Pseudomeningocele refers to an abnormal collection of cerebrospinal fluid that occurs due to leakage from the CSF-filled spaces surrounding the brain and spinal cord as a result of trauma or surgery.
The salient feature of pseudomeningocele is that it contains CSF that communicates with the CSF...
A pseudopermeative process in bone has multiple small cortical holes that are then superimposed over the marrow, giving a similar appearance to a permeative process.
Most common pathologies that manifest with pseudopermeative appearance (and mimic permeative lesions) include:
Pseudopneumoperitoneum describes any gas within the abdominal cavity that masquerades as free intraperitoneal gas or pneumoperitoneum when it is in fact contained within an organ. Correctly identifying pneumoperitoneum is important, but making the diagnosis in error may lead to further unnecessa...
Patients with pseudopseudohypoparathyroidism (PPHP) have similar clinical and radiological features as pseudohypoparathyroidism but without alterations in parathyroid hormone levels and calcium metabolism. There is often a family history of pseudohypoparathyroidism.
Pseudosyndactyly refers to a mitten hand deformity of hands and feet in dystrophic epidermolysis bullosa. It may also be seen in amniotic band syndrome. It should not be confused with true syndactyly which is the actual and complete fusion of fingers. In pseudosyndactyly fingers are fused by thi...
Psoas index is an imaging marker of sarcopenia, which is a key component of frailty.
Using cross sectional imaging, psoas area values are computed 1,2, normalised for height and gender, with a resulting figure for PI in cm2/m2.
(RPA + LPA)/height2
While an effective standardised ...
Pulmonary angiitis and granulomatosis refers to group of conditions where there is a vascular (angiitis) as well as granulomatous component. At least five distinct clinical syndromes are known, which include:
eosinophilic granulomatosis with polyangiitis (previously known as Churg-Strauss syndr...
Pulmonary arterial calcification is the phenomenon which is usually seen in the setting of advanced pulmonary hypertension. It can however be uncommonly present in those without pulmonary hypertension.
The general mechanism in the vast majority is thought to be from high end pulmonar...
Pulmonary aspergillosis is a collective term used to refer to a number of conditions caused by infection with a fungus of the Aspergillus species (usually Aspergillus fumigatus).
There are a number of recognised pulmonary forms, the number depending on the author 1,3-4 . Each form has specific ...
Pulmonary blebs are small subpleural thin walled air containing spaces, not larger than 1-2 cm in diameter. Their walls are less than 1 mm thick. If they rupture, they allow air to escape into pleural space resulting in a spontaneous pneumothorax.
Blebs are a very common finding ...
Pulmonary calcification has many causes and varying morphology:
calcific pulmonary nodules or masses
calcified granulomas, e.g. prior thoracic histoplasmosis, recovered miliary tuberculosis (rare)
healed varicella pneumonia
Pulmonary cavities are thick-walled abnormal gas-filled spaces within the lung. They are usually associated with a nodule, mass, or area of consolidation. A fluid level within the space may be present. Plain radiography and CT form the mainstay of imaging.
According to the Fleischn...
There are several pulmonary complications that can arise in the setting of cirrhosis:
hepatopulmonary syndrome (HPS): considered the commonest
portopulmonary hypertension (POPH)
hepatic hydrothorax (HH)
Dyspnoea and arterial hypoxemia are the most common symptoms.
Pulmonary fibrosis is a descriptive term given when there is excess of fibrotic tissue in lung. It can occur in a wide range of clinical settings and can be precipitated by a multitude of causes. The term should not be confused with idiopathic pulmonary fibrosis which is a progressive fibrotic l...
Pulmonary fungal disease encompasses a broad spectrum of infections related to fungal sources. They can particularly affect immunocompromised individuals.
pulmonary aspergillosis: pulmonary aspergillus infection considered the most important in immunocompromised individuals 5
Pulmonary haemorrhage is a rather broad term given to describe any form of bleeding into the lung and can arise from a myriad of causes. In a very traditional sense it is described when the following constellation of clinico-radiological features occur simultaneously 2 (although this is never an...
Pulmonary hypertension has many causes, and these can be divided in many ways. A simple and systematic approach is to proceed along the cardiopulmonary pulmonary circulation, as causes are found at each site (for a more official classification system see 2003 third world symposium on pulmonary a...
Pulmonary infections are common and are caused by a wide range of organisms.
Micro-organisms responsible may enter the lung by three potential routes:
via the tracheobronchial tree
most commonly due to inhalation of droplets of secretions from another infected human
The term "pulmonary infiltrate" is considered a context-dependent, non-specific and imprecise descriptive term when used in radiology reports (plain film or CT).
From a pathophysiological perspective, the term "infiltrate" refers to “an abnormal substance that accumulates gradually within cells...
Pulmonary metastases are common and the result of metastatic spread from a variety of primary tumours via blood or lymphatics.
This article describes haematogenous pulmonary metastases with lymphangitis carcinomatosis discussed separately.
The epidemiology will match that of the ...
Pulmonary necrosis is seen in a variety of pulmonary infections including 1:
Klebsiella pneumoniae - Klebsiella pneumonia
Haemophilus influenzae - pulmonary haemophilus influenzae infection
Pseudomonas aeruginosa - pulmonary pseudomonas aeruginosa infection
Pulmonary neuroendocrine tumours are a group of lung tumours which are of neuroendocrine cell lineage. These are thought to arise from Kulchitzky cells and range from being low to high grade.
carcinoid tumours of the lung
bronchial carcinoid tumours
typical bronchial carcinoid...
Pulmonary nodules are small, rounded opacities within the pulmonary interstitium. Pulmonary nodules are common and, as the spatial resolution of CT scanners has increased, detection of smaller and smaller nodules has occurred, which are more often an incidental finding.
Pulmonary non-tuberculous mycobacterial (NTM) infection refers to pulmonary infection caused by one of the large number (at least 150) mycobacterial species other than Mycobacterium tuberculosis. However, certain species are much more common than others.
As with M. tuberculosis NTMs ...
Pulmonary ossification (PO) is a rare finding and is characterised by the presence of mature bone in alveolar or interstitial spaces, either localised or disseminated throughout the lung parenchyma.
It can be idiopathic (idiopathic pulmonary ossification) or secondary to chronic lung, cardiac o...
Pulmonary vasculitis refers to vasculitides that affect the lung or pulmonary vessels. If this definition is used, a large group of conditions can fall into this category. The respiratory system may be potentially involved in all systemic vasculitides, although to a variable degree.
Pulsatile exophthalmos or pulsatile proptosis is a clinical symptom characterized by protrusion and pulsation of the eyeball that can occur due to various causes:
neurofibromatosis type 1 (with sphenoid wing dysplasia)
trauma (orbital roo...
The clinical symptom of pulsatile tinnitus can occur from a number of causes. They include
dehiscent jugular bulb
high riding jugular bulb
laterally placed sigmoid sinus
abnormal mastoid emissary veins
aberrant internal carotid ...
Pure ground glass lung nodules are a subtype of ground glass lung nodules where there is no associated solid component.
They have been shown to represent various pathologies such as 1,3
adenocarcinoma in situ of lung
minimally-invasive adenocarcinoma of lung
invasive adenocarcinoma of lung
Purely intrasellar pituitary masses have a similar differential as the more generic pituitary region mass gamut, or the mnemonic SATCHMO, although some entities are far more common than others.
Rathke cleft cyst
Pyelonephritis refers to an upper urinary (renal) tract infection with associated renal pelvis, renal calyceal and renal parenchymal inflammation, and comprises a heterogeneous group of conditions.
Pyometrium refers to infection of the endometrial cavity with resulting expansion due to accumulated pus (pyometra).
The post-menopausal demographic are most commonly affected due to the association with uterine malignancy.
endometritis / pelvic inflammatory disease
Pyopneumothorax (also known as infected hydropneumothorax or empyemic hydropneumothorax) is a pleural collection of pus and air. It may be thought of a variant of a thoracic empyema with air containing components although the aetiology may be different.
The patient usuall...
Rachitic rosary refers to expansion of the anterior rib ends at the costochondral junctions and is most frequently seen in rickets as nodularity at the costochondral junctions.
Other causes of this appearance include:
the costochondral junction is more angula...
Ranawat's line is the perpendicular distance between the centre of the sclerotic ring of C2 and a line drawn along the axis of the C1 vertebra.
Normal value is 17 mm in males and 15 mm in females. It is decreased in basilar invagination.
History and etymology
Chitranjan S Ranawat is an Americ...
RASopathies are a class of developmental disorders caused by germline mutations in genes that encode for components or regulators of the Ras/mitogen-activated protein kinase (MAPK) pathway.
As a group, RASopathies represent one of the most common malformation syndromes, with an in...
Radiological manifestations of recreational drug use are not infrequently seen as the use of recreational drugs is widespread.
Interestingly, recent reports have suggested a decreasing incidence of reported drug use in the general population over the past decade, but it remains th...
Rectal foreign bodies are not uncommon in emergency departments around the world, and although they are often the source of endless amusement do potentially cause management difficulties.
The incidence varies according to the region, said to be uncommon in Asia and most common in ...
Complete fatty replacement of red marrow with fat on MRI can occur in a number of situations which includes:
regional radiation therapy
Reeder and Felson's Gamuts in Radiology, first published in 1975, provided comprehensive lists of radiological differential diagnoses, or gamuts, and was a bestseller for many years. The current publisher is Springer.
The first edition was edited and, primarily, written by Ben Felson and Mauric...
Regional osteopenia describes a localised or regional decrease in bone mineral density.
disuse osteopenia (usually an aggressive osteoporosis with pseudopermeative pattern)
immobilisation of fractures
bone and joint infections
complex regional pain...
Renal artery dissection may occur as a result of the following processes 1:
aortic dissection extending to involve the renal artery
iatrogenic (e.g. catheterisation)
connective tissue disease (eg. Marfan syndrome)
Renal artery stenosis (RAS) 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.
When the stenosis occurs slowly, collateral vessels form and supply the kidne...
Renal cortical defects have a variety of causes, and present on imaging as an area of focal cortical thinning or absence of renal cortex, sometimes accompanied by focal caliectasis.
The differential diagnosis for a renal cortical defect includes 1,2:
Renal papillary necrosis refers to ischemic necrosis of the renal papillae. Necrosis also occurs in the medullary pyramids.
Patients can present with both acute episodes or chronic renal papillary necrosis. Calyceal or ureteral obstruction by sloughed papillae manifest with f...
A renal pseudotumour is a mass that will simulate a tumour on imaging but is composed of non-neoplastic tissue. There are many examples 1:
prominent column of Bertin
persistent fetal lobulation
cross-fused renal ectopia
renal hilar lip
Renal transplantation is one, if not the most, common transplant procedures undertaken worldwide. Consequently, purposeful and incidental imaging of renal transplants and renal transplant-related complications are increasingly common. These include acute renal transplant rejection and chronic re...
Renal vein varices develop for various reasons and are usually asymptomatic.
Renal vein varices are usually asymptomatic. Some patients may present with flank pain and/or haematuria.
chronic renal vein thrombosis
Renovascular hypertension (RVH) is a type of secondary hypertension, where high blood pressure develops secondary to renal artery disease.
Approximately 2.5% (range 0.5-5%) of hypertensive patients will have RVH as a cause 2,3.
There are a number of condit...
A residual breast cancer is a remaining portion of the original primary breast cancer after an incomplete resection or following radiotherapy or chemotherapy. The term is particularly used in assessing patients who have had neo-adjuvant chemo +/- radiotherapy.
A number of toxins affect the respiratory chain and result in typical changes within the brain.
inhibits electron transfer and avidly binds to haemoglobin displacing oxygen
globus pallidus typically affected
see: carbon monoxide poisoning
metabolised to ...
Respiratory failure is a term to denote when the respiratory system fails in one or both of its gas exchange functions: oxygenation and carbon dioxide elimination. This results in arterial oxygen and/or carbon dioxide levels being unable to be maintained within their normal range. While it is no...
Response evaluation criteria in solid tumours or RECIST refers to a set of published rules used to assess tumour burden in order to provide an objective assessment of response to therapy. They were initially introduced in 2000 and have undergone subsequent revision in 2009 (RECIST 1.1). For the ...
Restrictive cardiomyopathy is the least common subtype of cardiomyopathy and is characterised by a marked decrease in ventricular compliance.
Patients can present with symptoms and signs of left ventricular failure and/or right ventricular failure 9.
It is p...
Retained gallstones are common during a laparoscopic cholecystectomy, with a reported incidence of 0.1–20%, and occur when gallstones are inadvertently spilled into the peritoneal cavity.
When recognised intraoperatively spilled stones should be retrieved to avoid potential complications includ...
The term retrolisthesis (more rarely the synonyms retrospondylolisthesis or posterolisthesis) refers to posterior displacement (backward slip) of a vertebral body relative to one below. Causes include trauma, facet joint osteoarthritis or congenital anomalies (e.g. underdevelopment of the pedicl...
A retropulsed fragment is any vertebral fracture fragment that is displaced into the spinal canal, thereby potentially causing spinal cord injury.
They usually arise from the vertebral body with or without a portion of the pedicle, and are displaced posteriorly, hence the prefix 'retro'.
Reverse bat wing pulmonary opacities refer to peripheral opacities of the lungs, sparing the perihilar region. It is a relatively unusual appearance with a relatively narrow differential:
chronic eosinophilic pneumonia
organising pneumonia (formerly bronchiolitis obliterans with organising pne...
Rhizomelic dwarfism is a type of dwarfism where the dominant feature is proximal (i.e. femoral, humeral) limb shortening.
The following conditions fall under the heading of rhizomelic dwarfism 3
rhizomelic chondrodysplasia punctata
Rib fractures are a common consequence of trauma and can cause life-threatening complications.
The 4th-10th ribs are the most commonly fractured 1. Fractures of the 1st-3rd ribs are associated with high-energy trauma 3.
When the rib is fractured twice, the term floating rib is used ...
Rib notching refers to deformation of the superior or inferior surface of the rib. It can affect a single rib (from trauma or solitary masses e.g. schwannoma) or can affect multiple ribs.
The differentials differ according to whether it is the superior or inferior surfac...
Right atrial enlargement is less common, and harder to delineate on chest radiograph, than left atrial enlargement.
Enlargement of the right atrium can result from a number of conditions, including:
raised right ventricular pressures
pulmonary arterial hypertension
Right heart strain (or more precisely right ventricular strain) is a term given to denote the presence of right ventricular dysfunction usually in the absence of an underlying cardiomyopathy. It can manifest as an acute right heart syndrome.
Right heart strain can often occur as a re...
Right iliac fossa mass is a common clinical presentation and has a range of differentials that need to be excluded. Radiology plays an important role in this differentiation.
Right lower lobe collapse has distinctive features, and is usually relatively easily identified. The absence of overlying cardiomediastinal outline makes it easier to appreciate than left lower lobe collapse.
For a general discussion please refer to the article on lobar collapse.
Right middle lobe collapse (or simply termed middle lobe collapse) has distinctive features, but can be subtle on frontal chest radiographs.
For a general discussion please refer to the article on lobar collapse.
It is important to note that of all the lobes, the right middle lobe is the mo...
Risk factors for testicular germ cell tumours (GCT) include:
Caucasians at higher risk than African Americans (9:1)
10-40x increased risk
around 10% of all tumours are associated with undescended testis
higher risk if intra-abdominal testis compared with intra-inguinal
In many centers, laparoscopic Roux-en-Y gastric bypass has become the most common bariatric procedure for morbid obesity.
In this operation, the stomach is stapled or divided to form a small pouch (typically <30 mL in volume), which empties into a Roux limb of the jejunum of varying length (ty...
The rule of 4 of the brainstem was devised by Peter Gates, an Australian neurologist, in 2003 in order to simply explain the anatomy of the brainstem and basis of brainstem stroke syndromes to the non-neurologist and medical student 1-3. This article summarises Gates' four rules, associated impo...
A very wide range of lesions can occur in and around the sacrum.
primary sacral tumours
sacral chordoma: most common primary sacral tumour 1
Ewing sarcoma / pPNET
osteosarcoma: often arises from Paget's disease in this location
Sacroiliitis (inflammation of the sacroiliac joint) can be a manifestation of a wide range of disease processes. The pattern of involvement is helpful for narrowing down the differential diagnosis.
Usually bilateral and symmetrical
Salivary gland tumours are variable in location, origin, and malignant potential.
In general, the ratio of benign to malignant tumours 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 a...
Head and neck manifestations of sarcoidosis can have three main forms:
orbital involvement: orbital sarcoidosis
parotid gland involvement
nodal involvement: cervical lymphadenopathy in sarcoidosis
A scalp haematoma usually occurs following an injury at delivery although they are commonly seen with head trauma.
There are three types of haematoma, which are defined by their location within the scalp, particular their location as related to the galea aponeurosis and skull pe...
The scapholunate angle is the angle between the long axis of the scaphoid and the mid axis of the lunate on the sagittal imaging of the wrist. In a normal situation it should be between 30o and 60o in the resting (neutral) position.
The scapholunate angle is abnormal in carpal instability:
Scapula fractures are uncommon injuries, representing ~3% of all shoulder fractures.
Mechanisms of injury
requires high energy trauma (e.g. motor vehicle accidents account for 50% of scapular fractures)
direct trauma to the shoulder region
indirect trauma through falling on outstr...
The Scham sign of slipped capital femoral epiphysis is one of the subtle signs that may be seen on the AP view of an adolescent hip with early slip.
In the normal adolescent hip, an intraarticular portion of the diaphysis of the collum overlies the posterior wall of the acetabulum inferiomedial...
Scheuermann disease, also known as juvenile kyphosis, juvenile discogenic disease 11, or vertebral epiphysitis, is a common condition which results in kyphosis of the thoracic or thoracolumbar spine. The diagnosis is usually made on plain film.
occurs in ~5% (range 0.4-8%) of the ...
Sciatic hernia is a rare type of pelvic floor hernia, which occurs through either the greater or lesser sciatic foramina. It can contain variable structures.
curlicue ureter sign
SCIWORA is the abbreviation of spinal cord injury without radiographic abnormality 1,2. This can be an indication for MRI when there is a persisting, objective myelopathy after a traumatic event with normal plain film and CT findings. It accounts for ~10% of spinal cord injuries.
Sclerosing bone dysplasias comprise a heterogeneous group of disorders (skeletal dysplasias) united by the presence of sclerosis of one form or another. Some of these entities are thought to be related (e.g. osteopoikilosis, melorheostosis and Buschke-Ollendorff syndrome) 1.
Sclerotic or blastic bone metastases can arise from a number of different primary malignancies including 1-5:
prostate carcinoma (most common)
breast carcinoma (may be mixed)
transitional cell carcinoma (TCC)
mucinous adenocarcinoma of the gastroint...
Sclerotic clavicles have many causes:
trauma: fractured clavicle
arthritis: osteoarthritis, seronegative arthritides
osteitis condensans of the clavicle 1
Scoliosis is defined as an abnormal lateral curvature of the spine. It is quite common in young individuals and is often idiopathic and asymptomatic. In some cases, however, it is the result of underlying structural or neurological abnormalities.
By definition, a scoliosis is any lateral spina...
There are few areas in imaging specifically and in medicine in general, fraught with more controversy than screening for breast cancer. Due to the emotive issues surrounding the diagnosis, the scientific literature on breast screening and its issues reaches the lay press quickly and is sometimes...
The scrotum and its content are subject to a number of infective processes including:
Scrotal tunica cysts are paratesticular cystic lesions. They include:
tunica vaginalis cysts
tunica albuginea cysts
Typically seen as a simple appearing paratesticular cystic lesion not in the region of the epididymis.
Secondary organising pneumonia (SOP) refers to organising pneumonia that can be attributed to a specific cause, in contrast to cryptogenic organising pneumonia (COP).
SOP can be attributed to the following causes 1:
atypical pneumonias (e.g. Leg...
Semimembranosus tendon avulsion is a specific type of avulsion injury that can occur in the knee.
Mechanism of injury
External rotation and abduction of the flexed knee or valgus force applied to the tibia. Associated injuries include anterior cruciate ligament (ACL) rupture and po...
Sensorineural hearing loss (SNHL) refers to deafness secondary to conditions affecting the inner ear, internal acoustic canal, cerebellopontine angle, or vestibulocochlear nerve.
Conditions that cause SNHL can be divided by location:
otosclerosis (and othe...
Seronegative spondyloarthritides, also known as spondyloarthropathies (SpA), are a group of musculoskeletal syndromes linked by common clinical features and common immunopathologic mechanisms. The subtypes of spondyloarthritis are usually distinguished on the basis of the patient’s history and c...
The shaggy heart border is a descriptive term referring to the ill definition of the cardiac silhouette on a chest radiograph. Due to its imprecise nature, some caution is advised against its use in radiological reports 4.
It usually implies pleural disease on the mediastinal interface 3 and ma...
Shifting granuloma sign refers to a shift in the location of a parenchymal lesion visible on prior films that may be seen in the presence of atelectasis.
For example, this occurs when a calcified granuloma is present in a lung and a significant parenchymal collapse "shifts" it from one location...