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Enlarged posterior fossa 'CSF' space

An enlarged posterior fossa 'CSF' space posterior to the cerebellum has a number of differentials that include: mega cisterna magna epidermoid cyst arachnoid cyst Careful attention to the cerebellum needs to paid as also to be considered are: cerebellar atrophy Dandy-Walker malformations ...

White matter changes in HIV

White matter changes in HIV have overlapping appearances and varied in etiology. These can be divided into: primary effects of HIV opportunistic infection neoplasms vascular disease metabolic and nutritional disorders Primary effects of HIV HIV encephalitis Opportunistic infection cyto...

Intraventricular neoplasms and lesions

Intraventricular neoplasms are rare and arise from periventricular structures such as the walls of the ventricular system, the septum pellucidum and the choroid plexus. Many tumor types arise from or can bulge into the ventricular system, although there are certain lesions that are relatively re...

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...

Hyperreninaemic hypertension (differential)

Hyperreninaemic hypertension may have many causes including: renal artery stenosis renal secreting tumor, e.g. renal cell carcinoma, reninoma renal compression: large renal mass, subcapsular hemorrhage (Page kidney)

Renal artery stenosis

Renal artery stenosis (RAS) (plural: stenoses) refers to a narrowing of a renal artery. When the process occurs slowly, it leads to secondary hypertension. Acute renal artery stenosis does not lead to hypersecretion of renin. Pathology When the stenosis occurs slowly, collateral vessels form a...

Thoracic aortic stenosis (differential)

The differential for thoracic aortic stenosis includes: atherosclerosis aortitis (especially Takayasu arteritis) radiotherapy coarctation pseudocoarctation Williams syndrome: supravalvular aortic stenosis congenital rubella syndrome: supravalvular aortic stenosis

Thoracic aortic dilatation (differential)

There is a broad differential for thoracic aortic dilatation. Differential diagnosis senile ectasia hypertension post-stenotic dilatation, e.g. bicuspid aortic valve thoracic aortic aneurysm atherosclerosis (usually descending thoracic aorta) collagen disorders Marfa...

Hypothalamic lesions

Hypothalamic lesions are numerous representing some entities that are unique to the hypothalamus, as well as many lesions that can be seen elsewhere within the brain. Additionally, due to its proximity to the optic chiasm, third ventricle and pituitary region, many lesions of these locations can...

Vertebral scalloping

Vertebral scalloping is a concavity to the posterior (or less commonly anterior) aspect of the vertebral body when viewed in a lateral projection. A small amount of concavity is normal, as is concavity of the anterior vertebral body (see vertebral body squaring). Posterior scalloping Causes of...

Upper lobe bronchiectasis

Distribution of bronchiectasis can help in narrowing the differential diagnosis. Upper lobe bronchiectasis is typically seen in: cystic fibrosis tuberculosis Rarely it may be seen with non-tuberculous mycobacterial infection (e.g. MAC infection 2). Traction bronchiectasis in the upper lobes c...

Unilateral facet dislocation

Unilateral facet dislocation is a relatively stable type of facet dislocation. Pathology Mechanism Flexion/distraction associated with rotation. The inferior articular facet of vertebral above moves over the superior facet of the vertebral below and becomes locked. It usually affects C4-C5 or...

Tracheal masses

The differential for tracheal masses can be rather wide. For a single mass consider: metastasis direct invasion from adjacent organ (lung, thyroid, esophagus and larynx) distant metastasis (e.g. melanoma, breast, renal, and colon cancer) primary neoplasms squamous cell carcinoma: commone...

Differential diagnoses for temporal lobe tumors

Most tumors of the CNS can potentially occur in the temporal lobe, but entities with a predilection for being diagnosed in this location include: pleomorphic xanthoastrocytoma (PXA) ganglioglioma pilocytic astrocytoma dysembryoplastic neuroepithelial tumor (DNET) multinodular and vacuolatin...

Pituitary region masses

A simple and popular mnemonic to remember the common suprasellar/parasellar/intrasellar masses is SATCHMO. The more comprehensive list includes: tumors pituitary adenoma (commonest in the adult population) pituitary macroadenoma pituitary microadenoma pituitary carcinoma pituitary lymphoma...

Superscan

A superscan is an imaging appearance on a Tc-99m diphosphonate bone scan which occurs as a result of a high ratio of bone to soft tissue tracer accumulation. Intense osteoblastic activity in the bones causes diminished renal and background soft tissue uptake. Pathology Etiology This appearanc...

Splenic cyst

Splenic epithelial cysts, also known as splenic epidermoid cysts or primary splenic cysts, are unilocular fluid lesions with thin and smooth walls and no enhancement. They represent ~20% of cysts found in the spleen, and are usually an innocuous incidental imaging finding. Note that most (~80%)...

Spinal epidural mass

The differential diagnosis for a spinal epidural mass includes: epidural metastasis epidural abscess herniated nucleus pulposus epidural hematoma epidural arteriovenous malformation epidural angiolipoma epidural lipomatosis extramedullary hematopoiesis spinal schwannoma spinal meningio...

Spiculated periosteal reaction

Spiculated periosteal reaction represents spicules of new bone-forming along vascular channels and the fibrous bands that anchor tendons to bone (Sharpey fibers). Pathology A spiculated periosteal reaction signifies a rapid underlying process that prevents the formation of new bone under the r...

Solid periosteal reaction

Solid periosteal pattern is thought to evolve from single layer and multilayered periosteal reactions, forming a solid layer of mature new bone adjacent to the cortex. It denotes a longstanding pathological process. Differential diagnosis osteoid osteoma osteomyelitis osteosarcoma chondrosa...

Small bowel fold thickening (differential)

The differential diagnosis of small bowel fold thickening is broad. Diffuse fold thickening may be "regular and smooth" or "irregular and nodular". Regular, smooth generalized thickening edema congestive cardiac failure (CCF) hypoalbuminemia lymphatic obstruction angioneurotic edema infec...

Single layer periosteal reaction

Single layer (or lamellar) periosteal reaction is a uniformly dense, single thin layer of new bone about 1-2 mm from the cortical surface. It usually denotes an acute or subacute pathological process. Passive hyperemia causes increased osteoblastic activity and production of new bone. Pathology...

Shortening of the fourth/fifth metacarpals

Shortening of the fourth/fifth metacarpals (brachymetacarpia) and less commonly metatarsals (brachymetatarsia) is seen in a variety of apparently disparate conditions. Pathology Etiology Common causes 2: idiopathic post-infective (e.g. osteomyelitis, yaws, tuberculosis dactylitis) pseudoh...

Glenohumeral instability

Glenohumeral instability is the tendency of the glenohumeral joint to sublux or dislocate due to loss of its normal functional or anatomical stabilizers. Clinical presentation Glenohumeral instability can be divided into: static lack of alignment at rest position, which can be depicted using...

Salivary gland tumors

Salivary gland tumors are variable in location, origin, and malignant potential. Pathology In general, the ratio of benign to malignant tumors is proportional to the gland size; i.e. the parotid gland tends to have benign neoplasms, the submandibular gland 50:50, and the sublingual glands and...

Reverse bat wing pulmonary opacities

Reverse bat wing pulmonary opacities refer to peripheral opacities of the lungs, sparing the perihilar region. It is a relatively unusual appearance with a fairly narrow differential 1: chronic eosinophilic pneumonia organizing pneumonia (formerly bronchiolitis obliterans with organizing pneum...

Pyometrium

Pyometrium refers to infection of the endometrial cavity with resulting expansion due to accumulated pus (pyometra). The postmenopausal demographic are most commonly affected due to the association with uterine malignancy. Pathology Etiology endometritis / pelvic inflammatory disease uterin...

Periosteal reaction

Periosteal reaction is a nonspecific radiographic finding that indicates new bone formation in reaction to the abnormal stimulants. Periosteal reactions may be broadly characterized as benign or aggressive, or more specifically categorized by pattern. Terminology Periosteal reaction is the rec...

Peritoneal calcification

Peritoneal calcification is seen in a limited number of conditions that result in calcification of peritoneal structures. Therefore, the differential diagnosis is small: psammoma bodies in malignancy (most frequently cystadenocarcinoma of the ovary): fine sand-like calcification pseudomyxoma p...

Pear-shaped bladder

Pear-shaped (or teardrop-shaped) bladder is one whose normal round or ovoid shape has been extrinsically compressed to resemble a pear. The pear may be inverted or upright, depending on how the excess pelvic tissue compresses the bladder. Pathology Etiology Causes of a pear-shaped bladder inc...

Pancreatic neoplasms

There are numerous primary pancreatic neoplasms, in part due to the mixed endocrine and exocrine components. Classification Classification based on function exocrine: ~99% of all primary pancreatic neoplasms pancreatic ductal adenocarcinoma (commonly known as pancreatic cancer) 90-95% acin...

Pediatric renal tumors and masses

Pediatric renal tumors and masses are another group of diseases (just like cystic renal diseases in both the adult and child) that are bewildering in their number, nomenclature and overlapping findings. Commoner lesions Wilms tumor: common in older children 1-8 years old nephroblastomatosis: ...

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...

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...

Nephrocalcinosis

Nephrocalcinosis, previously 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 nephroc...

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 ...

Twin pregnancy

Twin pregnancies are the most common multifetal pregnancies. Epidemiology Multifetal pregnancies account for ~1% of all pregnancies but are seen in much higher numbers in populations where in vitro fertilisation (IVF) is a common practice. Classification A twin pregnancy can be broadly cate...

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...

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...

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...

Intracranial hemorrhage

Intracranial hemorrhage (ICH) is a collective term encompassing many different conditions characterized by the extravascular accumulation of blood within different intracranial spaces. A simple categorization is based on location: intra-axial hemorrhage intracerebral hemorrhage basal ganglia ...

Intervertebral disc calcification

Intervertebral disc calcification is a non-specific finding seen in numerous conditions. Epidemiology It may be observed in pediatric 5 as well as adult populations. Pathology Etiology degenerative: relatively common and may occur in up to 6% of routine abdominal radiographs in adults post...

Idiopathic interstitial pneumonias

The idiopathic interstitial pneumonias (IIPs) are diffuse interstitial lung diseases of unknown cause. They are characterized by cellular infiltration of the interstitial compartment of the lung with varying degrees of inflammation and fibrosis. Classification Over the years many attempts have...

Hypervascular liver lesions

Hypervascular liver lesions are findings that enhance more or similarly to the background hepatic parenchyma in the late arterial phase, on contrast-enhanced CT or MRI. Differential diagnosis Non-neoplastic vascular shunts intrahepatic arterioportal shunt intrahepatic arteriovenous shunt f...

Hyperostosis of the skull (differential)

Hyperostosis of the skull has many causes, broadly divided into focal or diffuse. Diffuse Paget disease of bone metastatic disease, especially prostate carcinoma chronic, severe anemia hyperparathyroidism acromegaly osteopetrosis hyperostosis frontalis interna long-term phenytoin use g...

Hemithorax white-out (differential)

Complete white-out of a hemithorax on the chest x-ray has a limited number of causes. The differential diagnosis can be shortened further with one simple observation: the position of the trachea. Is it central, pulled or pushed from the side of opacification? Is there pulmonary volume loss or vo...

Hemorrhagic intracranial metastases

Hemorrhagic intracranial metastases are considered to represent between 3-14% of all cerebral metastases (cf. 1-3% of gliomas are hemorrhagic). These classically originate from: melanoma renal cell carcinoma choriocarcinoma thyroid carcinoma: papillary carcinoma of the thyroid has the highe...

Ground-glass opacification

Ground-glass opacification/opacity (GGO) is a descriptive term referring to an area of increased attenuation in the lung on computed tomography (CT) with preserved bronchial and vascular markings. It is a non-specific sign with a wide etiology including infection, chronic interstitial disease an...

Gas in the urinary bladder

There are numerous causes of gas in the urinary bladder. In the hospital setting by far the most common is the recent placement of an indwelling urinary catheter. Other causes include 1: iatrogenic indwelling urinary catheter is by far the most common cause cystoscopy, etc. ...

Erlenmeyer flask deformity

Erlenmeyer flask deformity (EFD), also known as metaphyseal flaring, refers to a radiographic appearance typically on a femoral radiograph demonstrating relatively reduced constriction of the diaphysis and flaring of the metaphysis as a result of undertubulation. The name refers to the resembl...

Endobronchial metastases

Endobronchial metastases are an uncommon form of intrathoracic metastases. They are much less common than intrapulmonary metastases. Clinical presentation The clinical presentation varies and includes: hemoptysis cough post-obstructive pneumonitis from distal obstruction Pathology Frequen...

Empty gestational sac

Empty gestational sacs can be due to a number of causes: anembryonic pregnancy (also known as "blighted ovum") early pregnancy (intrauterine): by 5.5 weeks gestational age, a yolk sac should be identifiable by transvaginal ultrasound pseudogestational sac with an ectopic pregnancy gestationa...

Elevated hemidiaphragm

An elevated hemidiaphragm may result from direct and indirect causes which include: above the diaphragm 1 decreased lung volume atelectasis/collapse prior lobectomy or pneumonectomy pulmonary hypoplasia pulmonary fibrosis diaphragm 3-7 phrenic nerve palsy cervical myelopathy neuromuscu...

Disorganized periosteal reaction

Disorganized or complex periosteal reaction has spicules with random orientation and appearance. It is often seen in highly aggressive processes. Pathology It has been associated with: osteosarcoma metastasis osteomyelitis chondrosarcoma Ewing sarcoma stress fracture malignant fibrous h...

Distal clavicular erosion (differential)

Erosion or absence of the distal ends of the clavicles may be seen in a wide range of conditions. Differential diagnosis Bilateral erosions atraumatic distal clavicular osteolysis: due to repetitive microtrauma; classically described in weightlifters, but can affect anyone performing repetiti...

Discrete colonic ulceration

Discrete colonic ulcerations are nonspecific findings, and can be due to: Crohn disease infective colitis Yersinia entercolitis shigellosis tuberculosis cytomegalovirus (CMV) amoebic colitis vasculitic colitis Behcet disease

Erosion of the odontoid process (differential)

Erosion of the odontoid peg can result from a number of pathological entities: inflammatory arthropathy rheumatoid arthritis: classic 1,2 systemic lupus erythematosus crystal arthropathy calcium pyrophosphate arthropathy (CPPD): relatively common gout non-inflammatory arthropathy: osteoar...

Cystic parotid lesions

The differential for cystic parotid lesions includes: bilateral cystic parotid lesions Warthin tumor benign lymphoepithelial lesions of HIV Sjögren syndrome sialoceles dysgenetic polycystic disease of salivary glands unilateral cystic parotid lesion(s) Warthin tumor sialocele first bra...

Cystic (necrotic) lymph nodes

Cystic or necrotic appearing lymph nodes can be caused by a number of infectious, inflammatory or malignant conditions: Systemic squamous cell carcinoma metastases treated lymphoma leukemia plasmacytoid T-cell leukemia acute myeloid leukemia viral lymphadenitis herpes simplex lymphadenit...

Cystic lesions of the pancreas (differential)

The differential for cystic lesions of the pancreas includes: unilocular pancreatic pseudocyst intraductal papillary mucinous neoplasm (IPMN) serous cystadenoma uncommonly uni/macrolocular simple pancreatic cyst cystic neuroendocrine tumor of the pancreas diffuse pancreatic cysts pancrea...

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, ...

Cystic mediastinal masses

The differential diagnosis for cystic masses of the mediastinum include: foregut duplication cysts bronchogenic cyst esophageal duplication cyst neuroenteric cyst pericardial cyst meningocele lymphangioma thymic cyst cystic teratoma of mediastinum cystic degeneration of an intrathoraci...

Crazy paving

Crazy paving refers to the appearance of ground-glass opacities with superimposed interlobular septal thickening and intralobular septal thickening, seen on chest HRCT or standard CT chest. It is a non-specific finding that can be seen in a number of conditions. Pathology Etiology Common cau...

Colonic stricture

Colonic strictures can be long (>10 cm) or short. Short scirrhous colorectal carcinoma (apple core sign) post surgical (anastamotic stricture) Long malignancy scirrhous colorectal carcinoma gastrointestinal lymphoma inflammatory bowel disease ulcerative colitis Crohn disease post radi...

Codman triangle periosteal reaction

A Codman triangle is a type of periosteal reaction seen with aggressive bone lesions. The periosteum does not have time to ossify with shells of new bone (e.g. as seen in a single layer and multilayered periosteal reaction) in aggressive lesions, so only the edge of the raised periosteum will os...

Chronic unilateral airspace opacification (differential)

Chronic unilateral airspace opacification is a subset of the differential diagnoses for airspace opacification. An exhaustive list of all possible causes of chronic unilateral airspace opacities is long, but a useful framework is as follows: neoplastic post obstructive lymphoma lymphocytic ...

Chronic bilateral airspace opacification (differential)

Chronic bilateral airspace opacification is a subset of the differential diagnosis for airspace opacification. An exhaustive list of all possible causes of chronic bilateral airspace opacities is long, but a useful framework is as follows: inflammatory sarcoidosis granulomatosis with polyangi...

Chondrocalcinosis

Chondrocalcinosis (plural: chondrocalcinoses) is a descriptive term indicating the presence of gross calcium deposition within articular cartilage, i.e. both hyaline and fibrocartilage. Terminology Chondrocalcinosis articularis was an early term for calcium pyrophosphate dihydrate deposition d...

Cerebrovascular malformations

Cerebrovascular malformations are vascular malformations related to the vessels that supply the brain and other cranial structures. Classification Over the years, cerebral vascular malformations have been classified in a variety of ways by many authors, often on the basis of the presence or ab...

Brain herniation

Brain herniation, also referred to as acquired intracranial herniation, refers to shift of brain tissue from its normal location, into an adjacent space as a result of mass effect. It is a life-threatening condition that requires prompt diagnosis. Pathology There are a number of different pat...

Cerebellopontine angle mass

Cerebellopontine angle (CPA) masses are relatively common. Although a diverse range of pathologies may be seen in this region, the most common by far is vestibular schwannoma. Pathology Cerebellopontine angle masses can be divided into four groups, based on imaging characteristics: enhanc...

Central bronchiectasis

Distribution of bronchiectasis can help in narrowing the differential diagnosis. Central bronchiectasis is typically seen in: allergic bronchopulmonary aspergillosis (ABPA) congenital tracheobronchomegaly (also known as Mounier Kuhn syndrome) cystic fibrosis Williams Campbell syndrome (rare)...

Calcification of the globe (differential)

Calcification of the globe has many causes, varying from benign to malignant. When calcification is seen in the posterior half of the globe, it could relate to any of the layers (scleral, choroidal or retinal), as it is not possible to separate them out on CT. Retinal drusen: 1% population at ...

Bat wing opacities (lungs)

Bat wing opacities, also known as butterfly opacities, refer to a pattern of bilateral perihilar lung shadowing. It is classically described on a frontal chest radiograph but can also refer to appearances on chest CT 3,4. Differential diagnosis Bat wing pulmonary opacities can be caused by: ...

Basal ganglia T2 hypointensity

Basal ganglia T2 hypointensities can be caused by any of the following and is commonly remembered using the mnemonic ChOMP. childhood hypoxia old age multiple sclerosis Parkinson disease: more in globus pallidus Parkinson-plus syndrome: more in putamen deoxyhemoglobin of hemorrhage hemosi...

Basal ganglia calcification

Basal ganglia calcification is common and is seen in approximately 1% of all CT scans of the brain, depending on the demographics of the scanned population. It is seen more frequently in older patients and is considered a normal incidental and idiopathic finding in an elderly patient but should ...

Basal ganglia T1 hyperintensity

There are many causes of basal ganglia T1 hyperintensity, but the majority relate to deposition of T1-shortening elements within the basal ganglia such as: calcium idiopathic calcification calcium and phosphate abnormalities hepatic dysfunction or bypass (specifically affecting globi pallidi...

Basal ganglia T2 hyperintensity

The causes of basal ganglia T2 hyperintensity can be remembered using the mnemonic LINT: lymphoma ischemia hypoxic-ischemic encephalopathy venous infarction (internal cerebral vein thrombosis) neurodegenerative autoimmune encephalitis (e.g. anti-D2 dopamine antibody...

Anterior mediastinal mass

Anterior mediastinal masses can be caused by neoplastic and non-neoplastic pathology. These masses arise in the anterior mediastinum, that portion of the mediastinum anterior to the pericardium and below the level of the clavicles. Epidemiology The prevalence of anterior mediastinal masses on...

Air space opacities

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...

Acute airspace opacification with lymphadenopathy (differential)

Acute airspace opacification with lymphadenopathy is a subset of the differential diagnosis for generalized airspace opacification and includes: post-obstructive causes (usually chronic, but 'new' changes can occur) primary lung cancer pulmonary metastases lymphoma/leukemia infection prim...

Acute unilateral airspace opacification (differential)

Acute unilateral airspace opacification is a subset of the differential diagnosis for airspace opacification. Differential diagnosis The exhaustive list of all possible causes would be huge, but a useful framework includes: pus, i.e. pulmonary infection bacterial pneumonia fungal pneumoni...

Acute bilateral airspace opacification (differential)

Acute bilateral airspace opacification is a subset of the larger differential diagnosis for airspace opacification. An exhaustive list of all possible causes of acute bilateral airspace opacities is long, but a useful way to consider the huge list is via the material within the airways: in...

Venous thromboembolism

Venous thromboembolism covers a wide spectrum of diseases. Individual conditions and complicating condition include: head and neck cerebral vein thrombosis dural venous sinus thrombosis cavernous sinus thrombosis deep cerebral vein thrombosis cortical vein thrombosis superior ophthalmic v...

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