down syndrome Turner syndrome trisomy 13 trisomy 18 Cornelia de-Lange syndrome 2
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Aggressive angiomyxoma

Aggressive angiomyxomas are rare pelvic 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 predilection for local recurrence. Only rarely does it metastasise.   ...
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Aggressive fibromatosis

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. Terminology The term...
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Aggressive granulomatosis post hip replacement

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. Pathology Aggressive granulomas consist of well organised connective tissue contain...
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AIDS cholangiopathy

AIDS cholangiopathy refers to an acalculous, secondary opportunistic cholangitis that occurs in AIDS patients as result of immunosuppression.  Pathology Characterised by multiple irregular narrowings essentially indistinguishable from primary sclerosing cholangitis (PSC). There are four pathol...
Article

AIDS-related pulmonary lymphoma

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. Pathology ARPL is typically a high-grade B-cell non-Hodgkin's lymphoma and the majority of patients have advanced HIV infection,...
Article

Airway foreign bodies in children

Airway foreign bodies in children are potentially fatal and proper recognition is important because delayed diagnosis is common.  Epidemiology Children under the age of four years are at increased risk of foreign body (FB) aspiration with a slight male predominance 1.  Clinical presentation ...
Article

Airway invasive aspergillosis

Airway invasive aspergillosis refers to a form of invasive aspergillosis.  Epidemiology It usually occurs in immunocompromised neutropenic patients and in patients with AIDS. Aspergillosis affecting the airways as the major or only feature of invasive disease is uncommon and is thought to occu...
Article

Alexander disease

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...
Article

Allergic bronchopulmonary aspergillosis

Allergic bronchopulmonary aspergillosis (ABPA) is at one end of the spectrum of disease caused by pulmonary aspergillosis and can be classified as an eosinophilic lung disease 2-4. Epidemiology This entity is seen is almost only encountered in patients with longstanding asthma, and only occasi...
Article

Allergic fungal sinusitis

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 s...
Article

Alobar holoprosencephaly

Alobar holoprosencephaly is a subtype of holoprosencephaly (HPE), and is the most severe of the classical three subtypes, with both semilobar holoprosencephaly and lobar holoprosencephaly having less severe clinical manifestations. For a general discussion of epidemiology, clinical presentation...
Article

Alpha-1-antitrypsin deficiency

Alpha-1-antitrypsin (AAT) deficiency is a hereditary metabolic disorder. It is the most common metabolic liver disease in children and results in the unopposed action of neutrophil elastase and subsequent severe basal emphysema and respiratory symptoms. Clinical presentation The classic presen...
Article

Alpha-thalassemia/mental retardation syndrome X-linked (ATRX)

Alpha-thalassemia/mental retardation syndrome X-linked (ATRX) has recently been recognised as 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). These two markers are helpful in se...
Article

Alzheimer disease

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.  ...
Article

Ameloblastic fibroma

Ameloblastic fibromas, appear as unilocular lucent mandibular lesions, most frequently in the posterior mandible and are usually associated with impacted teeth, centred on the un-erupted crown. They therefore appear very similar to unilocular ameloblastomas. They are composed of enamel and embry...
Article

Ameloblastoma

Ameloblastomas are benign, locally aggressive tumours that arise from the mandible, or less commonly from the maxilla. Usually presented as a hard painless lesion near the angle of the mandible in the 3rd to 5th decades of life.  On imaging, they are commonly identified as a well-defined, expan...
Article

American Thoracic Society criteria for histopathological diagnosis of usual interstitial pneumonia

American Thoracic Society (ATS) criteria for histopathological diagnosis of usual interstitial pneumonia​ (UIP) are as follows:  advanced subpleural or paraseptal fibrosis +/- honeycombing  patchy temporally heterogeneous fibrosis fibroblastic foci absence of features against UIP inflammato...
Article

Amniotic bands

Amniotic bands refer to free floating blind ending amnion with an intact chorionic membrane. In certain situations they lead to the amniotic band syndrome. They should not be confused with amniotic shelves which refer to the presence of amnion folding around pre-existing uterine adhesions. Some ...
Article

Amoebic colitis

Amoebic colitis is a type of infectious colitis, more common in tropical and subtropical areas. The causative agent is a trophozoite of Entamoeba histolytica. The cyst form may live normally in the colon as commensal. Clinical presentation Amoebic colitis presents with abdominal pain and dysen...
Article

Amoebic hepatic abscess

An amoebic hepatic abscess is a form hepatic abscess resulting from Entamoeba histolytica infection. Clinical presentation Patients may experience general malaise or present with frank sepsis and right upper quadrant pain. Although the causative pathogen is found worldwide, it is endemic to th...

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