Pancreatitis (plural: pancreatitides) refers to inflammation involving the pancreas.
It has various forms which can be classified in many many ways according to time of onset, etiological agent or associated pathology.
interstitial edematous pancreatitis
A pantaloon hernia (dual hernia, Romberg 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 by t...
Papillary lesions of the breast comprise a wide group and range from 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 papilloma of the b...
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 long list of differential diagnoses:
epididymal cyst (most common epididymal mass)
adenomatoid tumor (most common epididymal tumor)
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 categorized as benign (70%) or malignant (30%).
spermatic cord lipoma (most common par...
Parkinson-plus syndrome refers to a loose group of neurodegenerative disorders that are characterized 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...
Passive atelectasis, also known as relaxation atelectasis, refers to a form of lung atelectasis due to loss of the negative pressure state in the pleural space. With a loss of the negative intrapleural pressure, the lung is no longer held against the chest wall and is said to relax back to its n...
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:...
Patella baja (or patella infera) is an abnormally low lying patella, which is associated with restricted range of motion, crepitations, and retropatellar pain. If longstanding, extensor dysfunction may ensue with significant morbidity. It is seen in a variety of clinical scenarios including 1:
Patellar tendon rupture is one of the extensor mechanism of the knee injuries and occurs almost invariably at either the patellar or tibial insertion of the patellar tendon, when in the setting of trauma, and is often associated with a small avulsion fracture. Most commonly, it is at the superi...
Patellar tumors are extremely rare. They can be either benign or malignant primary bone tumors, or metastases.
Patellar tumors represent just 0.1% of all primary bone tumors 1.
Patients may present with anterior knee pain and/or a palpable mass 1,3.
Some medical conditions are characterized by the presence of pathological gas i.e. gas/air found in a space, tissue, or organ, where it would not normally be expected to be.
prefix 'pneumo' is common, especially when it refers to gas within a body space/cavity e.g. pneumothorax
Pattern of bone contusion in knee injuries can give clues for the mechanism and associated injuries.
Five classic bone contusion patterns have been described 1-4:
valgus stress to flexed and externally rotated knee
contusion pattern: posterolateral ...
Neonatal hypoxic ischemic brain injuries can manifest in different patterns of involvement depending on the severity and timing of the insult. When considering the perinatal maturation process of the brain and the severity of an insult, it is possible to understand the various manifestations.
Pear-shaped (or teardrop-shaped) bladder is one whose normal round or ovoid shape has been extrinsically compressed to resemble a pear. The pear may be inverted or upright, depending on how the excess pelvic tissue compresses the bladder.
Causes of a pear-shaped bladder inc...
A pedunculated intratracheal mass has a variety of differential diagnoses:
benign tumor, e.g. hamartoma, chrondroma, lipoma
metastasis to tracheal mucosa, e.g. renal cell carcinoma, melanoma
polyp, e.g. inflammatory, antrochoanal
Pelvic digit, also known as a pelvic rib, pelvic finger or 11th finger, is a rare congenital abnormality where there is development of bony tissue in the soft tissue pelvis and less commonly in the abdomen. They can be associated with one or more pseudoarticulation. They are usually unilateral, ...
Pelvic masses in females carry a broad differential diagnosis:
benign adnexal cyst: 34%
pelvic malignancy: 14%
pelvic inflammatory disease: 8%
Extra-gynecological masses, e.g. colorectal carcinom...
It is important to have a systematic way of approaching a case with pelvic pain in the exam.
Most examinations are performed using ultrasound. Always say that you would further assess the uterus with 3D ultrasound. You may also say that in my department we would perform a sonohysterogram. Only...
Pencil-in-cup deformity is the description given to one of the appearances on plain radiograph in psoriatic arthritis.
The appearance results from periarticular erosions and bone resorption giving the appearance of a pencil in a cup.
Although classically described with psoriatic arthritis, thi...
Penetrating traumatic neck injury can be a potentially devastating injury due to the high density of crucial anatomical structures within the neck.
Young males are highly represented in patients with a traumatic neck injury. In one study, 11:1 ratio of males to females were ident...
Periampullary tumors are those that arise within 2 cm of the ampulla of Vater in the duodenum.
Tumors that fall under this group include four main types of tumors 1,4 that will be approached in their specific articles:
pancreatic head/uncinate process tumors: includes pancreatic ductal adenoca...
Common causes of periarticular soft tissue calcification include:
post surgical dystrophic calcification or heterotopic bone formation
calcific tendinitis or bursitis
calcific periarthritis (fingers and toes)
Pericardial calcification usually occurs in patients with a history of pericarditis.
previous trauma or prior pericarditis
later sequelae of rheumatic heart disease
malignant pericardial involvement (e.g. mediastinal teratoma)
On chest radiography, the location ...
Pericardial fat pads are normal structures that lie in the cardiophrenic angle. They are adipose tissues surrounding the heart composed of the epicardial fat, which lies between the myocardium and visceral pericardium, and paracardial fat, which is adherent and external to the parietal pericardi...
Perifissural lung nodules (PFNs) are a type of intrapulmonary nodules that, most of the times, represent pulmonary lymph nodes.
Although perilymphatic pulmonary nodules can also be perifissural in distribution, they should be distinguished from PFNs, as they are usually associate...
Perigestational hemorrhage refers to hemorrhage that occurs around the fetus during the gestational period. The spectrum of hemorrhage includes:
chorionic hemorrhage: caused by the separation of the chorion from the endometrium
subchorionic hemorrhage: most common type, occurs between the cho...
Perilymphatic lung nodules follow perilymphatic channels and on imaging are typically subpleural, occur along fissures, interlobular septae and adjacent to the bronchovascular bundles.
Lung nodules in a perilymphatic distribution can be seen in association with a number ...
Perinephric fluid collections are commonly seen after renal transplantation. The appearance of a perinephric fluid collection is often nonspecific but may be partially differentiated by when the transplant occurred.
Early post-transplant period (<4 weeks)
Periosteal reaction in the pediatric population, also known as periostitis in children, is relatively common occurrence and can result from many causes.
The differential diagnosis for multiple bone periostitis include but not limited to the following:
Periosteal reaction, also known as periostitis or periosteitis, is a non specific radiographic finding that occurs with periosteal irritation. Periosteal reactions may be broadly characterized as benign or aggressive, or more specifically broken down by pattern.
Benign versus ag...
Periportal hyperechogenicity can result from many causes including:
schistosomiasis of the portal region
recurrent pyogenic cholangitis (oriental)
inflammatory bowel disease: has been described to give "echo-rich" periportal cuffing 2
Periportal hypoechogenicity can result from many causes:
orthotopic liver transplant rejection
malignant lymphatic obstruction
Peritoneal calcification is seen in a limited number of conditions that result in calcification of peritoneal structures. Therefore, the differential diagnosis is small:
psammoma bodies in malignancy (most frequently cystadenocarcinoma of the ovary): fine sand-like calcification
Peroneal tubercle hypertrophy refers to the presence of an unusually large peroneal tubercle.
Two bony projections or protuberances may be seen from the lateral wall of the calcaneus – the peroneal tubercle and the retrotrochlear eminence.
The peroneal tubercle is presen...
It is important to have a systematic way of approaching a case with per vaginal bleeding in the exam.
intrauterine fetal demise
Pes planus (also called flatfoot) is a deformity of the foot where the longitudinal arch of the foot is abnormally flattened.
It results from loss of the medial longitudinal arch and can be either rigid or flexible. These deformities are usually flexible, which means that on non-weig...
PET-CT is a combination of cross-sectional anatomic information provided by CT and the metabolic information provided by positron emission tomography (PET).
PET is most commonly performed with 2-[F-18]fluoro-2-deoxy-D-glucose (FDG). Fluorine-18 (F-18) is an unstable radioisotope and has a half-...
There is a wide differential diagnosis of petrous apex lesions:
asymmetrical marrow / asymmetrical pneumatization
fat signal intensity on all sequences
petrous apex cephalocoele 4
CSF signal intensity on all sequences
Phleboliths are literally "vein stones", and represent calcification within venous structures. They are particularly common in the pelvis where they may mimic ureteric calculi, and are also encountered frequently in venous malformations. There is an association with Maffucci syndrome.
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 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, as there are numerous causes of a phrenic nerve pa...
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.
The globe is reduced in size (usually <20 mm) with a thickened/folded posterior sclera. Dystrophic calcification is common, and osseous...
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 the 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.
Recognized post-pneumonectomy complications include:
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...
Pneumoretroperitoneum is by definition presence of gas within the retroperitoneal space.
Pneumoretroperitoneum is always abnormal and has a relatively small differential:
perforated retroperitoneal hollow viscus
peptic ulcer disease
blunt or penetrating abdominal trauma
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...
Portal venous gas is the accumulation of gas in the portal vein and its branches. It needs to be distinguished from pneumobilia, although this is usually not too problematic, when associated findings are taken into account along with the pattern of gas (i.e. peripheral in portal venous gas, cent...
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...
Posterior inferior cerebellar artery (PICA) occlusion may cause infarction of any of the vascular territory of the PICA, namely the posterior inferior cerebellum, inferior cerebellar vermis and lateral medulla.
Typically considered the most common territory involved in cerebellar ...
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...
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 spinola...
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 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...
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)
Primary immunodeficiency states are 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)