Photopsias are a visual phenomenon experienced by individuals with a variety of ocular or optic pathway pathology. In lay terms they represent flashing lights, and can be divided into unstructured or structured photopsias, the latter referring to geometric shapes 2.
Phrenic nerve palsy (also known as phrenic nerve paresis or paralysis) has many causes and can be caused by lesions anywhere along the course of the phrenic nerve, as it travels from the neck, to pierce the diaphragm adjacent to the pericardium.
No single demographic is affected, ...
Phthisis bulbi, also known as end-stage eye, is an atrophic scarred and disorganized globe that may result from a variety of severe ocular insults.
In general, phthisis bulbi involves elderly patients, usually 65-85 years of age 7. Children and adolescents are only rarely affecte...
Pineal parenchymal tumors comprise a group of related tumors ranging from the relatively benign to the highly malignant. This group comprises of:
14-30% of pineal parenchymal tumors 2
mature well-differentiated tumor
WHO grade I
pineal parenchymal tumor with intermediate differe...
A simple and popular mnemonic to remember the common suprasellar/parasellar/intrasellar masses is SATCHMO. The more comprehensive list includes:
pituitary adenoma (commonest in the adult population)
The five most common masses in the pituitary region are:
suprasellar pilocytic astrocytoma
Craniopharyngioma and suprasellar pilocytic astrocytoma are common in children, and pituitary macroadenoma, meningioma, aneurysm are mostl...
Pituitary region mass with an intrinsic high T1 signal, also referred as suprasellar hotspots, are relatively frequently encountered, and the presence of high T1 signal narrows the differential somewhat.
pituitary macroadenoma with hemorrhage/necrosis
Pituitary tumors, in other words, tumors which arise from the pituitary gland itself, include:
spindle cell oncocytoma (rare)
Often the term is used more broadly to refer ...
Placentomegaly is a term applied to an abnormally enlarged placenta.
It can be associated with a number of maternal and fetal disorders which include:
chronic intrauterine infections
Pleural adhesions usually refers to the formation of fibrotic bands that span the pleural space, between the parietal and visceral layers of the pleura.
They may be local or diffuse. The presence of a pleural adhesion is one of the causes for a pneumothorax not to resolve.
Pleural calcification can be the result of a wide range of pathology and can be mimicked by a number of conditions/artifacts.
calcified pleural plaques from asbestos exposure: typically with sparing of the costophrenic angles
infection involving the pleura: e.g....
Pleural effusions are abnormal accumulations of fluid within the pleural space. They may result from a variety of pathological processes which overwhelm the pleura's ability to reabsorb fluid.
"Pleural effusion" is commonly used as a catch-all term to describe any abnormal accumul...
Pleural involvement with lymphoma can occur in two situations:
primary pleural lymphoma
primary effusion lymphoma
secondary involvement of the pleura with lymphoma
Pleural thickening is a descriptive term given to describe any form of thickening involving either the parietal or visceral pleura.
It can occur with both benign and malignant pleural disease. According to etiology it may be classified as:
benign pleural thickening
following recurrent inflam...
There are several tumors that can involve the pleura which can range from being benign to malignant. The list includes:
primary pleural tumors
malignant pleural mesothelioma
pleural fibroma: solitary fibrous tumor of the pleura
primary pleural lymph...
Pneumatoceles are intrapulmonary air-filled cystic spaces that can have a variety of sizes and appearances. They may contain air-fluid levels and are usually the result of ventilator-induced lung injury in neonates or post-infectious. They should not be mistaken for a cavitating lung mass.
Pneumatosis coli is a descriptive sign presenting radiographically as intramural gas limited to the colonic wall.
There are different terminologies in the medical literature, such as pneumatosis intestinalis, pneumatosis coli, and pneumatosis cystoides intestinalis. Pneumatosis in...
Pneumoconioses are a broad group of lung diseases that result from inhalation of dust particles. It is therefore considered part of the spectrum of inhalational lung disease, and also occupational lung diseases.
The offending agents are mainly mineral dust. They can be broa...
Pneumonectomy is a radical lung surgery involving complete surgical removal of the lung. It is most commonly performed for a primary lung malignancy. The lung is removed in its entirety providing the patient has adequate pulmonary reserve from the contralateral lung.
Pneumonia is a general term in widespread use, defined as infection within the lung. It is due to material, usually purulent, filling the alveoli.
Pneumonia is in contrast to pneumonitis, which is inflammation of the pulmonary interstitium. Of note, some of the interstitial lung di...
Pneumoparotid refers to air in the parotid gland and can cause unilateral/bilateral parotid swelling. In severe cases it can be associated with subcutaneous emphysema.
Any profession or recreation that increases oral positive pressure can cause air to reflux up the parotid ducts int...
A pneumothorax does not display classical signs when a patient is positioned supine for a chest radiograph. Instead, the pneumothorax may be demonstrated by looking for the following signs:
relative lucency of the involved hemithorax
deep, sometimes tongue-like, costophrenic sulcus: deep sulcu...
Polyarticular arthropathy can arise from a number of causes. The list includes
Polyhydramnios refers to a situation where the amniotic fluid volume is more than expected for gestational age.
It is generally defined as:
amniotic fluid index (AFI) >25 cm
largest fluid pocket depth (maximal vertical pocket (MVP)) greater than 8 cm 6: although some centers, particularly in ...
Polymyalgia rheumatica (PMR) is a common inflammatory condition typically affecting elderly people. It is a multisystem disorder but usually affects the musculoskeletal system.
It can manifest in various ways, which are best discussed in the separate articles below:
polymyalgia rheumatica (mus...
Common causes of polyostotic bone lesions in adults include:
arthritic or synovial-based lesions
nonossifying fibromas (fibroxanthomas)
polyostotic fibrous dysplasia (McCune-Albright syndrome)
Porcelain left atrium, also known as coconut left atrium, is a term used when a large part of or the entire left atrial wall becomes calcified. It can occur as a rare consequence of endocarditis (with underlying rheumatic heart disease). It has also been described in the setting of end-stage ren...
Posterior fossa astrocytomas, those arising either from the cerebellum or from the brainstem are most frequently seen in children. Approximately 60% of all pediatric astrocytomas are found in the posterior fossa (20% brainstem, 40% cerebellum).
Many types of astrocytoma are found in the posteri...
The differential diagnosis for a posterior mediastinal mass includes:
neurogenic tumors - most common
nerve sheath tumors
malignant peripheral nerve sheath tumor
parasymphathetic ganglion tumors
Posterior shoulder dislocations are far less common than anterior shoulder dislocations and can be difficult to identify if only AP projections are obtained. A high index of suspicion is helpful.
Posterior shoulder dislocations account for only 2-4% of all shoulder dislocations (t...
Posterior vertebral fusion anomalies are relatively common and should not be mistaken for fractures. They are thought to be both developmental and pathological (e.g. spondylolysis) but are typically asymptomatic and incidental, and considered as anatomical variants. There are six types of poster...
Post-obstructive pulmonary edema is a type of non-cardiogenic pulmonary edema and is an uncommon but well-described complication of upper airway obstruction.
It essentially occurs in three clinical settings 6:
acute airway obstruction
chronic upper airway obstruction
Post-sternotomy complications comprise of a varied range problem that can occur at varying durations after a median sternotomy. Imaging playing in detection and aiding management.
Complication rates for median sternotomy have been reported to range from 0.5-5%, with mortality rate...
Post surgical breast scar is a benign complication that usually occurs following surgical intervention to breast tissue. It can however be a strong and potentially very confusing mimicker of breast malignancy.
Review of the patient's past history and previous mammography...
A Pott shunt is a form of palliative surgery performed in patients with tetralogy of Fallot prior to the ability to repair the defect. It consists of a shunt formed between the descending thoracic aorta and the left pulmonary artery.
This does not relieve the right ventricular outflow obstructi...
The Powers ratio is a measurement of the relationship of the foramen magnum to the atlas, used in the diagnosis of atlanto-occipital dissociation injuries.
The ratio, AB/CD, is measured as the ratio of the distance in the median (midsagittal) plane between the:
basion (A) and the posterior spi...
Pre-axial polydactyly refers to polydactyly where the additional digit is towards the first digit of the hand (radial side) or foot (medially).
Pre-axial polydactyly is less common than post-axial polydactyly, with an estimated incidence of 1 in 7000.
Pregnancy associated breast cancer (PABC) is usually defined as a breast cancer diagnosed during pregnancy or one year following delivery. PABC occurs in one out of every 1500-10,000 pregnancies 5-6 and represents up to 3% of all breast malignancies. The incidence may be increasing due to many w...
Pregnancy of uncertain viability (PUV) is a term given to an intrauterine pregnancy in a situation where there are not enough criteria (usually on ultrasound grounds) to confidently categorize an intrauterine pregnancy as either viable or a failed pregnancy.
Preinvasive lesions of the lung are those pulmonary lesions that have not yet progressed to malignancy but have the potential to do so. This category includes:
squamous dysplasia (SD) of lungs: squamous cell carcinoma in situ (CIS) of lung
preinvasive adenocarcinoma of the lung 5,6
Premature closure of a growth plate subsequently results in a shortened bone, which can occur in a number of situations.
juvenile chronic arthritis
juvenile rheumatoid arthritis
Primary benign cardiac tumors are much less common than secondary metastatic deposits. However they are more likely when a cardiac mass is seen outside of the setting of terminal metastatic disease. Tumors include 1-2:
most common in adults
accounts for ~50% of all primary beni...
The most common tumor of the spine is metastatic deposits. A number of both benign and malignant tumors may arise primarily from the spine.
giant cell tumor (GCT)
aneurysmal bone cyst (ABC)
eosinophilic granuloma (EG)
The primary immunodeficiency states are a heterogenous group of disorders that occur when there is an impairment of humoral or cell-mediated immunity in the absence of any recognized precipitating cause such as drug therapy or infective agent such as human immunodeficiency virus (HIV).
There are a number of primary malignancies of the nasopharynx:
nasopharyngeal carcinoma (squamous cell carcinoma): 70%
lymphoma (sinonasal lymphoma): 20%
nasopharyngeal papillary adenocarcinoma
adenoid cystic carcinoma
Primary malignant cardiac tumors are rare, and account for only ~25% of primary cardiac tumors, and only a small proportion of all malignant tumors which involve the heart: direct extension of adjacent tumors or metastatic deposits are far more common.
Histologcal types include 1:
Although primary tumors of the thymus are rare, they are the most common causes of a neoplasm of the anterosuperior mediastinum 1.
one-third are benign
two-thirds are malignant
invasive thymoma (most)
thymic carcinoma (rare)
Primary peritoneal neoplasms comprise an uncommon group of heterogeneous entities, which include:
primary (malignant) peritoneal mesothelioma
peritoneal multicystic mesothelioma
primary peritoneal well-differentiated papillary mesothelioma
primary peritoneal adenomat...
Primary pneumatosis intestinalis (PPI) is a benign idiopathic condition in which multiple gas-filled cystic lesions are seen in the gastrointestinal tract wall. The changes are usually seen initially on radiography or CT with CT being the more sensitive test.
Primary pneumatosis i...
Primary pulmonary tuberculosis is seen in patients not previously exposed to Mycobacterium tuberculosis.
It is most common in infants and children and has the highest prevalence in children under 5 years of age 1.
Primary pulmonary tuberculosis manifests as...
Programmable cerebrospinal shunts are a type of ventriculoperitoneal shunt that can be set to different CSF pressure settings. They are of particular value in normal pressure hydrocephalus and in pediatric patients.
The 2010 AJNR article by Lollis et al. 1 provides radiographic features (with r...
Proptosis refers to forward protrusion of the globe with respect to the orbit. There are many causes of proptosis which can be divided according to location and it is worth remembering that it is not just orbital disease processes that cause proptosis.
Exophthalmos also describes f...
Prosopagnosia is the inability to recognize faces. There are varying degrees of impairment and only the recognition of familiar faces can be affected. There is usually preservation of other aspects of visual processing and intellectual functioning. With the most extreme impairment the sufferer c...
Transrectal ultrasound–guided biopsy is considered the standard approach for prostate biopsy and is most commonly performed on an outpatient with a positive screening for prostate cancer.
Nowadays, with the MRI capacity for depicting abnormal areas of the prostate, is possible to obtain target...
Prostate cystic disease encompasses a wide variety of pathologies that all result in cyst formation within the prostate.
Prostatic cysts are common, and ~5-8% men will develop one 4,7. However they are much more common in patients being investigated for infertility, with one study showing a 20%...
Prostate peripheral zone T2 hypointensity is a common finding in pelvic MRIs that needs to be differentiated. A prostate directed MRI is usually performed using a multi-parametric technique to differentiate prostate cancer from more benign changes. This includes T2 weighted images, dynamic contr...
Prostatomegaly is a term used to generally describe enlargement of the prostate gland from whatever cause. Usually, the prostate is considered enlarged on imaging when it measures beyond 30 cc (30 grams) in size.
The term prostatomegaly is often used interchangeably with benign pr...
Prosthetic heart valves are common. The four valves of the heart may all be surgically replaced. However, the aortic and mitral valves are the most commonly replaced.
Replacements may be tissue or metallic valves, only the latter being visualized on imaging investigations. Sometimes the annulus...
Protean in standard English has the meaning of something that appears in many different forms. In the same vein, in radiological usage it is used to describe a condition which can assume multiple different guises. One of its classic uses is for the imaging appearance of osteomyelitis which can l...
Acetabular protrusio (also known as acetabular protrusion) is intrapelvic displacement of the acetabulum and femoral head, so that the femoral head projects medial to the ischioilial line. It should be differentiated from coxa profunda.
Protrusio acetabuli is divided into two types, ...
A pseudoarthrosis (or pseudarthrosis/ false joint) presents an abnormal union between parts of the bone that fractured spontaneously due to congenital weakness.
Differential diagnosis includes:
failed bone graft
neurofibromatosis type 1
Pseudobladder refers to a pelvic cystic mass that simulates the urinary bladder.
The location of the lesion should allow differentiation from the bladder but if doubt exists and clinical necessity arises, a delayed phase CT or MRI with excreted contrast or IDC-administered retrograde contrast f...
Pseudobulbar palsy is a clinical syndrome of dysarthria, dysphagia, a hyperactive gag reflex and labile emotional responses. It results from bilateral upper motor neuron brainstem lesions.
This is in contrast to bulbar palsy, which is a lower motor neuron syndrome involving the lowermost crani...
Pseudocirrhosis is a radiological term used to recapitulate imaging findings of cirrhosis, but occurring in the setting of hepatic metastases. It is most commonly reported following chemotherapeutic treatment of breast cancer metastases, although has also been reported before treatment, and with...
Pseudocyst of the humerus, also referred as a humeral head pseudolesion, is a normal anatomical variant due to increased cancellous bone in the region of the greater tuberosity of the humerus which is seen as a lucent lesion on radiography.
Hyperemia and disuse caused by shoulder problems (such...
Pseudodefect of capitellum refers to an abrupt contour change of the posterolateral margin of capitellum on coronal sections and is a potential MRI imaging pitfall giving rise to misinterpretations. It occurs because the width of the articular surface of the capitellum is non-uniform and gradual...
Pseudodislocation of the shoulder results from an occult fracture with distension of the glenohumeral joint due to hemarthrosis that causes inferior displacement of the humeral head compared to the glenoid.
This may be mistaken for shoulder joint dislocation. Often, attempts are made to "reloca...
Pseudohydronephrosis (plural: pseudohydronephroses) refers to normal anatomy or non-significant pathologies that may mimic hydronephrosis. There is usually fluid-density material within a dilated part of the urinary tract, but without other signs of obstruction such as retroperitoneal fat strand...
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, normalized for height and gender, with a resulting figure for PI in cm2/m2.
(RPA + LPA)/height2
While an effective standardized ...
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 recognized 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 or 2 cm in diameter (with the precise limit varying by source). Their walls are less than 1 mm thick. If they rupture, they allow air to escape into pleural space resulting in a spontaneous pneumothorax.
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)
intrathoracic portosystemic collateral vessel formation
The development of portal hypert...
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 hemorrhage 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
Pulmonary metastases are common and the result of metastatic spread from a variety of primary tumors via blood or lymphatics.
This article describes haematogenous pulmonary metastases with lymphangitis carcinomatosis discussed separately.
The epidemiology will match that of the u...
Pulmonary necrosis is seen in a variety of conditions, including 1:
Klebsiella pneumoniae - Klebsiella pneumonia
Haemophilus influenzae - pulmonary haemophilus influenzae infection
Pseudomonas aeruginosa - pulmonary pseudomonas aeruginosa infe...
Pulmonary neuroendocrine tumors are a group of lung tumors which are of neuroendocrine cell lineage. These are thought to arise from Kulchitzky cells and range from being low to high grade.
carcinoid tumors of the lung
bronchial carcinoid tumors
typical bronchial carcinoids
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.
Some patients are...
Pulmonary ossification is a rare finding and is characterized by the presence of mature bone in alveolar or interstitial spaces, either localized or disseminated throughout the lung parenchyma.
It can be idiopathic (idiopathic pulmonary ossification) or secondary to chronic lung, cardiac or sys...
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.