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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.

782 results found
Article

Leave alone lesions - maxillodental

Maxillodental leave alone lesions are usually incidental findings that do not require treatment nor follow-up if the patient is asymptomatic. This article includes findings from orthopantomogram, cone-beam CT, and sinus CT studies. Do not touch: benign lesions tooth ankylosis hypercementosi...
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Leave alone lesions - paranasal sinuses

Leave alone lesions are findings that are usually discovered incidentally and do not require any specific treatment or follow-up if the patient is asymptomatic. This article includes findings from paranasal sinus CT and MRI studies. physiological process nasal cycle anatomical variants conc...
Article

Leave alone lesions - skeletal

Skeletal leave alone lesions, also called “do not touch” lesions, are so characteristic radiographically, that further diagnostic tests such as a biopsy are unnecessary and can be frankly misleading and lead to additional unnecessary surgery. Thus a radiologic diagnosis should be made without a ...
Article

Leave alone lesions - skull base

Leave alone lesions of the skull base refers to incidental findings that do not require treatment nor follow-up. This article includes findings from brain CT, HRCT of the temporal bone, and MRI studies. Do not touch: arrested pneumatization of the skull base - sphenoid benign fatty lesion 1 ...
Article

Left paramediastinal catheter position (differential)

When a central venous catheter that is supposed to terminate in the superior vena cava or right atrium is abnormally located to the left of the mediastinum and below the level of the brachiocephalic vein, a limited differential of left paramediastinal catheter position should be considered 1: l...
Article

Leg bowing in children

Leg bowing in children is common and often developmental. Differential diagnosis The differential includes: developmental bowing exaggeration of normal age-related angulation changes at the knee neonates and infants normally have varus angulation that gradually corrects within 6 months of w...
Article

Leptomeningeal enhancement

Leptomeningeal enhancement refers to a diffuse or focal gyriform or serpentine enhancement that can be seen in the following conditions: Diffuse meningitis pyogenic meningitis viral meningitis tuberculous meningitis (can also be focal) CNS cryptococcal infection coccidioidal meningitis (c...
Article

Lesions of the corpus callosum (differential)

Lesions of the corpus callosum are uncommon and arise from multiple different etiologies. The lesions can be classified according to underlying pathophysiology 4-6. Congenital agenesis of the corpus callosum enlarged perivascular spaces tubonodular pericallosal lipoma: associated with dysgen...
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Linear atelectasis

Linear atelectasis (plural: atelectases), and also known as discoid or plate atelectasis refers to a focal area of subsegmental atelectasis that has a linear shape. Linear atelectasis may appear to be horizontal, oblique or perpendicular and is very common. It usually occurs as a consequence of ...
Article

Linitis plastica

Linitis plastica is a descriptive term usually referring to the appearance of the stomach, although the rectum can also be described this way. The appearance is said to be reminiscent of an old leather water-bottle. Pathology The underlying cause is usually a scirrhous adenocarcinoma with diff...
Article

Lobar consolidation

Lobar consolidation is the term used to describe consolidation in one of the lobes of the lung. It infers an alveolar spread of disease and is most commonly due to pneumonia. Pathology Consolidation refers to the alveolar airspaces being filled with fluid (exudate/transudate/blood), cells (inf...
Article

Lobar lung collapse

Lobar collapse refers to the collapse of an entire lobe of the lung. As such it is a subtype of atelectasis (collapse is not entirely synonymous with atelectasis, which is a more generic term for 'incomplete expansion').  Individual lobes of the lung may collapse due to obstruction of the supply...
Article

Localized pulmonary hemorrhage

Localized pulmonary hemorrhage is a descriptive term for a pulmonary hemorrhage restricted to a particular focal region of the lung. It can range from involving a small focus of hemorrhage to a whole lobe. Pathology Etiology Focal pulmonary hemorrhage can occur from a number of causes: pulmo...
Article

Long bone metaphyseal cupping (differential)

Long bone metaphyseal cupping is most likely due to the local oligemia from thrombosis in the terminal epiphyseal arteries to the epiphyseal plate, induced by prolonged regional immobilization 7.  The differential diagnosis of long bone metaphyseal cupping includes:  Common normal variant re...
Article

Longitudinally extensive spinal cord lesion

Longitudinally extensive spinal cord lesions (LESCL), also known as longitudinally extensive transverse myelitis (LETM), represent extensive involvement of the spinal cord, with abnormal T2 signal traversing at least three vertebral body segments in length. Differential diagnosis They are typi...
Article

Loss of intervertebral disc space (differential)

Loss of intervertebral disc space can be due to a variety of causes: degenerative disc disease of the spine: most common cause trauma diskitis neuropathic spondyloarthropathy dialysis related spondyloarthropathy ankylosing spondylitis ochronosis crystal deposition diseases sarcoidosis ...
Article

Lower abdominal/pelvic calcification

Causes of calcifications in the lower abdomen and pelvis include: vascular calcifications atherosclerosis aneurysm phlebolith urogenital uterine fibroid ovarian dermoid prostatic calcification seminal vesicle and ductus deferens calcification bladder stones gallstones dropped stones ...
Article

Lower gastrointestinal bleeding (differential)

Lower gastrointestinal bleeding usually occurs distal to the ligament of Treitz, and has a wide differential diagnosis: diverticular disease enterocolitis infective Crohn’s disease ulcerative colitis ischemic colitis vascular malformation vascular ectasia angiodysplasia arteriovenous m...
Article

Low signal intensity renal parenchyma

There are relatively few causes of low signal intensity renal parenchyma. Causes include: hemolysis paroxysmal nocturnal hemoglobinuria mechanical: malfunctioning prosthetic cardiac valve sickle cell disease infection hemorrhagic fever with renal syndrome (HFRS) vascular disease acute re...
Article

Lytic bone metastases

Lytic bone metastases are due to a variety of primary tumors, and are more common than sclerotic metastases (although many may occasionally have mixed lytic and sclerotic components). They include 1: thyroid cancer renal cell cancer adrenocortical carcinoma and pheochromocytoma endometrial c...
Article

Lytic skull lesion

Lytic skull lesions have a relatively wide differential that can be narrowed, by considering if there are more than one lesion and whether the mandible is involved. Pathology Causes lytic skeletal metastases multiple myeloma epidermoid - scalloped border with a sclerotic rim eosinophilic g...
Article

Macrophthalmia

The increased globe size or macrophthalmia may have many differentials: buphthalmos (congenital glaucoma) axial myopia macrophthalmus in neurofibromatosis type 1 (NF1) connective tissue disorders: Marfan syndrome, Ehlers-Danlos syndrome Focal enlargement: staphyloma coloboma See also mi...
Article

Main differentials in musculoskeletal imaging

Here is a list of some of the most useful differential diagnoses in musculoskeletal imaging. By process lucent/lytic bone lesions (FEGNOMASHIC) multiple lucent/lytic bone lesions benign lytic bone lesions in patients under 30 years old diffuse bony sclerosis permeative process in bone pse...
Article

Malignant neoplasms involving the uterus

Malignant neoplasms involving the uterus account for a significant proportion of all female cancers. They can be classified as: endometrial carcinoma : commonest: >90% of all uterine malignancies endometrioid carcinoma of the uterus: commonest histological type, ~80% papillary serous carcino...
Article

Malignant esophageal neoplasms

Malignant esophageal neoplasms are much more common than benign esophageal neoplasms, especially if the patient is symptomatic.  Pathology esophageal carcinoma (90%) esophageal squamous cell carcinoma (SCC) esophageal spindle cell carcinoma esophageal adenocarcinoma esophageal neuroendocri...
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Malignant vs benign gastric ulcer (barium)

Barium meal has been frequently used to differentiate malignant and benign gastric ulcers: Features suggesting benign gastric ulcer outpouching of ulcer crater beyond the gastric contour (exoluminal) smooth rounded and deep ulcer crater smooth ulcer mound smooth gastric folds that reach the...
Article

Mandibular lesions

Mandibular lesions are myriad and common. The presence of teeth results in lesions that are specific to the mandible (and maxilla) and a useful classification that defines them as odontogenic or non-odontogenic. While it may often not be possible to make a diagnosis on imaging alone, this classi...
Article

Mandibular periostitis

There are many causes for mandibular periostitis: Langerhans cell histiocytosis malignancy (both primary and metastatic) necrosis, e.g. radiation osteonecrosis osteomyelitis pyogenic Garre's sclerosing osteomyelitis actinomycosis (uncommon) syphilis (uncommon) tuberculosis (uncommon) r...
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Masses arising from the foramen of Monro (differential)

The differential diagnosis of masses arising from the foramen of Monro can be approached depending on the age of the patient. Pediatric choroid plexus papilloma craniopharyngioma germinoma glioma Langerhans cell histiocytosis neurofibromatosis pilocytic astrocytoma subependymal giant ce...
Article

Mass-forming chronic pancreatitis

Mass-forming chronic pancreatitis occurs in around 30% of cases of chronic pancreatitis, where a mass or a focal enlargement of the pancreas is usually seen on imaging. In many instances, it poses a challenge as the epidemiology and imaging appearances overlap those of pancreatic adenocarcinoma....
Article

Mastoid air cell opacification

Mastoid air cell opacification can occur in a number of situations and can include a spectrum of inflammatory, neoplastic, vascular, fibro-osseous, and traumatic changes. Possible causes include: otomastoiditis acute otomastoiditis chronic otomastoiditis radiation 3 trauma (temporal bone f...
Article

Maurice Reeder

Maurice "Mo" M Reeder (1933-2013) was an American radiologist who is remembered for his contributions to radiology education in the United States, in particular, the development of the radiology-pathology teaching program at the Armed Forces Institute of Pathology. Early life Maurice Merrick R...
Article

Meckel cave lesions (differential)

Meckel cave lesions are numerous. The aim of this article is to list them in an easy way for revision and assessment of differential diagnosis.  Neoplastic Meckel cave tumors account for only 0.5% of all intracranial tumors. The most common histologies are: trigeminal schwannoma: most common,...
Article

Mediastinal lymph node enlargement

Mediastinal lymph node enlargement can occur from a wide range of pathologies, either by its own or in association with other lung pathology. Historically, a size cut-off of 10 mm short-axis diameter was used.  Terminology Although mediastinal lymphadenopathy is used interchangeably - by some ...
Article

Mediastinal widening (differential)

The differential diagnoses for mediastinal widening include: traumatic aortic injury vascular anomalies unfolded aorta thoracic aortic aneurysm double SVC aberrant right subclavian artery azygos continuation of the IVC pneumomediastinum lung atelectasis pulmonary masses abutting the m...
Article

Medical devices in the abdomen and pelvis

Medical devices in the abdomen and pelvis are important to be recognized, just like medical devices of the chest. Often we ignore these devices, considering them to be incidental and non-pathological, however it is essential to be aware of potential complications. Gastrointestinal tubes stomac...
Article

Medical devices in the head and neck

Medical devices in the head and neck are regularly observed by radiologists on plain film, CT and MRI reporting. They include devices which pass through the neck into the chest and stomach or ascend to/into the head. Vascular access devices dialysis catheters peripherally inserted central cat...
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Medical devices in the thorax

Medical devices in the thorax are regularly observed by radiologists when reviewing radiographs and CTs. Extrathoracic devices tubing, clamps, syringes, scissors, lying on or under the patient rubber sheets, foam mattresses, clothing, hair braids, nipple piercings, etc. may also be visible T...
Article

Medullary nephrocalcinosis

Renal medullary nephrocalcinosis is the commonest form of nephrocalcinosis and refers to the deposition of calcium salts in the medulla of the kidney. Due to the concentrating effects of the loops of Henle, and the biochemical milieu of the medulla, compared to the cortex, it is 20 times more co...
Article

Megaesophagus

Megaesophagus or diffuse esophageal dilatation can be caused by a variety of conditions.  Pathology Etiology Some of the more common causes are given below 1-3: esophageal dysmotility achalasia Chagas disease scleroderma distal obstruction malignant stricture, e.g. esophageal cancer, ca...
Article

Meningeal enhancement

Meningeal enhancement is a generic term related to the enhancement of the membranes that envelop the brain and spinal cord. Due the anatomical features, this enhancement can be divided in two subtypes: leptomeningeal enhancement (pial or pial-arachnoid enhancement) dural (pachymeningeal) enhan...
Article

Metal-on-metal pseudotumor

Metal-on-metal pseudotumors represent mass-forming inflammation around a metal-on-metal hip or knee replacement. The term describes one presentation on the spectrum of adverse reaction to metal debris. Clinical presentation Metal-on-metal pseudotumors are large focal solid or semiliquid masses...
Article

Metaphyseal blanch sign

The metaphyseal blanch sign (or metaphyseal blanch sign of Steel) is one of the signs seen on AP views of the adolescent hip indicating posterior displacement of the capital epiphysis. It is a crescent-shaped area of increased density, that overlies the metaphysis adjacent to the physis on the ...
Article

Metaphyseal lesions

The differential diagnosis for metaphyseal lesions includes: osteomyelitis metastases non-ossifying fibroma enchondroma aneurysmal bone cyst simple bone cyst chondromyxoid fibroma chondrosarcoma cortical desmoid giant cell tumor desmoplastic fibroma intraosseous lipoma osteosarcoma ...
Article

Middle ear tumors

There are a range of middle ear tumors, which are more likely to be benign than malignant.  Pathology The three most common middle ear tumors are (not in any particular order as there are differences in the literature) 1-3:  glomus tympanicum paraganglioma congenital cholesteatoma middle ea...
Article

Middle mediastinal mass

The differential diagnosis for a middle mediastinal mass includes 1-3: lymphadenopathy aneurysm e.g. aortic, pulmonary artery, bronchial artery congenital cyst pericardial cyst foregut duplication cyst (e.g. esophageal, bronchial) pericardial tumor primary/secondary cardiac tumor neuroge...
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Midline neck mass

Midline neck masses have a relatively narrow differential, as few structures are present in the midline. Dividing the causes according to structure of origin is a useful schema. lymph node(s): Delphian node(s) inflammatory adenopathy malignancy thyroid gland thyroglossal duct cyst thyroid ...
Article

Midline shift

One of the most important indicators of increased intracranial pressure due to mass effect is midline shift. Pathology Any intra-axial or extra-axial lesion (tumor, hemorrhage, abscess, etc.) has the potential to exert mass effect on the brain parenchyma and cause lateral shift of the midline ...
Article

Miliary opacities (lungs)

The term miliary opacities refers to innumerable, small 1-4 mm pulmonary nodules scattered throughout the lungs. It is useful to divide these patients into those who are febrile and those who are not. Additionally, some miliary opacities are very dense, narrowing the differential - see multiple...
Article

Milk of calcium within a breast cyst

Milk of calcium within a breast cyst is a mammographic feature observed when there is dependent calcium layering within breast cysts. It is typically observed as "tea cup" or "crescent shaped" calcifications on a true lateral (LM or ML) view on occasionally on a MLO view. On a CC view, these cal...
Article

Mixed cystic and solid pituitary region mass

A mixed cystic and solid pituitary region mass has a limited differential. Differential diagnosis craniopharyngioma both papillary (more solid) and adamantinomatous (more cystic) macroadenoma cystic change / necrosis / previous hemorrhage Most other solid and enhancing pituitary region mas...
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Mixed lytic and sclerotic bone metastases

Mixed lytic and sclerotic bone metastases are seen in a number of malignancies: breast carcinoma: typically sclerotic but 25% are mixed lung carcinoma: typically lytic but 15% are mixed carcinoma of the cervix testicular tumors prostate carcinoma: typically sclerotic but 15% are mixed  gan...
Article

Monoarthritis (differential)

Monoarthritidies have a relatively short differential diagnosis, including: Common septic arthritis osteoarthritis (post-traumatic) gout Charcot joint  (neuropathic joint) pigmented villonodular synovitis (PVNS) synovial osteochondromatosis Less common hemophilia tuberculosis fungal ...
Article

Monoarticular arthropathy

Monoarticular arthropathy can result from a number of causes: Commonest 2: gout (15-27%) septic arthritis (8-27%) osteoarthritis (5-17%) rheumatoid arthritis (RA) (11-16%) Less common 2: traumatic arthritis HADD (hydroxyapatite deposition disease) reactive arthritis 2 avascular necrosi...
Article

Mosaic attenuation pattern in lung

Mosaic attenuation is a descriptive term used in describing a patchwork of regions of differing pulmonary attenuation on CT imaging. It is a non-specific finding, although is associated with the following: obstructive small airways disease: low attenuation regions are abnormal and reflect two p...
Article

Mostly/purely cystic pituitary region masses

Mostly/purely cystic pituitary region masses have a short differential. Differential diagnosis Rathke cleft cyst arachnoid cyst empty sella craniopharyngioma (adamantinomatous type): 90% have calcification  epidermoid cyst
Article

Moyamoya syndrome

Moyamoya syndrome, also termed the moyamoya pattern or phenomenon, is due to numerous conditions that can cause arterial occlusion of the circle of Willis, with resultant collaterals, and appearances reminiscent of moyamoya disease. These conditions include 1-4 : vessel wall abnormalities athe...
Article

Mucoid impaction (lung)

Mucoid impaction, also referred to as mucus plugging, mucous plugging, bronchial mucocele or bronchocele formation, refers to airway filling by mucoid secretions and can be obstructive or non-obstructive. It is a common pathological finding in chest imaging. Pathology Etiology Mucoid impactio...
Article

Multicentric breast cancer

A multicentric breast cancer is a term given to a breast cancer where there are two or more breast cancers separated by normal breast tissue (often taken as 5 cm of separation 4). It is related to but distinct from the term multifocal breast cancer. At a pathological level It can also mean 2 t...
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Multifocal breast cancer

Multifocal breast cancer refers to two or more individual breast cancers diagnosed at the same time within the same quadrant of the same breast 1. 
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Multilayered periosteal reaction

Multilayered periosteal reaction, also known as a lamellated or onion skin periosteal reaction, demonstrates multiple concentric parallel layers of new bone adjacent to the cortex, reminiscent of the layers on an onion. The layers are thought to be the result of periods of variable growth 2 and ...
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Multiple cranial nerve thickening and enhancement

The most common causes of multiple cranial nerve thickening and enhancement include: metastasis (most common) neurofibromatosis type II lymphoma and leukemia  multiple sclerosis chronic inflammatory demyelinating polyneuropathy Lyme disease  See also cranial nerve enhancement: for comple...
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Multiple cystic neck lesions (differential)

The differential diagnosis for multiple cystic neck lesions is different to that for a solitary cystic neck mass. Differential diagnosis Cystic neck lesions are seen in: metastatic squamous cell carcinoma: older patient, M>F metastatic papillary thyroid carcinoma: usually a younger patient, ...
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Multiple filling defects of the ureter (differential)

Multiple filling defects within a ureter, as seen on conventional IVU or CT IVU, have a relatively small differential including: spreading or multifocal transitional cell carcinoma (TCC) vascular indentations multiple ureteral stones (steinstrasse) blood clots ureteritis cystica Stevens-Jo...
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Multiple intracranial calcifications

Intracranial calcifications are common in certain locations and often are of no clinical concern. The two most commonly encountered types of calcification include:  normal age-related intracranial calcifications intracranial arterial atherosclerosis Concerning calcifications are much less co...
Article

Myocardial edema

Myocardial edema refers to an increased water content of the myocardium particularly within the extracellular interstitium 1. Clinical presentation Myocardial edema often reflects an acute or subacute cardiac event, most often either ischemic or inflammatory and thus can be associated with che...
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Myonecrosis

Myonecrosis is a myopathy involving infarction of skeletal muscle and can have the appearances of an intramuscular mass.  Pathology Myonecrosis represents an infarction of the skeletal muscles. It has a variety of causes 1,2,3: post-traumatic (see: calcific myonecrosis) - most common compart...
Article

Narrow fetal thorax

A narrow fetal thorax on antenatal ultrasound can be present with a number of anomalies which include: achondrogenesis campomelic dysplasia homozygous achondroplasia Jarcho-Levin syndrome Jeune syndrome - asphyxiating thoracic dysplasia Russell-Silver dwarfism short rib polydactyly syndro...
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Narrowing of interpedicular distance

The interpedicular distance is the measurement between the pedicles on frontal/coronal imaging, which can be narrowed in a number of situations. Causes include achondroplasia 3 thanatophoric dysplasia 2 See also  widening of interpedicular distance See reference 1 for an old but interesti...
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Neonatal respiratory distress (causes)

Causes of neonatal distress can be broadly split into intrathoracic, extrathoracic and systemic: Intrathoracic Medical respiratory distress syndrome (RDS) transient tachypnea of the newborn (TTN) meconium aspiration syndrome bronchopulmonary dysplasia (BPD) patent ductus arteriosus (PDA) ...
Article

Neoplasms of the cauda equina (differential)

The differential diagnosis for masses of the cauda equina region is often considered separately to the remainder of the spinal cord. It is often difficult to determine whether masses in this region are intramedullary or intradural-extramedullary. Most common tumors myxopapillary ependymoma by...
Article

Nephrocalcinosis

Nephrocalcinosis, previous known as Anderson-Carr kidney or Albright calcinosis, refers to the deposition of calcium salts in the parenchyma of the kidney. It is divided into several types, with differing etiologies, based on the distribution: medullary nephrocalcinosis: 95% cortical nephrocal...
Article

Nerve root enhancement

Nerve root enhancement is phenomenon described on post contrast MRI scans that can be observed in a number of situations. Common causes post-operative states post-operative nerve root enhancement arachnoiditis leptomeningeal metastases disseminated spinal leptomeningeal metastases neuroly...
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Nodular filling defects of duodenum (differential)

Nodular filling defects due to mucosal lesions in the duodenum are due to a number of processes. For a differential list which includes non-mucosal lesions see duodenal filling defects. The differential diagnosis for mucosal lesions includes:  heterotopic gastric mucosa 1-2 mm clustered onl...
Article

Nodular pleural thickening

Nodular pleural thickening is a form of pleural thickening. Pathology Etiology Most common causes of nodular pleural thickening are malignant and include: metastatic pleural disease, particularly from adenocarcinomas, e.g. bronchogenic adenocarcinoma breast cancer ovarian cancer prostate...
Article

Non-calcified hyperdense pulmonary nodules

Non-calcified hyperdense pulmonary nodules are predominantly the result of inhalational exposure to substances, although embolization of material may cause dense nodular opacification within the lung. inhalation disease, e.g. pneumoconioses pulmonary baritosis (barium dust) pulmonary siderosi...
Article

Non-cardiogenic pulmonary edema

Non-cardiogenic pulmonary edema is a classification of pulmonary edema where the underlying etiology is not due to left ventricular dysfunction. Causes include: fluid overload pulmonary edema with acute asthma post-obstructive pulmonary edema/postintubation pulmonary edema/negative pressure ...
Article

Non-neoplastic solid lesions of the pancreas

Non-neoplastic solid lesions of the pancreas are conditions which may mimic pancreatic neoplasms on imaging. They include: focal pancreatitis autoimmune pancreatitis fatty infiltration-replacement intrapancreatic accessory spleen peripancreatic lymph node congenital anomalies prominent pa...
Article

Obstruction of nasolacrimal drainage apparatus

Obstruction of nasolacrimal drainage apparatus results in epiphora and can be primary or secondary, congenital or acquired. Obstruction can occur at canalicular, lacrimal saccular, or nasolacrimal ductal (post-saccular) levels. Causes of obstruction Congenital obstruction persistence of the m...
Article

Obstructive uropathy

An obstructive uropathy is a catch-all term encompassing any cause of complete or partial, congenital or acquired, and permanent or intermittent obstruction of the urinary tract. Depending on the severity of obstruction and extent, it may result in permanent change in both the collecting system ...
Article

Ocular metastasis

Ocular metastases, also termed uveal metastases, account for over 80% of all ocular pathology, and need to be distinguished from extraocular metastasis, which are a quite different group of tumors. This article will discuss metastatic lesions affecting the orbits. For other intracranial metasta...
Article

Ocular pathology

Ocular pathology covers a wide range of conditions and therefore represents the cause of a wide range of symptoms, signs and radiographic features. Ocular metastases account for over 80% of all ocular pathology. With regard to the remainder of ocular lesions, the primary differentiating factor ...
Article

Esophageal wall thickening

Esophageal wall thickening can be observed in a number of situations and can be either focal or diffuse. It may be physiological, and can also be due to benign or malignant disorders. Pathology Causes diffuse diffuse esophageal spasm forms of esophagitis diffuse esophageal intramural hemat...
Article

Oligohydramnios

Oligohydramnios refers to a situation where the amniotic fluid volume is less than expected for gestational age. Often these fetuses have <500 mL of amniotic fluid. Epidemiology The estimated prevalence can be up to ~6% of pregnancies 4. Pathology Causes The causes of oligohydramnios are pr...
Article

Omental cake

Omental cake refers to infiltration of the omental fat by material of soft-tissue density. The appearances refer to the contiguous omental mass simulating the top of a cake. Masses on the peritoneal surfaces and malignant ascites may also be present.  Pathology The most common cause is metasta...
Article

Ophthalmoplegia

Ophthalmoplegia describes the abnormal eye movement that occurs because of paralysis of one or more of the six extraocular muscles involved in eye movements. Classification can be based on the cause of the ophthalmoplegia or the directions of the affected movements. There are numerous causes of...
Article

Optic canal enlargement

Optic canal enlargement can be caused by numerous etiologies. Pathology The optic canal has an average transverse diameter of 3.6 ± 0.6 mm 1. The optic canal can be considered enlarged when it is >6.5 mm in transverse diameter 4. Etiology glioma of optic nerve meningioma of optic nerve shea...
Article

Optic nerve enlargement

Enlargement of the optic nerves is uncommon and has a surprisingly broad differential. Etiology nepolastic optic nerve glioma optic nerve meningioma leukemia orbital lymphoma metastases juvenile xanthogranuloma medulloepithelioma involvement by retinoblastoma cyst of optic nerve sheat...
Article

Orbital cystic lesions

Several cystic and cyst-like orbital lesions may be encountered in imaging of the orbits: developmental orbital cysts choristoma dermoid: commonest benign orbital tumor in childhood  epidermoid teratoma  congenital cystic eye colobomatous cyst acquired abscess hematoma lacrimal gland ...
Article

Orbital mass

An orbital mass carries a relatively wide differential: tumors lymphoma metastasis lacrimal gland or duct tumors rhabdomyosarcoma of the orbit retinoblastoma optic nerve meningioma optic nerve glioma schwannoma (of trigeminal or other cranial nerves except optic) neurofibroma developm...
Article

Orbital vascular lesions

Orbital vascular lesions may be difficult to distinguish on imaging. However, the following conditions have been described: arteriovenous malformation (AVM) capillary hemangioma cavernous hemangioma orbital lymphangioma / lymphangiovenous malformation / venolymphatic malformation orbital ve...
Article

Osteoporosis (differential)

The differential for osteoporosis includes: idiopathic  endocrine hypogonadism ovarian postmenopausal testicular eunuchoidism Cushing syndrome diabetes mellitus acromegaly Addison disease hyperthyroidism mastocytosis (mast cells produce heparin) pseudohypoparathyroidism pseudopseu...
Article

Ovarian lesions with T2 hypointensity

A hypointense ovarian lesion on T2 weighted MRI is usually a sign of benignity.  The low signal is considered to be due to fibrosis and blood products 1. Lesions that can give this appearance include 1: endometrioma Brenner tumor ovarian fibroma ovarian fibrothecoma ovarian cystadenofibrom...

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