A Herbert screw is an instrument is used in internal fixation of unstable scaphoid fracture. It is a headless screw with thread along its entire length. The two halves of the screw have a different pitch though, which causes compression of the fracture.
Unstable scaphoid fractures ...
Despite the vast majority of renal cancers being sporadic, there are a number of hereditary renal cancer syndromes:
von Hippel Lindau syndrome: predominantly clear cell type
tuberous sclerosis: predominantly clear cell type (also associated with angiomyolipoma)
Heterogeneous echogenicity of the thyroid gland is a non-specific finding and is associated with conditions diffusely affecting the thyroid gland. These include:
The words heterogeneous and heterogenous, and their antonyms homogeneous and homogenous respectively, are commonly used in radiology reports and medical literature. There is a seemingly widely held misconception that they represent alternative spellings of the same word, possibly with heterogene...
Hibb angle has been used to identify the apex of deformity in patients with pes cavus on lateral weight bearing radiograph. Hibb angle is formed by the lines running along the axes of the calcaneus and the first metatarsal. The intersection of the lines represents apex of the deformity.
Hiccups (or hiccoughs), medical term singultus (rarely used), are an unpleasant phenomenon, experienced by everyone on occasion, and usually self-limiting. However the much rarer intractable chronic form can be extremely debilitating.
Hiccups are a symptom that has probably been e...
High arched palates are a facial feature of many syndromes, although the classic association is Marfan syndrome. There are hundreds of conditions associated with high arched palates, with some of the radiologically-more important including:
High attenuation lymphadenopathy has been described with:
Kaposi sarcoma 1,6
angioimmunoblastic lymphadenopathy (AILD)
Kimura disease (due to nodal hemorrhage) 6
metastatic hypernephroma (presumed due to nodal hemorrhage) 6
If there is calcification associated...
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 orthopedic 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 treatme...
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 tumors:
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, etiology 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 favor 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.
Hydronephrosis in fetuses and newborns has specific causes that are covered in a separate article.
The term hydroureteronephrosis (or hydronephr...
Hydroxyapatite crystal deposition disease (HADD) is a disease of uncertain etiology characterized 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 hemorrhage, calcium, or highly cellular tumors.
There is overlap between the entities, with some cerebral metastases appearing in more than one list 1-6:
hemorrhagic cerebral metastases (mnemonic)
Hyperattenuating paranasal sinus opacification can arise in a number of situations:
fungal sinus disease
acute hemorrhage into sinus (hemosinus)
In some situations can consider early calcification within the sinus - intrasinus calcification.
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 ade...
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 anemia
hyperostosis frontalis interna
long-term phenytoin use
Hyper-reninaemic hypertension may have many causes including:
renal artery stenosis
renal secreting tumor, e.g. renal cell carcinoma, reninoma
renal compression: large renal mass, subcapsular hemorrhage (Page kidney)
Hypertrophic osteoarthropathy is a syndrome characterized 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 tumors 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 in 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 characterized 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-ischemic encephalopathy in adults and older children (i.e. not neonates), also known as global hypoxic-ischemic injury, is seen in many settings and often has devastating neurological sequelae.
For a discussion of neonatal hypoxia, refer to neonatal hypoxic-ischemic 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 characterized 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 tumor 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 an 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 generalized acceleration in bone maturation can result from a number of etiological 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 edema
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 - pediatric
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 pediatric population.
The brachiocephalic or innominate artery usually takes its origin to the left of the trachea. T...
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...
Interstitial lung disease (ILD) is an umbrella term that encompasses a large number of disorders that are characterized by diffuse cellular infiltrates in a periacinar location. The spectrum of conditions included is broad, ranging from occasional self-limited inflammatory processes to severe de...
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 a non-specific finding seen in numerous conditions.
It may be observed in pediatric 5 as well as adult populations.
degenerative: relatively common and may occur in up to 6% of 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 diarrhea, 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 ...
Intracholecystic papillary neoplasms (ICPN), also referred to as intracholecystic papillary-tubular neoplasms, are rare recently described pre-invasive neoplasms of the gallbladder.
On imaging, these lesions resemble adenomas of the gallbladder or have features suspicious for gallbladder carcin...
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 leukemia
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 edema
intracranial epidermoid cyst
lesions with variable or moderately high signal
primary central nervou...
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 tumors exhibit different forms of calcification. Some lesions commonly show calcification while in some tumors, calcification is seen only in few number of cases. In this article these tumors are classified on the basis of frequency of calcification.
Intraductal neoplasms of the bile ducts are basically divided in those lesions that are a precursor to adenocarcinoma of the bile ducts, also referred to as preinvasive lesions, and the invasive tumors, which are made basically by cholangiocarcinomas of intraductal growing type.
Intraductal papillary neoplasm of the bile duct (IPNB) is a pre-invasive biliary tree neoplasm considered to be a precursor of cholangiocarcinoma.
Biliary papillary adenoma and noninvasive papillary carcinoma of the biliary tract were terms used to refer to localized low-grade and...
Intraductal tubulopapillary neoplasms of the bile ducts are rare intraluminal mass forming pre-invasive biliary neoplasms with no mucin production.
ITPNs of the bile ducts are rare tumors of unknown incidence, found more frequently in women at their 60s 1,2.
Intradural extramedullary neoplasms are located outside the spinal cord but within the dural sheath.
The majority (70-80%) of spinal canal tumors are intradural extramedullary 1.
Patients present with signs and symptoms of spinal cord or nerve root compres...
Intralaminar dural hematomas in the intracranial space, are exceedingly rare, and represent hemorrhage between the two layers of the dura. As a result it has distinctive features allowing it to be distinguished from extradural hematomas, but mimics subdural hematomas. They are equivalent to epid...
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 tumors and some extracranial tumors 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 c...
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 tumor types arise from, or can bulge into the ventricular system, although there are certain lesions that are relatively r...
Ionic cerebral edema is a form of cerebral edema usually associated with cytotoxic edema, and represents the passage of water and sodium from capillaries into the brain parenchymal extracellular space. It is distinguished from vasogenic edema as the blood brain barrier (BBB) remains intact and t...
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 esophagectomy, an upper gastrointestinal tract operation performed for mid and distal esophageal pathology, usually esophageal cancer.
Due to the necessity of removing a significant length of the esophagus, the stomach is "pull...
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 tumors 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 orthopedic 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 bon...