Mucinous cystic neoplasms of the pancreas are the most common cystic neoplasm of the pancreas and include:
mucinous cystadenoma of pancreas
mucinous cystadenocarcinoma of pancreas
intraductal papillary mucinous neoplasms (IPMN) of the pancreas: sometimes classified separately
A mucocele simply refers to accumulation and expansion of a structure by mucus. It occurs in a variety of locations which are discussed separately:
paranasal sinus mucocele
oral cavity e.g. ranula, mucous retention cysts
mucocele of the appendix 1
mucocele of the gallbladder
mucocele of the...
Mucoid impaction, also referred to as mucus plugging or bronchocele, airway filling by mucoid secretions and can be obstructive or non-obstructive. It is a common pathological finding in chest imaging.
Mucoid impaction may result from either obstructive or non-obstructive ...
Mucopolysaccharidoses (MPS) constitute a group of hereditary disorders, one of a number of lysosomal storage disorders, having in common an excessive accumulation of mucopolysaccharides secondary to deficiencies in specific enzymes (lysosomal hydrolases) responsible for degradation of mucopolysa...
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
Multicentric reticulohistiocytosis (MRH) also known as lipoid dermatoarthritis, is a rare systemic disorder.
MRH is considered a form of granulomatous disease 10 characterised by infiltration of multinucleated histiocytes into various tissues, primarily affecting skin and synovium, w...
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.
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.
The most common causes of multiple cranial nerve thickening and enhancement include:
metastasis (most common)
neurofibromatosis type II
lymphoma and leukaemia
chronic inflammatory demyelinating polyneuropathy
cranial nerve enhancement: for compl...
The differential diagnosis for multiple cystic neck lesions is different to that for a solitary cystic neck mass.
Cystic neck lesions are seen in:
necrotic metastatic SCC nodes: older patient, M>F
papillary thyroid carcinoma metastases: usually a younger patient, F>M
Multiple endocrine neoplasia (MEN) syndromes are a collection of syndromes characterised by the presence of, as the name would suggest, multiple endocrine tumours. They are autosomal dominant in inheritance.
MEN1 (Wermer syndrome)
MEN2 (multiple endocrine adenomatosis)
MEN2a (Sipple syndrome)...
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)
multiple ureteral stones (steinstrasse)
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...
Myelination of the brain during infancy progresses in an orderly and predictable fashion which can be assessed with MRI.
At birth only certain structures are myelinated:
central corticospinal tracts
posterior limb of the internal ca...
Myocardial perfusion and viability assessment is important for many reasons:
to diagnose, locate and grade the severity of coronary artery disease
to identify candidates who would benefit from re-vascularization
to evaluate response of re-vascularization
Myometrium cysts are cysts seen in the myometrium and these can be differentiated appropriately based on location and sonological or Doppler features.
adenomyosis: the cysts are most often seen in the endomyometrial junction region. They ideally are small <5 mm, however ma...
Myonecrosis is a myopathy involving infarction of skeletal muscle and can have the appearances of an intramuscular mass.
Myonecrosis has a variety of causes 1,2:
sickle cell crisis
post-traumatic (see: calcific myonecrosis)
Named fractures are usually eponymous or occupational. The simplest way of spiting them up is by body area:
upper extremity fractures
lower extremity fractures
A narrow fetal thorax on antenatal ultrasound can be present with a number of anomalies which include:
Jeune syndrome - asphyxiating thoracic dysplasia
short rib polydactyly syndr...
The interpedicular (IP) distance which is the distance measured between the pedicles on frontal / coronal imaging can be narrowed in a number of situations
thanatophoric dysplasia 2
widening of interpedicular distance
See reference 1 for an old b...
Neonatal encephalopathy is a clinical syndrome referring to signs and symptoms of abnormal neurological function in the first few days of life in a neonate born at or beyond 35 weeks of gestation. It is described as difficulty with initiating and maintaining respiration, depression of tone and r...
Neonatal lines and tubes are widely used in the NICU (neonatal intensive care unit) in the management of critically ill neonates. Examples include:
nasogastric (NG) tube
endotracheal (ET) tube
central venous line
umbilical artery catheter
umbilical vein catheter
The NG tu...
Causes of neonatal distress can be broadly split into intrathoracic, extrathoracic and systemic:
respiratory distress syndrome (RDS)
transient tachypnoea of the newborn (TTN)
meconium aspiration syndrome
bronchopulmonary dysplasia (BPD)
patent ductus arteriosus (PDA)...
There are a number of neoplasms that can involve the vermiform appendix, some of which are peculiar to this site.
Tumours involving the appendix have been found in only about 1% of all appendectomy specimens 9. Epithelial neoplasms and neuroendocrine tumours represent the vast maj...
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 tumours
Nephrocalcinosis, previous known as Anderson-Carr kidney or Albright's calcinosis, refers to the deposition of calcium salts in the parenchyma of the kidney. It is divided into several types, with differing aetiologies, based on the distribution:
medullary nephrocalcinosis: 95%
Nerve root enhancement is phenomenon described on post contrast MRI scans that can be observed in a number of situations.
post-operative nerve root enhancement
disseminated spinal leptomeningeal metastases
Neuroblastic tumours arise from primitive cells of the sympathetic system and include the following entities:
These entities represent a spectrum of disease from undifferentiated and aggressive (neuroblastoma) to the well differentiated and l...
Both neuroblastoma and Wilms tumour occur in early childhood and typically present as large abdominal masses closely related to the kidneys. Distinguishing between the two is important, and a number of features are helpful.
calcification very common: 90%
encases vascular structu...
Neurofibromatoses (NF) comprise of a number of clinically and genetically distinct inherited conditions that carry a high risk of tumour formation. They fall under the wider classification of phakomatoses. The tumours particularly involve the central and peripheral nervous systems:
Nightstick fractures are isolated fractures of the ulna, typically transverse and located in the mid-diaphysis and usually resulting from a direct blow. It is a characteristic defensive fracture when the patient tries to ward off an overhead blow from an assailant (or local law enforcement offic...
Nipple markers can be a useful technique in the evaluation of densities overlying the expected position of the nipple on a chest radiograph. Not uncommonly a small round opacity projects over the lower thorax on a chest radiograph (see: solitary pulmonary nodule).
Often, especially in women, th...
Nipple shadows refer to the silhouettes of the nipples on frontal chest radiographs.
Nipple shadows are apparent on ~7.5% (range 3.5-11%) of frontal chest x-rays 1.
It has been proposed by Miller et al. that solitary pulmonary nodules that reach some or all of the foll...
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
Nodular pleural thickening is a form of pleural thickening.
Essentially all common causes of nodular pleural thickening are malignant and include:
metastatic pleural disease, particularly from adenocarcinomas, e.g.
Non-accidental injuries (NAI) represent both ethical and legal challenges to treating physicians.
Radiologists are often the first to suspect NAI when confronted with particular injury patterns, and a knowledge of these is essential if the opportunity to save a child from future neglect is not ...
Non-calcified hyperdense pulmonary nodules are predominantly the result of inhalational exposure to substances, although embolisation of material may cause dense nodular opacification within the lung.
inhalation disease, e.g. pneumoconioses
pulmonary baritosis (barium dust)
Non-neoplastic solid lesions of the pancreas (NNSLP) are conditions which may mimic pancreatic neoplasms on imaging. They include:
intrapancreatic accessory spleen
peripancreatic lymph node
congenital anomalies, such as prominent pancreatic ...
Non-seminomatous germ cell tumours (NSGCT) is one of the main groups of germ cell tumours (the other being seminoma). Although they are made up of distinct histological entities, in general, they have similar radiographic appearances. They can, however, be found widely in the body, with variable...
Non small-cell lung cancer represents a heterogeneous group of lung cancers that do not have small-cells on histology. They are thus separated, as small cell carcinoma of the lung has distinctive management implications. The major histological types include:
adenocarcinoma of lung
Normal intracranial calcifications can be defined as all age-related physiologic and neurodegenerative calcifications that are unaccompanied by any evidence of disease and have no demonstrable pathological cause.
The most common sites include:
seen in 2/3 of the adult population ...
A list of normal radiological reference values is as follows:
adrenal gland: <1 cm thick, 4-6 cm length
aorta: <3 cm diameter
appendix: on CT <6 mm calibre
adults: <3 mm
children: <5 mm
azygous vein: on erect chest x-ray <10 mm diameter
bladder wall: <3 mm (well-di...
Obesity is defined as a body mass index (BMI) greater than 30 kg/m2. It is described as being a "modern epidemic" due to increased rates of metabolic syndrome and other complications in these patients, along with a high and increasing prevalence.
Obesity rates vary around the wor...
Obstruction of nasolacrimal drainage apparatus results in epiphora and can be primary or secondary, congenital or acquired. Obstruction can occur in canaliculi, lacrimal sac, or nasolacrimal duct (post saccular) levels.
Congenital obstruction is usually secondary to persistence of the membrane ...
An obstructive uropathy is a catch-all term encompassing any cause of complete or partial, congenital or acquired and permanent or intermittent obstruction to the urinary tract. Depending on the severity of obstruction and extent, it may result in permanent change in both the collecting system p...
Occult fractures are those that are not visible on imaging, most commonly plain radiographs and sometimes CT, either due to lack of displacement or limitations of the imaging study. There may be signs of a fracture without one actually being seen. MRI or nuclear medicine studies are sometimes re...
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 tumours.
This article will discuss metastatic lesions affecting the orbits. For other intracranial metast...
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 ...
Odontohypophosphatasia is the mildest form of hypophosphatasia that manifests as tooth dysplasia and/or early loss of deciduous or permanent teeth.
As with all forms of hypophosphatasia, the underlying abnormality is a mutation in the ALPL gene that encodes for tissue non-specific al...
Oesophageal dysmotility refers to the pathological disruption of the normal sequential and coordinated muscle motion of the oesophagus to transport food from the oropharynx to the stomach. It is an umbrella term used to refer to the common pathophysiological endpoint of dysmotility that can be c...
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.
The estimated prevalence can be up to ~6% of pregnancies 4.
The causes of oligohydramnios are pr...
Oligometastases refers to distant disease that is limited in number and distribution, Niibe et al. defined this as ≤5 metastatic/recurrent lesions with control of the primary lesion 1,2. These metastases can be treated with local measures (surgery, radiation therapy, etc.) with the aim of increa...
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.
The most common cause is metasta...
Omphalomesenteric fistula occurs as aresult of failure of obliteration of the omphalomeseneric duct. It is one of the congenital fistulas of gastrointestinal tract .
Treatment of choice is often a partial trans umbilical resection with umbilical restitution.
Open reduction-internal fixation, commonly abbreviated to ORIF, refers to the orthopaedic operative management of a fracture (or fracture-dislocation complex) where reduction requires surgical (hence open) approach and internal fixation is applied.
Internal fixation may be in the form of:
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...
Enlargement of the optic nerves is uncommon and has a surprisingly broad differential:
optic nerve glioma
optic nerve meningioma
Several cystic and cyst-like orbital lesions may be encountered in imaging of the orbits:
developmental orbital cysts
dermoid: commonest benign orbital tumour in childhood
congenital cystic eye
The differential diagnosis of orbital inflammatory diseases (including orbital pseudotumours) can be divided based on their location into:
dacryoadenitis of lacrimal glands
myositis of extraocular muscles
perineuritis of optic nerve
An orbital mass carries a relatively wide differential:
lacrimal gland or duct tumours
rhabdomyosarcoma of the orbit
optic nerve meningioma
optic nerve glioma
optic nerve schwannoma
developmental orbital cysts 3:
Orbital vascular lesions may be difficult to distinguish on imaging. However, the following conditions have been described:
lymphangioma / lymphangiovenous malformation / venolymphatic malformation
orbital venous malform...
Apophyses are identical to epiphyses as far as differential diagnosis of lytic lesions, with exception of geodes, which only occur adjacent to articular surfaces.
chondroblastoma (Codman tumour)
clear cell chondrosarcoma
giant cell tumour (after fusion of epiphyseal plate; originates in metap...
Osteoarthritis of the vertebral column, also known as spondylosis deformans, is common and usually merely referred to as spinal "degenerative change". Complications such as spinal stenosis are important to recognise.
The hallmark of osteoarthritis in the spine, as is the...
Elbow involvement in osteochondritis dissecans is rare. It is defined as a localised fragmentation of bone overlying the capitellum cartilage. For a general discussion of osteochondritis dissecans refer to the parent article - osteochondritis dissecans.
Most commonly seen in young...
Osteochondrosis is the descriptive term given to a group of disorders that affect the progress of bone growth by bone necrosis. It is only seen in children and adolescents who are still growing.
The commoner examples include:
The differential diagnosis for osteoid lesions includes:
bone island (enostosis)
associations: osteopoikilosis, osteopathia striata, melorheostosis
Osteoporosis circumscripta cranii (also known as osteolysis circumscripta) refers to discrete radiolucent regions of the skull on plain radiographs. They are often seen in context of the lytic (incipient-active) phase of Paget disease of the skull, but may be observed in other circumstances as w...
The differential for osteoporosis includes:
mastocytosis (mast cells produce heparin)
Otitis media refers to inflammation or infection of the middle ear cavity. It is commonly seen in children and is termed otomastoiditis when inflammation spreads to involve the mastoid.
Common complaints include otalgia, otorrhoea, headache, fever, and systemic upset. In ...
Ovarian cystic neoplasms can be either benign or malignant and can arise from epithelial, stromal, or germ cell components. In general, the risk of malignancy in unilocular cystic tumours <10 cm in women over the age of 50 years is thought to be low 3-4.
ovarian mature cystic teratoma
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:
Ovarian tumours are relatively common and account for ~6% of female malignancies. This article focuses on the general classification of ovarian tumours. For specific features, refer to the subarticles.
Primary ovarian tumours
Surface epithelial-stromal ovarian tumours (60-...
There are several ovarian tumours associated with endometrial thickening and is often due to oestrogenic effects of the ovarian tumour.
Such tumours include:
ovarian epithelial tumours
endometroid carcinoma of the ovary
may have synchronous endometrial carcinoma or endometrial hyperplasia, p...
Oxalosis results in supersaturation of calcium oxalate in the urine (hyperoxaluria), which in turn results in nephrolithiasis and cortical nephrocalcinosis.
This article focus on the secondary oxalosis, please refer to primary oxalosis for a specific discussion on this entity.
The differential diagnosis of paediatric cervical lesions is commonly encountered in practice, unfortunately, the list is long.
Most lesions tend to be inflammatory 3:
infected branchial cle...
The clavicle is a unique bone and as such it often displays unique pathology. The following is an attempt to summarise paediatric clavicle abnormalities.
Paediatric bone tumours and tumour-like lesions of the clavicle
majority of clavicular tumours are malignant
Ewing sarcoma (most common)
The paediatric curriculum is one of our curriculum articles and aims to be a collection of articles that represent the core paediatric knowledge.
Topics pertaining to paediatric radiology, including paediatric neuroradiology and fetal radiology, although there will be some cross cov...
Paediatric nasal cavity masses can occur within the nose or the nasopharynx. These masses are often found incidentally on imaging but can be readily apparent clinically.
The clinical features of these lesions tend to mimic upper respiratory processes and may result in del...
Paediatric renal tumours 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.
Wilms tumour: common in older children 1-8 years old
There is a wide range of primary malignancies that results in paediatric skeletal metastases 1:
leukaemia: although not truly metastases
clear cell sarcoma: Wilms’ variant
Ewing’s sarcoma: lung metastases much more common
Pancreatic atrophy is non-specific and is common in elderly patients, although in younger patients it can be a hallmark of pathology. Most commonly it is associated with aging, obesity and end-stage chronic pancreatitis.
It occurs principally with fatty replacement of the pancreas (pancreatic ...
Pancreatic calcifications can arise form many aetiologies.
Punctate intraductal calcifications
acute alcoholic pancreatitis (20-40%)
intraductal, numerous, small, irregular
preponderant cause of diffuse pancreatic intraductal calcification
idiopathic: no underlying ca...
There are numerous primary pancreatic neoplasms, in part due to the mixed endocrine and exocrine components.
Classification based on function
exocrine: ~99% of all primary pancreatic neoplasms
pancreatic ductal adenocarcinoma ~90-95%
intraductal papillary muc...
Pancreatitis refers to inflammation involving the pancreas.
It has various forms which can be classified in many many ways according to time of onset, aetiological agent or associated pathology.
interstitial oedematous pancreatitis
A pantaloon hernia (dual hernia or Romberg's hernia or saddle bag hernia) is defined as ipsilateral, concurrent direct and indirect inguinal hernias. Hernial sacs are present on both sides of the inferior epigastric vessels, and separated by the posterior wall of the inguinal canal brought down ...
Papillary lesions of the breast comprise of a wide group and can range from being benign to malignant.
They develop as tufts of epithelium with a ﬁbrovascular core that arborize into branching papillae and protrude into the duct lumen.
papilloma of breast / intraductal papil...
Paralabral cysts are type of cyst located adjacent to a cartilage labrum of large joints. They are typically described in the shoulder and hip. Please refer to the sub-articles of discussion of these.
paralabral cyst of the shoulder
paralabral cyst of the hip
Parasyndesmophytes or floating syndesmophytes are, as the name suggests, paravertebral dystrophic soft tissue calcifications or heterotopic ossifications.
They are known to be seen in psoriatic arthritis and reactive arthritis 4.
Initially they begin at a dist...
Paratesticular lesions have a large list of differential diagnosis:
epididymal cyst (most common epididymal mass)
adenomatoid tumour (most common epididymal tumour)
scrotal tunica cysts
tunica vaginalis cyst
tunica albuginea cyst
A paratesticular mass may derive from a number of structures that surround the testicle within the scrotum; most commonly, they derive from the spermatic cord.
The masses can be categorised as benign (70%) or malignant (30%).
spermatic cord lipoma (most common pa...
Parkinson-plus syndrome refers to a loose group of neurodegenerative disorders that are characterised by features of Parkinson disease but with other neurological symptoms/signs. They have a poor response to levodopa, and mostly have fairly characteristic neuroimaging features.
Parotid enlargement (also known as parotidomegaly) has a wide differential given the significant breadth of pathology that can affect the parotid gland. These can be separated by the standard surgical sieve approach into infective, inflammatory, immune, neoplastic, infiltrative, and congenital c...
Patella alta, or a high riding patella, describes a situation where the position of the patella is considered high. It may be idiopathic or may result secondary to a patellar tendon rupture.
Several conditions are known to be associated with patella alta, including:...