A high bone mineral density is one where the bone mineral density is usually above two standard deviations above what is expected for age. This can sometimes be seen on routine Dexa scan assessment. Some authors advocate advocated a definition of a high BMD where the Z-score is >+2.5 to highligh...
High output cardiac failure refers to a state of cardiac failure that is associated with a higher than normal cardiac output which is still not sufficient for body tissue demands.
Patients can present with a number of symptoms of varying degrees which include tachycardia,...
A high-riding shoulder refers to the superior displacement/subluxation of the humeral head with resultant decrease in the acromiohumeral distance.
The differential for a high-riding shoulder is:
rotator cuff tear with or without rotator cuff arthropathy
The term high-risk breast lesion is given to a breast lesion that carries an increased risk for the future development of breast cancer or carries suspicion of a more sinister pathology around or in association with the lesion. The term has some overlap with borderline breast disease. Many radio...
Hip hemiarthroplasty is an orthopaedic procedure for the treatment of certain femoral neck fractures where the femoral head is removed and replaced. The prosthetic head articulates with the native acetabulum hence it is designated as 'hemi'.
Hemiarthroplasty is indicated for the surgical treatm...
Cardiovascular manifestations are seen with increased frequency in the HIV/AIDS adult population, and include:
dilated cardiomyopathy (prevalence 8-30%)
endocarditis: either infective or non-bacterial thrombotic (marantic) which is associated with malignancy or HIV wasti...
The CNS manifestations of HIV/AIDS (neuroAIDS) occur secondary to a wide range of neurodegenerative, infectious, inflammatory, or neoplastic processes.
Since the introduction of highly active antiretroviral therapy (HAART) in 1996, there has been a shift in the epidemiology of CN...
Gastrointestinal manifestations of AIDS are protean and can be broadly divided into opportunistic infections and tumours:
herpes simplex virus (HSV)
primary infection with HIV
Genitourinary manifestations of HIV/AIDS are protean and can be divided into:
renal diseases related to opportunistic infections: CMV, tuberculosis and MAC infections, fungal infections, pneumocystis carinii infection
drug-related renal diseases:
Musculoskeletal manifestations of HIV/AIDS are not as common as CNS or pulmonary complications. Nonetheless, their prevalence is high.
Depending on the condition, aetiology may be related to the HIV infection itself, the resultant immunodeficiency, or antiretroviral therapy (HAART).
HIV-associated neoplasms are numerous and can be broadly divided into two groups:
associated but not AIDS defining malignancies
The development of these malignancies in HIV affected individuals generally implies progression to AIDS 4:
Hodgkin lymphoma (HL) commonly involves the musculoskeletal system, being radiographically evident in 10-25% of cases at some point during the disease course. The majority of early bone lesions are lytic, however, blastic lesions are common (up to 45%).
Osseous involvement may occur...
Hounsfield unit average calculation (HUAC) is an imaging marker of sarcopenia, a key component of frailty 1. Psoas muscle assessment at L4 level is typically performed 1.
Sarcopenia has been associated with poor outcomes in trauma, oncology and surgical cases.
HUAC has been proposed as a novel...
Humeral avulsion of the glenohumeral ligament (HAGL) is, as the name suggests, avulsion of the inferior glenohumeral ligament (IGHL) from its humeral insertion. It can be associated with a bony avulsion fracture in which case it is referred to as bony humeral avulsion of the glenohumeral ligamen...
Accurately determining whether hydrocephalus or atrophy (compensatory enlargement of the CSF spaces) is the cause of ventriculomegaly can be, at times, challenging in image interpretation.
Features that favour hydrocephalus include:
dilatation of the temporal horns
Hydronephrosis is defined as dilatation of the urinary collecting system of the kidney (the calyces, the infundibula, and the pelvis) 1. The term hydroureteronephrosis (or hydronephroureterosis) is used when the dilatation also involves the ureter.
Hydronephrosis in fetuses and newborns has sp...
Hydropneumothorax is a term given to the concurrent presence of a pneumothorax as well as a hydrothorax (i.e. air and fluid) in the pleural space.
It may arise in various situations which include
Hydroxyapatite crystal deposition disease (HADD) is a disease of uncertain aetiology characterised by periarticular and intra-articular deposition of hydroxyapatite (HA) crystals.
The shoulder is the most frequently involved site with classic calcific tendinitis presentation.
Hyperattenuating cerebral metastases on CT can be due to haemorrhage, calcium, or highly cellular tumours.
There is overlap between the entities, with some cerebral metastases appearing in more than one list 1-6:
haemorrhagic cerebral metastases (mnemonic)
Hyperattenuating paranasal sinus opacification can arise in a number of situations:
fungal sinus disease
acute haemorrhage into sinus (haemosinus)
In some situations can consider early calcification within the sinus.
Hyperattenuating pulmonary abnormalities can result from a variety of processes and have varied radiographic appearances. It is easiest, for the purposes of radiology, to divide them into:
hyperdense linear or reticular opacities
hyperdense pulmonary nodules
hyperdense pulmonary mass
There are only a few causes of a pulmonary mass with internal calcification. They include:
granuloma: most common
mucoid calcification of mucinous adenocarcinoma:
gastrointestinal tract ad...
Hyperdense pulmonary nodules are a subset of pulmonary nodules that have relatively increased attenuation, usually caused by calcification within the nodule. Here, we broadly refer to a nodule as a pulmonary opacity <30 mm.
calcified pulmonary nodules are a specific grou...
There are a number of lesions that appear hyperechoic on ultrasound. Such lesions can be either completely or partly hyperechoic and include both benign and malignant entities.
fat containing breast lesions
lipoma of the breast
fibroadenolipoma (hamartoma) of the breast
Hyperostosis of the skull has many causes, broadly divided into focal or diffuse.
Paget's disease of bone
metastatic disease, especially prostate carcinoma
chronic, severe anaemia
hyperostosis frontalis interna
long-term phenytoin use...
Hyper-reninaemic hypertension may have many causes including:
renal artery stenosis
renal secreting tumour, e.g. renal cell carcinoma, reninoma
renal compression: large renal mass, subcapsular haemorrhage (Page kidney)
Hypertrophic osteoarthropathy is a syndrome characterised by periosteal reaction of the long bones without underlying bone lesion. There are a broad range of manifestations, although typically there is symmetrical involvement of the appendicular skeleton. Accompanying abnormal soft tissue prolif...
Hypertrophy of the caudate lobe is seen in a number of conditions, including:
cirrhosis: most common
primary sclerosing cholangitis (end stage)
congenital hepatic fibrosis
cavernous transformation of the portal vein
The caudate-right lobe ratio m...
There are several tumours which are noted to cause hypervascular metastases. The list of differential diagnoses includes:
renal cell carcinoma (RCC)
breast cancer: homogeneously hypervascular liver metastases from breast are considered rare 3
Hypoglobus refers to the inferior displacement of the globe into the orbit. It may or may not be associated with enophthalmos.
Hypoglobus is most commonly caused by fracture of the orbital floor but may be due to other causes:
silent sinus syndrome
orbital foreign bodies
Hypomyelinating disorders are a heterogeneous subset of white matter disorders characterised by abnormally low amounts of myelination.
In distinction to other myelin disorders, hypomyelination is a permanent deficiency in myelin deposition rather than myelin destruction (i.e. demyelination) or ...
Hypotelorism refers to an abnormal decrease in distance between any two organs although some authors use the term synonymously with orbital hypotelorism meaning an abnormal decrease in the distance between the two eyes (the eyes appear too close together). The article mainly focuses on the latte...
Hypothalamic lesions are numerous representing some entities that are unique to the hypothalamus, as well as many lesions that can be seen elsewhere within the brain. Additionally, due to its proximity to the optic chiasm, third ventricle and pituitary region, many lesions of these locations can...
Hypoxic-ischaemic encephalopathy in adults and older children (i.e. not neonates), also known as global hypoxic-ischaemic injury, is seen in many settings and often has devastating neurological sequelae.
For a discussion of neonatal hypoxia, refer to neonatal hypoxic-ischaemic encephalopathy.
Idiopathic interstitial pneumonias (IIPs) are diffuse interstitial lung diseases of unknown cause. They are characterized by cellular infiltration of the interstitial compartment of the lung with varying degrees of inflammation and fibrosis.
For many years many attempts have bee...
IgG4-related disease (IgG4-RD) is a systemic disease that is characterised by extensive IgG4-positive plasma cells and T-lymphocyte infiltration of various organs.
This condition has been known by many other names in the past, such as IgG4-related sclerosing disease, IgG4-related s...
Iliac vein occlusion can be due to the variety of causes including:
catheter dissection injuries
IVC filter insertion
direct tumour invasion
enlarged lymph nodes
Gunshot injuries often require imaging assessment, and this evaluation has both clinical relevance (assessment of organ damage, surgical planning and prognostication), and often also forensic implications.
Incidence of gunshot injuries to the head is increasing in some countries, ...
Implantable loop recorders, also known as insertable cardiac monitors, are small insertable devices that continuously monitor and record cardiac rhythms. They are placed subcutaneously and used for the evaluation of patients with recurrent unexplained episodes of palpitations or syncope. They sh...
The incomplete border sign is useful to depict an extrapulmonary mass on chest radiograph.
An extrapulmonary mass will often have a inner well-defined border and an ill-defined outer margin 1-3. This can be attributed to the inner margin being tangential to the x-ray beam and has good inherent ...
A generalised acceleration in bone maturation can result from a number of aetiological factors. They include:
idiopathic isosexual precocious puberty
hypothalamic or parathalamic lesion with sexual precocity: e.g.
A mnemonic that can be used to remember the causes of increased heel pad thickness is:
D: phenytoin therapy
P: peripheral oedema
Increased renal echogencity is a nonspecific finding but can represent a number of underlying conditions.
chronic kidney disease: increased cortical echogenicity
sickle cell disease 4
echogenic renal pyramids - paediatric
Infertility is common, affecting 15-20% of couples, and is defined as the inability to conceive after one year of unprotected intercourse in the fertile phase of the menstrual cycle 3. It can be due to a variety of both female and male factors, and these are discussed in separate articles:
It is important to have a systematic way of approaching a case with subfertility in the exam.
Ultrasound is the initial examination of choice. 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 or HS...
Ingested bones that become lodged in the throat or gastrointestinal tract are a common presentation to the emergency department. Recognition is important because these cases can be potentially fatal.
Patients may present with a 'foreign body' feeling in the throat after eating fish ...
Ingested foreign bodies in children are common as the world is a curious place to young children, who will put anything and everything into their mouth, and will often inadvertently swallow.
The usual practice is for plain films of the chest/abdomen to identify a foreign body.
Innominate artery compression syndrome, also known as brachiocephalic artery compression syndrome, is a rare cause of tracheal stenosis that occurs in the paediatric population.
It can only occur in the presence of an aberrantly positioned thymus that forces the aortic arch or innomi...
Internal hernias due to gastric bypass surgery are more common after laparoscopic gastric bypass than after an open procedure.
It is a particularly sinister complication with variable, nonspecific clinical presentations. Most patients report a combination of postprandial...
Diffuse interstitial lung disease encompasses a large number of disorders that are characterised by cellular infiltrates in a periacinar location. While some disease processes may cause significant injury to the underlying lung parenchyma (e.g. usual interstitial pneumonia), some do not (e.g. pu...
An interstitial lung pattern is a regular descriptive term used when reporting a plain chest radiograph. It is the result of the age-old attempt to make the distinction between an interstitial and airspace (alveolar) process to narrow the differential diagnosis.
A re-read of the timeless work o...
Intervertebral disc calcification is seen with numerous conditions.
It may be observed in paediatric 5 as well as adult populations.
degenerative: relatively common and may occur in up to 6% in routine abdominal radiographs in adults
Intestinal failure is when a patient's native bowel is unable to digest and absorb the food, electrolytes and fluids needed for normal growth and development.
This often includes intractable diarrhoea, weight loss, dehydration, electrolyte imbalance, and malnutrition.
Intestinal nonrotation is a congenital anomaly of the intestines that results in the small bowel occupying the right side of the peritoneal cavity and the colon predominantly on the left.
It is sometimes thought of as a subtype of intestinal malrotation.
Nonrotation is estimated ...
Intestinal transplantation is a surgical treatment for intestinal failure. It is one of the most rarely performed transplant procedures performed, exclusively involving the transplantation of donor small bowel to a recipient, with an ileostomy formation.
Due to the high risk of complications w...
Intra-abdominal calcification is common and the causes may be classified into four broad groups based on morphology:
These are discrete precipitates in a vessel or organ. They are sharp in outline but the density and shape vary but in some cases they may be virtually pathognomonic:...
Intra-abdominal calcification in a neonate can be caused by a number of pathologies that cause calcification within the peritoneal space or within organs.
The commonest cause is meconium peritonitis which is the result of aseptic peritonitis secondary...
Intraconal orbital lesions are broadly divided into two main groups; those with or without involvement of the optic nerves:
Lesions with optic nerve involvement:
optic nerve glioma
optic nerve meningioma
lymphoma and leukaemia
Intracranial arterial beading represents alternating areas of constriction in the intracranial arteries that gives the appearance of beads strung together.
The various conditions where this is seen are:
cerebral vasospasm post sub...
Intracranial lesions or processes can be described according to which intracranial compartment they occur within.
The simplest division is into 3 compartments:
extra-axial: external to the brain parenchyma
intra-axial: within the brain parenchyma
intraventricular: within the ventricular sys...
Intracranial cystic lesions in the perinatal period can carry a relatively wide differential which includes:
Supratentorial cystic lesions
choroid plexus cyst
Following lesions may show high signal on diffusion weighted imaging:
lesions with intense high signal
cytotoxic cerebral oedema
intracranial epidermoid cyst
lesions with variable or moderately high signal
primary central nerv...
Intracranial metastases from non-CNS primary neoplasms are becoming more common due to significant advances in cancer treatment over the last few decades. Increasing numbers of patients live longer and present with metastasis in locations considered unusual previously:
brain (parenchymal) metas...
A variety of intracranial tumours exhibit different forms of calcification. Some lesions commonly show calcification while in some tumours, calcification is seen only in few number of cases. In this article these tumours are classified on the basis of frequency of calcification.
Intradural extramedullary neoplasms are located outside the spinal cord but within the dural sheath.
The most common presenting symptoms include weakness, back pain and radicular pain.
Schwannomas are the most common intradural extramedullary spinal lesions (...
Intralaminar dural haematomas in the intracranial space, are exceedingly rare, and represent haemorrhage between the two layers of the dura. As a result it has distinctive features allowing it to be distinguished from extradural haematomas, but mimics subdural haematomas. They are equivalent to ...
Intramedullary spinal metastases are rare, occurring in ~1% of autopsied cancer patients, and are less common than leptomeningeal metastases.
Intramedullary lesions may result from:
growth along the Virchow-Robin spaces
direct extension from leptomeninges
Intrasinus calcification is phenomenon whereby calcification is formed within the paranasal sinuses. It can occur to varying extent and lead to varying degrees of attenuation on CT. Such calcification may occur either concurrently within an opacified sinus or in an aerated sinus, depending on th...
Intrauterine contraceptive devices (IUCD) are one of the most frequently used methods of contraception throughout the world. It prevents pregnancy by:
thinning the endometrial lining
preventing sperm motility
There are two main types of IUCDs:
non-hormonal metallic (...
Intraventricular metastases are a very rare finding. A few intracranial tumours and some extracranial tumours metastasize to the ventricles. The most common site of intraventricular metastasis is the trigone of the lateral ventricles due to high vascularity of the choroid plexuses. The next most...
Intraventricular neoplasms are rare and arise from periventricular structures such as the walls of the ventricular system, the septum pellucidum and the choroid plexus. Many tumour types arise from, or can bulge into the ventricular system, although there are certain lesions that are relatively ...
Ionic cerebral oedema is a form of cerebral oedema usually associated with cytotoxic oedema, and represents the passage of water and sodium from capillaries into the brain parenchymal extracellular space. It is distinguished from vasogenic oedema as the blood brain barrier (BBB) remains intact a...
IUCD (Intrauterine contraceptive device) related uterine perforations are one of the causes of uterine perforation. It is rare, but a serious complication of an IUCD insertion, and is often clinically silent.
The incidence rate is reported at ~2 in 1000 2.
Ivor Lewis procedure (also known as a gastric pull-up) is a type of oesophagectomy, an upper gastrointestinal tract operation performed for mid and distal oesophageal pathology, usually oesophageal cancer.
Due to the necessity of removing a significant length of the oesophagus, the stomach is "...
Joint ankylosis has a relatively broad differential including 1-5:
chronic reactive arthritis
juvenile idiopathic arthritis
A joint effusion is defined as an increased amount of fluid within the synovial compartment of a joint.
There is normally only a small amount of physiological intra-articular fluid. Abnormal fluid accumulation can result from inflammation, infection (i.e. pus) or trauma and may be an exudate, t...
A J-shaped sella is a variant morphology of the sella turcica, whereby the tuberculum sellae is flattened, thus forming the straight edge of the "J". The dorsum sellae remains rounded and forms the loop of the "J".
Differential diagnosis for a J-shaped sella includes 1,2...
Jugular fossa masses comprise a range of pathological lesions that arise from or extend into the jugular fossa in the skull base. Although not a common location for tumours it is not unusual for jugular fossa lesions to be discovered incidentally on cross sectional imaging.
Juvenile osteoporosis refers to osteoporosis occurring in children.
It can arise from a number of causes 1-4:
osteoporosis pseudoglioma syndrome
Kim lesions are superficial tears between the posterior glenoid labrum and glenoid articular cartilage without labral detachment. Failure to identify and treat this lesion may lead to permanent posterior instability.
It typically results from a postero-inferiorly directed force on t...
Klaus height index is the distance between tip of the dens and the tuberculum torcula line (Twining's line). A normal height is 40-41mm.
A decreased Klaus height index is seen in basilar invagination.
K wires (Kirschner wires) are a type of stabilization wire/pin used in orthopaedic surgery. They are pointed stainless steel wires that can be used in multiple roles during internal fixation:
as a temporary measure before more definitive fixation
thin wires are especially useful for smaller bo...
Lacrimal gland masses can be classified into two broad groups - inflammatory (~50%) and neoplastic, either lymphoma (25%) or salivary gland type tumours (~25%).
affects ~25% of patients with systemic disease
orbital inflammatory pseudotumour
A large for date uterus is a clinical observation based on uterine fundal height, which may result in referral for ultrasound assessment, usually in mid to late pregnancy.
constitutionally large fetus
Large joint dislocation is a not uncommon presentation to emergency rooms. Described in order of comonality:
posterior dislocation of the hip
When a pleural effusion is large and unilateral, concern for an underlying abnormality should be raised. Causes include:
primary effusion lymphoma
Laryngeal cysts can occur in any part of the larynx, but are more frequent in supraglottic locations, such as the epiglottis and vallecula. The prevalence of each location varies on different studies.
The laryngeal cysts represent a rare group, about 5%, of benign laryngeal lesio...
Lateral epicondyle fractures are rare epicondylar fractures. They are much rarer than medial epicondyle fractures and represent avulsion of the lateral epicondyle. They are usually seen in the setting of other injuries 1-3.
Incidence typically peaks in the paediatric age group (6...
Leadless cardiac pacemakers are a recently introduced type of cardiac conduction device. These pacemakers are self-contained right ventricular single-chamber pacemakers that are implanted percutaneously via a femoral approach 1-3. There are currently two leadless cardiac pacemakers on the market...
Lead poisoning or plumbism can present with characteristic skeletal features.
This condition usually occurs as a consequence of a toxic environment: prolonged ingestion or inhalation of lead-containing material (e.g. contaminated water, paints, batteries).
The left atrial (LA) line monitors LA pressure and is indicative of left ventricular function, preload and afterload. The LA line enters from the left superior vein and exits the far side of the chest.
The LA line is a single lumen catheter unlike the right atrial line, which is double lumen. N...
When a central venous catheter that is supposed to project over the superior vena cava is abnormally located to the left of the mediastinum a limited differential of left paramediastinal catheter position should be considered 1:
located within a vein
left sided superior vena cava
Left upper lobe collapse has distinctive features but can be challenging to identify on chest radiographs by the uninitiated.
For a general discussion refer to the article on lobar collapse.
The left upper lobe collapses anteriorly becoming a thin sheet...