H-shaped vertebra (also known as Lincoln log vertebra) are a characteristic finding of sharply delimited central endplate depression, classically seen in approximately 10% of patients with sickle-cell anaemia, and results from microvascular endplate infarction (figure 1)3.
It may occasionally b...
H1N1 influenza is a strain of influenza that notably resulted in a pandemic in 2009.
It is type of influenza A virus of swine origin.
There can be a wide spectrum of clinical syndromes with patient's ranging from being asymptomatic to having fulminating viral p...
The habenula is part of the epithalamus and receives input from the brain via the stria medullaris. It outputs to many midbrain areas involved in releasing neuromodulators, such as dopamine, norepinephrine, and serotonin.
The habenula was traditionally divided into lateral (limbic) and medial (...
A habitual miscarriage is the term given when a woman has had more than 3 miscarriages and it affects approximately 1-2% of women.
Many causes are identified.
mullerian duct anomalies
acquired uterine causes
uterine adhesion bands
Haemangiopericytomas of the spleen are a very rare vascular neoplasm with only a few case reports available at the time of writing.
Splenic haemangiopericytomas are typically asymptomatic or can result in splenomegaly.
These are a soft tissue vascular neoplasm...
Haemangioblastomas are tumours of vascular origin and occur both in patients with von Hippel Lindau (vHL) as well as sporadically. They are WHO grade I tumours that can occur in the central nervous system or elsewhere in the body, including kidneys, liver and pancreas.
These tumours generally p...
A haemangioendothelioma is a tumour derived from blood vessels.
Sub types dependent on location include
haemangioendothelioma of liver
This article is intended to be the general article on haemagi...
Haemangiomas are benign tumours of vascular origin usually seen in early childhood, divided into
Unfortunately, the term haemangioma has been widely misused to apply to many non-neoplastic vascular malformations, particularly the com...
Haemangiopericytoma (HPC) is a term formerly used to describe a continuum of mesenchymal tumours with elevated cellularity found throughout the body in soft tissue and bone. As the growth pattern of HPC is shared by numerous unrelated benign and malignant tumours, the term as a group of these tu...
Haemarthosis is haemorrhage into a joint space and can be regarded as a subtype of a joint effusion.
Trauma is by far the most common cause of a haemarthosis. Other causes include bleeding disorders, neurological deficits, arthritis, tumours and vascular damage.
Lipohaemarthrosis is a result o...
Haematocolpos is a term given to a blood filled dilated vagina but without any accompanying blood (often menstrual blood) within the uterine cavity.
Patients may present with amenorrhoea or vague abdominal pain.
imperforate hymen: frequent cause
The haematocrit effect with fluid-fluid levels is the result by layering of heavier cellular elements of blood located dependent to liquid supernatant may be seen on CT or MRI. It is most frequently seen in the setting of anticoagulation therapy or coagulopathy.
signal flare phenomenon
A haematometrium refers to a uterus filled with blood.
pyometrium: uterus filled with pus
haematometrocolpos: uterus and vagina filled with blood
hydrometrium: uterus filled with fluid
Haematometrocolpos refers to a blood filled distended uterus and vagina.
The estimated incidence in teenagers is at ~1 in 1000-2000 5.
imperforate hymen : in ~2/3 of cases
transverse vaginal septum
Haematopoietic stem cell transplantation (HSCT) is a relative common procedure used to treat a wide spectrum of conditions 1,2:
lymphoproliferative disorders, e.g. lymphoma, multiple myeloma (most common indication)
solid tumours, e.g. neuroblastoma, Ewing sarcoma, extragonadal germ...
Abdominal complications of haematopoietic stem cell transplantation can occur early (0-100 days) or late (>100 days) post transplant.
bacterial infections, e.g. pseudomembranous colitis
fungal infections, often affecting the oesophagus or as hepatic/splenic microabsce...
A haematosalpinx refers to intraluminal blood within the Fallopian tube (often dilated).
tubal ectopic pregnancy: common cause 1
endometriosis: common cause 5
pelvic inflammatory disease
fallopian tube torsion
Haematospermia refers to the presence of blood in semen or ejaculatory fluid. It is a symptom that can cause great anxiety to patients despite commonly being of benign aetiology.
urogenital infections including sexually transmitted disease
commonest cause in < 40 years...
Haematuria occurs when blood enters the urinary collecting system. There are many aetiologies for haematuria, and they range from benign and transient to gravely concerning. It can derive from the kidneys, ureters, bladder, prostate (in men), or urethra. Imaging can often be useful to determine ...
Haematuria in a child is evaluated differently than in an adult in two main respects:
there is a lower likelihood of a malignancy (renal or bladder) causing the haematuria
preference is given to nonionizing radiation
Haematuria can be considered in three main forms:
Haemobilia refers to the presence of blood in the biliary tree.
The classical clinical triad, only seen in ~50% of cases, consists of:
melaena (i.e. upper gastrointestinal bleeding)
iatrogenic: surgical or percutaneous pro...
Haemochromatosis is an iron overload disorder characterised by a progressive increase in total body iron stores and deposition of iron in some non-reticuloendothelial system (RES) body organs resulting in some instances in organ dysfunction.
This article focus on general principles of hemochrom...
Cardiac involvement in haemochromatosis typically occurs with primary haemochromatosis, as the organ is usually spared in the secondary form of the disease.
Cardiac involvement occurs in approximately 15-20% of the patients with haemochromatosis.
Pancreatic manifestations of haemochromatosis typically occur with primary haemochromatosis, as the organ is usually spared in the secondary form of the disease.
Iron deposition can occur in the pancreas with primary hemochromatosis. Pancreatic involvement is uncommon in patients wi...
Haemochromatosis is a systemic disease which affects many organs systems (see the main hemochromatosis article), including the joints, characterised by haemosiderin and calcium pyrophosphate deposition resulting in:
chondrocalcinosis: particularly knees and triangular fibrocartilage
An acquired arm arteriovenous fistula (AVF) creation is a procedure performed for haemodialysis access in those with end stage renal failure. It connects and artery to a vein in the vein. This can either be a native connection or a connection using a PTFE (polytetrafluoroethylene) graft.
Haemolytic anaemia is a form of anaemia where red blood cells (RBCs) are destroyed either intravascularly or extravascularly.
The patient presents with anaemia and jaundice. Diagnosis is based on several laboratory parameters 1:
increased unconjugated bi...
Haemolytic disease of the newborn (HDN) results when maternal antibodies attack the fetal red blood cells, leading to a haemolytic anaemia and accumulation of bilirubin in the fetus or newborn. It can affect the newborn to varying degrees of severity. When the condition occurs in utero the term ...
Haemolytic uraemic syndrome (HUS) is a multisystem thrombotic microangiopathic disease characterised by the triad of renal failure, haemolytic anaemia and thrombocytopenia. It is the most common cause of renal failure in infancy and childhood requiring dialysis.
There are two forms of this syn...
Haemopericardium refers to the presence of blood within the pericardial cavity, i.e. a sanguineous pericardial effusion. If enough blood enters the pericardial cavity, then a potentially fatal cardiac tamponade can occur.
There is a very long list of causes 1,4 but some o...
Haemoperitoneum is the presence of blood within the peritoneal cavity.
penetrating or non-penetrating abdominal trauma (often with associated organ injury) 1
ruptured ectopic pregnancy
ovarian cyst rupture
aneurysm or pseudoaneurysm rupture
Haemophagocytic lymphohistiocytosis (HLH) is a nonmalignant disorder of immune regulation characterised by overproduction of cytokines and diminished immune surveillance. It may affect multiple organs.
It typically affects infants and children 5.
The condition can be p...
Haemophilia is an inherited bleeding disorder which is X-linked recessive and therefore occurs almost exclusively in males. There are two subtypes - haemophilia A (80%) and haemophilia B (20%).
The incidence of haemophilia A is around 1 in 5000 male births, and the incidence of h...
Haemophilic arthropathy refers to permanent joint disease occurring in haemophilia sufferers as a long-term consequence of repeated haemarthrosis. Around 50% of patients with haemophilia will develop a severe arthropathy.
Haemophilia is an x-linked recessive disease affecting mal...
Haemophilic pseudotumour is a rare complication of haemophilia consisting of a progressive cystic swelling of muscle and/or bone, occurring in less than 2% of haemophiliacs.
It is reported in 1-2% of haemophiliacs patients.
Most develop in the muscles of the pelvis a...
Haemopneumothorax is a term given when there is concurrent presence of a haemothorax and well as a pneumothorax. It is a variant of a hydropneumothorax.
It is typically seen in the setting of trauma (traumatic haemopneumothorax) but can rarely occur in non-traumatic situations inclu...
Haemoptysis refers to coughing out blood. Generally it appears bright red in colour as opposed to blood from gastrointestinal tract which appears dark red. It is considered an alarming sign of a serious underlying aetiology.
Massive heamoptysis is referred to as expectoration of &g...
A haemorrhagic corpus luteal cyst results from bleeding into a corpus luteal cyst.
Commonly described findings include
complex adnexal mass
adnexal thick walled cystic lesion with lace like strands
adnexal thick walled cystic lesion with low level echoes wi...
Haemorrhagic infarct or haemorrhagic transformation of an infarct is seen to occur secondary to the breakdown of the lamina of the microvessels.
Intracerebral haemorrhage (ICH) may overlap with a haemorrhagic infarct and hence needs to be differentiated as the line of treatment will vary.
Haemorrhagic intracranial metastases are considered to represent between 3-14% of all cerebral metastases (c.f. 1-3% of gliomas are haemorrhagic).
These classically originate from:
melanoma: melanoma metastases to brain
renal cell carcinoma
thyroid carcinoma: papillary carci...
Various types of brain tumours may cause haemorrhage. Increased tumour vascularisation with dilated, thin-walled vessels and tumour necrosis are the most important mechanisms of haemorrhage. The list includes:
choroid plexus carc...
A mnemonic for primary malignancies responsible for haemorrhagic metastases is:
MR CT BB
M: melanoma: metastatic melanoma to brain
R: renal cell carcinoma
T: thyroid carcinoma, teratoma
B: bronchogenic carcinoma
B: breast carcinoma
Haemorrhagic ovarian cysts (HOCs) usually result from haemorrhage into a corpus luteum or other functional cyst. Radiographic features are variable depending on the age of the haemorrhage. They typically resolve within eight weeks.
Patients may present with sudden-onset ...
Haemorrhagic pancreatitis is a possible uncommon complication that can occur with pancreatitis and is characterised by bleeding within or around the pancreas. It is usually considered a late sequela of acute pancreatitis.
Haemorrhage can occur in patients with severe necrotising panc...
Haemorrhagic pulmonary metastases are those which tend to be complicated by pulmonary haemorrhage within them, resulting in characeristic imaging appearances. Metastases of some tumour histologies are more likely to haemorrhage -- knowledge of this can help refine the differential diagnoses.
Haemorrhagic transformation is a complication of cerebral ischaemic infarction and can significantly worsen prognosis.
It should be noted that the term haemorrhagic transformation is a little variably used and collectively refers to two different processes, which have different incidence, appea...
The haemosiderin cap sign refers to an MR imaging feature in some spinal tumours where a cap of T2 hypointense haemosiderin is above and/or below the tumour due to previous haemorrhage.
It is most often associated with spinal cord ependymomas, being seen in 20-33% of these cases 1. The sign ho...
Haemosiderosis is a general term referring to accumulation of haemosiderin, which particularly occurs in the reticuloendothelial system (RES) and does not cause organ damage.
Some causes include:
mainly depositional siderosis in RES
if >40 units transfused...
Haemothorax literally means blood within the chest, is a term usually used to described a pleural effusion due to accumulation of blood. If a haemothorax occurs concurrently with a pneumothorax it is then termed a haemopneumothorax.
A tension heemothorax refers to haemothorax thats result from...
The Haggitt level is a histopathological term used for describing the degree of infiltration from a malignant polypoidal lesion.
Levels of invasion
0: carcinoma in situ or intramucosal carcinoma
1: invasion of the submucosa, but limited to the head of the polyp
2: invasion extending into the...
Haglund deformity, also known as a pump bump or Bauer bump or Mulholland deformity, is defined as bony enlargement formed at posterosuperior aspect of calcaneum. This deformity leads to retrocalcaneal bursitis.
It may result secondary to chronic pressure of rigid shoes.
Haglund syndrome refers to the triad of
insertional achilles tendinopathy
superficial retro tendo Achilles bursitis
This results in pain at the back of the heel. It is associated with calcaneal spurs, and the wearing of high heels (thus the colloquial term "pump...
The hair on end sign refers to a radiographic appearance on a skull which results from a periosteal reaction manifesting as perpendicular trabeculations interspersed by radiolucent marrow hyperplasia along the skull vault. It is classically described with plain skull radiographs although can als...
The so-called hairy pleural plaque, are a manifestation of asbestos related disease. They arises from the visceral pleura, typically from an interlobar fissure. The hairiness stems from short radially oriented linear regions of fibrosis extending from the plaque into the adjacent lung parenchyma...
Hajdu-Cheney syndrome, was first described as cranioskeletal dysplasia 1 in 1948. It is a very rare connective tissue disorder with only 50 cases reported in the literature 2.
It is mostly diagnosed in adulthood or adolescence with the presence of a positive family histor...
Physical half life time (Tp)
The time interval required for an amount of certain radioactive nuclei to decay to its half of original value.
Biological half life time (Tb)
The time interval required for the body to eliminate 50% of any substance by normal routes of elimination: metabolic turn...
Half value layer (HVL) is the width of a material required to reduce the air kerma of a x-ray or gamma-ray to half its original value. This applies for narrow beam geometry only as broad-beam geometry will experience a large degree of scatter, which will underestimate the degree of attenuation. ...
Halitosis refers to the symptom of foul oral odour, commonly termed "bad breath", that patients can present with, usually to dental services.
It is thought to be caused by the presence of volatile sulphur compounds that are produced by bacteria. Although the underlying caus...
Haller cells are also known as infraorbital ethmoidal air cells or maxilloethmoidal cells. They are extramural ethmoidal air cells that extend into the inferomedial orbital floor and are present in ~20% (range 2-45%) of patients, depending on their exact definition 1-3.
In most instances they a...
Hallervorden-Spatz syndrome, now known as pantothenate kinase-associated neurodegeneration (PKAN), is an autosomal recessive disorder causing involuntary spasticity and progressive dementia. It is a subset of neurodegeneration with brain iron accumulation (NBIA).
Hallux rigidus (osteoarthrosis with restricted motion) is the second most common disabling deformity of the first metatarsophalangeal joint after hallux valgus.
It is most commonly seen in middle-aged patients, but can develop during adolescence. Unlike a hallux valgus, males appe...
The hallux sesamoid bones are paired, dual ossicles of the foot. They function as a fulcrum to increase the leverage of both flexor hallucis brevis and longus.
The hallux sesamoids are ovoid-shaped ossicles. There is a medial (tibial) and lateral (fibular) hallux sesamoid and ar...
A hallux valgus is fixed abduction of the first metatarsophalangeal joint of the great toe. It is usually due to metatarsus primus varus which is medial deviation or adduction of the first metatarsal with an increased first-second metatarsal angle.
Halo sign in mammography refers to a radiolucent rim (halo) around a lesion and is generally but not always indicative of a benign breast lesion. Exceptions include intracystic carcinoma, papillary carcinoma, and carcinoma arising within a fibroadenoma.
halo sign (chest)
halo sign (u...
The halo sign (HS) in chest imaging is a feature seen on lung window settings (typically HRCT), ground glass opacity surrounding a pulmonary nodule or mass and represents haemorrhage. It is typically seen in angioinvasive aspergillosis.
Histopathologically, it represents a focus of p...
The hamate is one of the carpal bones, forms part of the distal carpal row and has a characteristic hook on its volar surface.
The hamate has a wedge-shaped body. It bears an uncinate (unciform) hamulus (hook of hamate) which projects in a volar fashion from the dista...
Hamatolunate impingement is an uncommon cause of ulnar-sided wrist pain. The condition occurs most commonly in wrists where there is type II lunate morphology (existence of a medial facet on the distal lunate for articulation with the hamate). Repeated impaction of the opposing articular surface...
Hamburg classification system of vascular malformations is one of the more commonly used systems to describe the wide range of vascular malformations, largely replacing the many various eponymous syndromes traditionally used. It accounts for the underlying anatomical, histological, and pathophys...
Hamman syndrome, (or Macklin syndrome), refers to spontaneous pneumomediastinum along with subcutaneous emphysema.
It is a rare entity most often encountered in young adults. It is a known entity peri- and postpartum 3.
The condition is most commonly asympt...
Hampton hump refers to a dome-shaped, pleural-based opacification in the lung most commonly due to pulmonary embolism and lung infarction (it can also result from other causes of pulmonary infarction (e.g. vascular occlusion due to angioinvasive aspergillosis). While a pulmonary artery embolism ...
The Hampton line is a thin millimetric radiolucent line seen at the neck of a gastric ulcer in barium studies (profile view), indicating its benign nature. It is caused by a thin line of mucosa overhanging the ulcer's crater.
The hamstrings are the muscles of the posterior thigh and include the:
lateral: biceps femoris
medial: semimembranosus and semitendinosus
Apart from the short head of biceps femoris, the muscles share two common features:
span both the hip and knee joints and therefore produce hip extension ...
All the intrinsic muscles of the hand are innervated by the ulnar nerve, except 4 muscles which are supplied by the median nerve and are easily recalled with the mnemonic FOAL:
F: flexor pollicis brevis
O: opponens pollicis
A: abductor pollicis brevis
L: lateral 2 lumbricals
Hand radiographs are commonplace in the Emergency Department or the trauma reporting list.
Review the wrist
A hand radiograph contains a PA and oblique view of the distal radius and ulna and the carpus.
check the wrist as you would for a wrist radiograph (an approach)
The hand series is comprised of a posteroanterior and oblique, projection although additional radiographs can be taken for specific indications.
The series primarily examines the metacarpals,phalanges along with the carpal bones that are consisting of the scaphoid, lunate, triquetrum, pisiform,...
Hand-foot-and-mouth disease occurs in children as a result of viral infection and results in vesicular erruption on the hands and feet as well as ulcers of the oral mucosa.
It can occur following infection with a wide variety of viruses, but by far the most cases are the result of infection wit...
The Nørgaard projection is also known as ball-catcher view or posterior oblique view of both hands. It is an additional projection of the routine hand series. The ball catcher view is often done to investigate signs of rheumatoid arthritis.
patient may be seated alongside or ...
The bilateral PA view often compliments the ball-catcher view,. It is often done to investigate signs of rheumatoid arthritis.
patient may be seated alongside or facing the table
both hands are pronated with their palmer surfaces placed on the detector
The lateral hand view is an orthogonal view taken along with the PA view of the hand. Often an additional projection, the lateral view is used primarily to assess for foreign bodies and/or displacement of fractures/dislocations.
patient is seated alongside the table
hand is e...
The Hand oblique view is part of a two view series metacarpals, phalanges, carpal bones and distal radial ulnar joint.
patient is seated alongside the table
the affected arm if possible is flexed at 90° so the arm and hand can rest on the table
the hand is rotated externall...
The Hand PA view is part of a two view series metacarpals, phalanges, carpal bones and distal radial ulnar joint.
patient is seated alongside the table
the affected arm if possible is flexed at 90° so the arm and hand can rest on the table
the affected hand is placed, palm ...
The hand is part of the upper limb below the forearm and wrist. In the supinated anatomical position, the palm is facing anteriorly. The bones of the hand are:
Hanging noose sign in obstretric imaging is a rarely described but classical finding of a true umbilical cord knot. It demonstrates a transverse section of the umbilical cord surrounded by a loop of umbilical cord and changes in the pressure of the knot can be demonstrated with the fetus movemen...
Hangman fracture, also known as traumatic spondylolisthesis of the axis, is a fracture which involves the pars interarticularis of C2 on both sides, and is a result of hyperextension and distraction.
Post-traumatic neck pain after a high-velocity hyperextension injury is ...
A hard metal pneumoconiosis is usually classified as a type of fibrotic pneumoconiosis where the precipitating agent consists of a hard metal (not a heavy metal) such as.
tungsten / tungsten carbide alloys
or a mixture
A more broader term used is hard metal lung disease (...
The harlequin eye deformity may seen in unilateral (plagiocephaly) or bilateral (brachycephaly) coronal suture synostosis, and refers to the elevation of the superolateral corner of the orbit.
Harmonic imaging is a technique in ultrasonography that provides images of better quality as compared with conventional ultrasound technique.
Harmonic imaging exploits non-linear propagation of ultrasound through the body tissues. The high pressure portion of the wave travels faster th...
The Harris projection (also called the penetrated axial projection) is a special radiographic view that is used for assessment of talocalcaneal coalition.
The patient stands on the cassette and the x-ray beam is angled between 35 and 45 degrees.
Harrison's sulcus refers to a groove at the lower end of the rib cage seen in young children / infants with abnormally weak bones (e.g. rickets) or chronic respiratory disease (e.g. severe asthma). The lower chest is drawn in with flaring of the rib margin. The exact cause is controversial altho...
Hashimoto thyroiditis, also known as lymphocytic thyroiditis or chronic autoimmune thyroiditis, is a subtype of autoimmune thyroiditis. It is one of the most common thyroid disorders.
Typically affects middle aged females (30-50 year age group with a F:M ratio of 10-15:1).
Hatchet sign refers to the limited erosion of the lateral aspect of humeral head that produces a hatchet shaped deformity. This finding is typically associated with ankylosing spondylitis.
In the absence of osteoporosis and presence of sclerosis this sign helps to differentiate it from rheumat...
The haustral folds represent folds of mucosa within the colon. They are formed by circumferential contraction of the inner muscular layer of the colon.
The outer longitudinal muscular layer is organised into three bands (taeniae coli) which run from the caecum to the rectum. These muscular band...
Haustral markings are the radiological appearance of the haustral folds within the colon. Disappearance of the haustral folds results in the lead pipe appearance of ulcerative colitis.