The C sign is an important radiological sign which may be seen on a lateral radiograph of ankle in those with a tarsal coalition (talocalcaneal coalition).
A continuous C-shaped arc is seen on a lateral ankle radiograph which is formed by the medial outline of the tal...
CA 19-9 is a serum antigen (monosialoganglioside) that has increased diagnostic use in the management of several malignancies, mainly of hepato-pancreatico-biliary origin. It is nonspecific, however, and can rise in both malignant and nonmalignant conditions.
Elevation of serum CA 19-9 has been...
Serum CA-125 is well recognised as an ovarian cancer-associated marker and is an antigen determinant on a high-molecular-weight glycoprotein. The normal range of CA-125 is 0-35 U/mL.
Serum CA-125 levels can also be used to monitor the response to treatment as well as a prognostic indicator sinc...
The Cabrol shunt or Cabrol fistula, also known as a perigraft-to-right atrial shunt, is a technique used for uncontrolled bleeding following aortic root operations.
The Cabrol shunt is applied when bleeding from an aortic root reconstruction cannot be controlled by traditional means ...
Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL) is an autosomal dominant microvasculopathy, characterised by recurrent lacunar and subcortical white matter ischaemic strokes and vascular dementia in young and middle age patients without known ...
The caecal bar sign is a secondary sign in acute appendicitis. It refers to the appearance of inflammatory soft tissue at the base of the appendix, separating the appendix from the contrast-filled caecum.
Caecal bascule is an uncommon type of caecal volvulus. It occurs in a large and mobile caecum that folds up over itself resulting in closed obstruction to the caecal pole and appendix.
Clinical presentation and treatment are not significantly different to the more common axial caecal volvulus.
Caecal volvulus describes torsion of the caecum around its mesentery which often results in obstruction. If unrecognised, it can result in bowel perforation and faecal peritonitis.
Caecal volvulus accounts for ~10% of all intestinal volvuluses, and generally occur in somewhat youn...
The caecum is the first part of the large bowel and lies in the right lower quadrant of the abdomen.
Blind-ending sac of bowel that lies below the ileocaecal valve, above which the large intestine continues as the ascending colon. The caecum measures 6 cm in length and can have ...
Caesarean scar ectopic pregnancy (CSEP) is a rare type of abnormal implantation. It is often considered the rarest type of ectopic pregnancy, although some do not include it in this category as implantation occurs within the uterus.
It has an estimated incidence of ~1:1800-2200 pr...
Café au lait spots are a type of pigmented skin lesions which are classically described as being light brown in colour.
Conditions associated with them include:
neurofibromatosis type 1 (NF1)
McCune-Albright syndrome: typically irregular which has been likened to ...
Caffey disease or infantile cortical hyperostosis is a largely self-limiting disorder which affects infants. It causes bone changes, soft-tissue swelling, and irritability.
A rare variant known as prenatal onset cortical hyperostosis is severe and fatal, though it is probably a separate entity ...
Caisson disease is an uncommon diving-related decompression illness that is an acute neurological emergency typically occurring in deep sea divers.
Diving-related decompression illness is classified into two main categories 3:
Arterial gas embolism secondary to pulmonary decompression barotra...
Calcaneal fractures are the most common tarsal fracture, and can occur in a variety of settings.
The calcaneus is the most commonly fractured tarsal bone and accounts for about 2% of all fractures 2 and ~60% of all tarsal fractures 3.
Calcaneal fractures can be divided...
The calcaneal inclination angle is drawn on a weightbearing lateral foot radiograph between the calcaneal inclination axis and the supporting surface.
It is a measurement that reflects the height of the foot framework, but is affected by abnormal pronation or supination of the foot:
The calcaneal inclination axis is drawn between the most inferior portion of the calcaneal tuberosity and the most distal and inferior point of the calcaneus at the calcaneocuboid joint on a weightbearing lateral foot radiograph.
It can be used to draw the calcaneal inclination angle.
A mnemonic for calcaneal lesions is:
B: bone cyst (unicameral)
I: intraosseous lipoma
G: ganglion (intraosseous)
G: giant cell tumour
The calcaneal (Achilles) tendon is the strongest and largest tendon in the foot and even in the human body. But it is commonly injured tendon in the foot owing to scanty vascularity and high pressure upon it. As it carries the whole body weight during standing 2.
The calcaneal te...
Avulsion fractures of the calcaneal tuberosity are rare, accounting for only 3% of all calcaneal fractures. There is a strong association with diabetes, where they may occur spontaneously, and are thought to be due to peripheral neuropathy. They also occur in osteoporosis and hyperparathyroidism...
Calcaneal vascular remnant is a benign finding that may be seen on MRI of ankle and can be misinterpreted as an alarming bone lesion. It is typically located at the insertion site of sinus tarsi ligaments (cervical and interosseous ligaments).
The focus of signal alteration is believed to be pr...
The calcaneofibular ligament (CFL) is the middle ligament of the lateral collateral ligament complex of the ankle and stabilises both the ankle and subtalar joints.
The CFL is an extracapsular round cord measuring 20-25 mm long x 6-8 mm width. Its origin is distal to the anterior...
Calcaneonavicular coalition is one of the two most common subtypes of tarsal coalition, the other being talocalcaneal coalition. As with any coalition it may be osseous (synostosis), cartilaginous (synchondrosis) or fibrous (syndesmosis).
This type of coalition is more ea...
The calcaneus, also referred to as the calcaneum, is the largest tarsal bone and the major bone in the hindfoot. It articulates with the talus superiorly and the cuboid anteriorly and shares a joint space with the talonavicular joint, appropriately called the talocalcaneonavicular joint. The cal...
Calcaneus axial view is part of the two view calcaneus series, this projection is best used to asses the talocalcaneal joint and plantar aspects of the calcaneus. The axial view has a diagnostic sensitivity of 87% for calcaneus fractures 1.
patient is supine or seated with th...
Calcaneus lateral view is part of the two view calcaneus series; this projection is used to assess the calcaneus, talocrural, talonavicular and talocalcaneal joint.
the patient is in a lateral recumbent position on the table
the lateral aspect of the knee and ankle joint shou...
The calcaneus series is comprised of a lateral and axial (plantodorsal) projection. The calcaneus is the most commonly fractured tarsal bone accounting for ~60% of all tarsal fractures 1. This series provides a two view investigation of the calcaneus alongside the talar articulations and talocal...
A calcaneus x-ray, also known as calcaneus series or calcaneus radiograph, is a set of two x-rays of the calcaneus. It is performed to look for evidence of injury (or pathology) affecting the leg, often after trauma.
This is a summary article. For more information, you can re...
The calcar femorale is a normal ridge of dense bone that originates from the postero-medial endosteal surface of the proximal femoral shaft, near the lesser trochanter. It is vertical in orientation, and the ridge projects laterally toward the greater trochanter. This ridge of bone provides mech...
The calcarine artery, named according to its course in the calcarine fissure, is a branch of the posterior cerebral artery, usually from the P3 segment. It may also arise from the parieto-occipital artery or posterior temporal branches. It courses deep in the fissure, giving branches both to th...
The calcarine fissure, or calcarine sulcus, is located on the medial surface of the occipital lobe and divides the visual cortex (a.k.a. calcarine cortex) into two.
The fissure is variable in course (figure 1), but is generally oriented horizontally, anteriorly joining the parieto-occipital fi...
Calcific axillary lymphadenopathy is in general, more concerning than axillary lymphadenopathy alone and is particularly so if it contains microcalcifications. While this is concerning for malignancy, it can also occur from occasional nonmalignant causes
metastatic axillary lymp...
Calcific bursitis is the result of deposition calcium hydroxyapatite crystals. It is closely related to calcific tendinitis, and many authors refer to them as being the same condition.
In mammography, the term calcific cluster is usually given to where at least five microcalcifications in one cubic centimetre (that is 1 square cm) on two projections on a non-magnified contact view 1.
Homogeneous, smooth clustered microcalcifications can be due to 2:
Calcific myonecrosis refers to a rare post-traumatic phenomenon. It characterised by latent formation of a dystrophic calcified mass occurring almost exclusively in the lower limb (it has been occasionally reported at other sites 5).
Plain radiographs typicall...
Calcification associated with pulmonary emboli is usually associated with chronic pulmonary embolism. They are occasionally be related to prior congenital cardiac repairs 1.
If it is purely high attenuating, consider
polymethylmethacrylate (PMMA) embolism into lungs
Calcific tendinitis is a self-limiting condition due to deposition of calcium hydroxyapatite within tendons, usually of the rotator cuff. It is a common presentation of the hydroxyapatite crystal deposition disease (HADD).
Typically this condition affects middle-aged patients bet...
Calcific tendinitis of the longus colli muscles is an inflammatory/granulomatous response to the deposition of calcium hydroxyapatite crystals in the tendons of the longus colli muscle.
This condition typically occurs in adults in middle age (20-50 years of age) with a slight pred...
Calcification of the external ear (auricular cartilage) may arise from a number of causes, including:
gout and pseudogout
Calcification of the globe has many causes, varying from the benign to malignant. When calcification is seen of 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.
drusen: 1% population...
Calcified cerebral embolus is an uncommon and often overlooked cause of embolic ischaemic stroke.
Although emboli are a common cause of ischaemic stroke, calcified cerebral emboli are considered rare. With only a paucity of literature regarding calcified cerebral emboli – only 48...
Calcified intra-articular lesions have a relatively limited differential, including:
impaction fracture fragments
intraarticular avulsion fractures
There are numerous causes of calcified mediastinal lymph nodes.
Common causes include:
infectious granulomatous diseases
Uncommon causes include:
Pneumocystis jiroveci (PCP) pneumonia
thyroid carcinoma: papi...
Calcified pulmonary (lung parenchymal) densities can occur in a number of conditions.
healed varicella pneumonia 1
pulmonary alveolar microlithiasis
occupational lung diseases
coal workers pneumoconiosis
Large nodules or masses
Calcified pulmonary nodules are a subset of hyperdense pulmonary nodules and a group of nodules with a relatively narrow differential.
The most common cause of nodule calcification is granuloma formation, usually in the response to healed infection.
A calcified yolk sac has been described as a sign of intrauterine demise. The cause of yolk sac calcification in failed pregnancies is uncertain but is likely related to dystrophic calcification.
abnormal increased echogenicity of the yolk sac with posterior a...
Calcifying epithelial odontogenic tumour, also known as a Pindborg tumour, is typically located in the premolar and molar region of the mandible, although up to a third are found in the maxilla.
Usually they are seen in the 4th to 6th decades. They are rare tumours.
Calcifying fibrous pseudotumours (CFPT) of the lung are very rare, benign lesions of the lung.
They are composed of hyalinised collagen with psammomatous-dystrophic calcification and a typical pattern of lymphocytic inflammation.
CFPTs usually occur within soft tissues but have be...
A simple mnemonic to recall a list of commonly calcifying metastases is:
B: breast cancer
T: papillary thyroid cancer
O: ovarian cancer (especially mucinous)
M: mucinous adenocarcinoma (especially colorectal carcinoma)
Calcifying pseudoneoplasms of the neuraxis (CAPNON) are rare non-neoplastic, non-inflammatory heavily calcified discrete intraparenchymal or extra-axial lesions of CNS. The most common location is temporal region.
They usually asymptomatic and found incidentally but somet...
Calcifying pulmonary metastases are rare. These should not be confused with metastatic pulmonary calcification.
Calcification in metastases can arise through a variety of mechanisms: bone formation in tumours osteoid origin, calcification and ossification of tumour cartilage, dystrop...
Calcinosis circumscripta is a condition involving calcium deposition in the subcutaneous tissues, muscles and fascia. It is considered a localised form of calcinosis cutis universalis most often seen in the hands and feet.
Patients present with firm white dermal papules, ...
Calcinosis universalis is a condition characterised by long bands or sheets of symmetrical subcutaneous calcification.
It usually presents <20 years of age, and is more common in women.
palpable calcific plaques in subcutaneous or deeper tissue
fatigue, muscle pain, and...
Calciphylaxis, or calcific ureamic arteriolopathy, is a rare condition which manifests as subcutaneous vascular calcification and cutaneous necrosis (small blood vessels of the fat tissue and the skin). Some authors describe as a syndrome of vascular calcification, thrombosis and skin necrosis.
Calcium pyrophosphate dihydrate disease (CPPD disease), also referred as pyrophosphate arthropathy and perhaps confusingly as pseudogout, is common, especially in the elderly, and is characterised by the deposition of calcium pyrophosphate in soft tissues and cartilage.
CPPD is on...
The Caldwell-Luc operation uses an external approach for surgical treatment of the severely diseased maxillary sinus. It is an alternative to middle meatal antrostomy done via endonasal endoscopic surgery and was the primary approach used for accessing the maxillary sinus before the advent of en...
Although described as a separate condition, Call-Fleming or Call syndrome is a subset of reversible cerebral vasoconstriction syndrome. It is characterized by a history of thunderclap headache with subsequent beaded appearance of the Circle of Willis on angiographic imaging (as seen in RCVS), bu...
The callosal angle has been proposed as a useful marker of patients with idiopathic normal pressure hydrocephalus (iNPH), helpful in distinguishing these patients from those with ex-vacuo ventriculomegaly (see hydrocephalus versus atrophy).
Ideally the angle should be measured on a cor...
The callosal sulcus is a sulcus of the brain, located on the medial side of each cerebral hemisphere, deep within the medial longitudinal fissure.
The callosal sulcus runs posteriorly from the genu to the splenium of the corpus callosum. It separates the cingulate gyrus dorsally...
The callosomarginal artery (also known as median artery of corpus callosum) is the largest branch of the pericallosal artery. It runs in or posteriorly to the cingulate sulcus and runs a course parallel to the pericallosal artery where it divide to give two or more cortical branches to supply th...
The callososeptal interface is located on the inferior surface of the corpus callosum, when the septum pellucidum abuts it.
It came to radiological attention when T2 hyperintense lesions affecting this region were believed to be specific for multiple sclerosis. This has, as is usually the case...
Calot triangle is a small (potential) triangular space at the porta hepatis of surgical importance as it is dissected during cholecystectomy. Its contents, the cystic artery and cystic duct must be identified before ligation and division to avoid damaging them during the operation.
Calvarial thickening can occur from a number of causes. These include
chronic ventricular shunting1
anaemias (largely associated with massive haematopoiesis)
Calvarial thinning can result from many causes. They include:
craniofacial syndromes 1
focal calvarial thinning
The calyceal crescent sign (Dunbar's crescents) refers to the early IVP appearance of markedly dilated renal calyces. It is formed by early contrast opacification of the dilated collecting ducts and ducts of Bellini with the characteristic shape as a result of the associated enlarged calyces.
Calyceal diverticula, also known as pyelocalyceal diverticula are congenital outpouchings from the renal calyx or pelvis into the renal cortex. These diverticula are lined with transitional cell epithelium.
Relatively uncommon, seen in 0.21% to 0.60% of intravenous urograms (IVU)....
Calyceal microlithiasis or more specifically renal calyceal microlithiasis is defined as <3 mm hyperechoic foci noted within the renal calyces on gray scale ultrasonography 1. It has been considered as a precursor for renal stone formation.
The patient may be asymptomati...
Camptocormia (bent spine syndrome) is a rare syndrome characterised by involuntary flexion of the thoracolumbar spine with weight-bearing which reduces when laying down, and is due to isolated atrophy of the paraspinal muscles.
This condition may be associated
Parkinson disease: ...
Camptodactyly is a clinical or imaging descriptive term where there is a flexion contracture (usually congenital) classically at the proximal interphalangeal joint.
The age of presentation can vary from being detected in utero in an antenatal scan or as an obvious deformi...
Camptodactyly arthropathy coxa vara pericarditis (CACP) syndrome is a rare condition principally characterised by
congenital or early-onset camptodactyly and childhood-onset non-inflammatory arthropathy
coxa vara deformity or other dysplasia associated with progressive hip disease
Camptomelic dwarfism, also known as camptomalic dysplasia, is a rare form of skeletal dysplasia.
Camptomelic dwarfism is rare with an estimated incidence of ~1:200,000 births.
Diagnosis is usually readily made at birth or with antenatal ultrasound. It is...
Camurati-Engelmann disease (CED), also known as progressive diaphyseal dysplasia (PDD), is a rare autosomal dominant sclerosing bone dysplasia. It begins in childhood and follows a progressive course.
Common symptoms include extremity pain, muscle weakness, cranial nerve ...
Canadian C-spine rules are a set of guidelines that help a clinician decide if cervical spine imaging is not appropriate for a trauma patient in the emergency department. The patient must be alert and stable.
There are three rules:
is there any high-risk factor present that requires cervical s...
The Canadian CT head rule (CCTHR) is a validated clinical decision rule to determine the need for CT head in adult emergency department patients with minor head injuries.
Patient has suffered minor head trauma with resultant:
loss of consciousness
The canal of Nuck is an abnormal patent pouch of parietal peritoneum extending anteriorly from the round ligament of the uterus into the labia majora through the inguinal ring into the inguinal canal. Incomplete obliteration of this canal is known as a patent processus vaginalis and can result i...
The canals of Lambert are microscopic collateral airways between the distal bronchiolar tree and adjacent alveoli. They are poorly formed in children, and along with poorly formed pores of Kohn, are thought to be responsible for the high frequency of round pneumonia in that age group.
Canavan disease, also known as spongiform degeneration of white matter (not to be confused with Creutzfeldt-Jakob Disease) or aspartoacylase deficiency, is a leukodystrophy clinically characterised by megalencephaly, severe mental and neurological deficits, and blindness.
Cancer is clearly a huge topic and this page is merely a starting point for what will become a much larger article that links to a myriad of articles and cases. For further information about staging in cancer, see the separate article. Some of the headings are taken from the AJCC cancer staging ...
Cancer staging using a number of systems to help direct treatment and aid prognosis.
FIGO (in gynaecological cancer)
Dukes staging system
breast cancer staging
non-small cell lung cancer staging
small cell lung cancer staging
Candida oesophagitis is the most common cause of infectious oesophagitis that commonly affects immunocompromised patients. On imaging, it is characterised by irregular plaque-like lesions separated by normal mucosa and small (<1cm) ulcers, which are assessed on oesophagogram studies.
Candida pneumonia is form of pulmonary candidiasis where there is air space opacification due opportunistic infection by the fungus Candida albicans. It typically occurs in immunocompromised patients. Due to the organism normally being present as part of oro-pharyngeal flora the diagnosis is oft...
Cannonball metastases refer to large, well circumscribed, round pulmonary metastases that appear, well, like cannonballs. The French term "envolée de ballons" which translates to "balloons release" is also used to describe this same appearance.
Metastases with such an appearance are classically...
Cantlie's line is a vertical plane that divides the liver into left and right lobes creating the principal plane used for hepatectomy. It extends from the inferior vena cava posteriorly to the middle of the gallbladder fossa anteriorly.
It contains the middle hepatic vein which divides the live...
Capillary haemangiomas of the orbit, also known as strawberry haemangiomas, on account of its colouring, or orbital infantile haemangiomas, are the most common orbital tumours of infancy, and unlike orbital cavernous haemangiomas, they are neoplasms rather than vascular malformations.
Capitalisation is a potential area where style differences can make a significant difference to the content at Radiopaedia.org, and as usual, a consistent style is crucial for uniformity of the site.
Titles and subheadings
Article titles and case titles, as well as subheadings, should be in s...
The capitate (or os magnum) is the largest of the carpal bones and sits at the centre of the distal carpal row. A distinctive head shaped bone, it has a protected position in the carpus.
The capitate sits in a proximo-distal direction with a waist that is proximal to...
Capito-hamate coalition is the second most common type of carpal coalition and represents congenital fusion of the capitate and the hamate. It represents ~5% of all carpal fusions 1 and is associated with Apert syndrome 2.
The capitolunate angle is the angle between the long axis of the capitate and the mid axis of the lunate on the sagittal imaging of the wrist. In a normal situation it should be less than 30o in the resting (neutral) position.
The angle is increased in carpal instability such as with a dorsal i...
Caplan syndrome, also known as rheumatoid pneumoconiosis, is the combination of seropositive rheumatoid arthritis and a characteristic pattern of fibrosis.
Although first described in coal miners (coal workers' pneumoconiosis), it has subsequently been found in patients with a variety of pneumo...
A capnothorax, sometimes referred to as a carbon dioxide (CO2) pneumothorax, has been reported as a potential complication with laparoscopic surgeries.
It has been reported with almost all laparoscopic surgeries and is more likely to occur with high CO2 pressures and prolonged sur...
The Capp triad refers to the constellation of clinical and imaging findings in patients with spontaneous retropharyngeal haematomas, and consists of:
tracheal and oesophageal compression
anterior displacement of the trachea
subcutaneous bruising over the neck and anterior chest
Capsular contractures are a potential complication of a breast implant and refers to a tightening and hardening of the capsule that surrounds a breast implant. It is a condition that can distort the shape and cause pain in the augmented breast. It seems to be the commonest complication post-brea...
There is variation in the relationship between the glenoid labrum and the anterior shoulder joint capsule. This has been divided into three types:
Type 1: capsule inserts into the labrum proper
Type 2: capsule inserts into the base of the labrum, or within 1cm of the base
Type 3: capsule inse...
Each study has a caption, located above the images, which is optional but should ideally represent the kind of study without the diagnosis e.g.
CT abdomen and pelvis
Three phase liver CT