Acute respiratory distress syndrome (ARDS) is a form of acute lung injury and occurs as a result of a severe pulmonary injury that causes alveolar damage heterogeneously throughout the lung. It can either result from a direct pulmonary source or as a response to systemic injury.
Acute right heart syndrome (ARHS) is defined as a sudden deterioration in right ventricular (RV) function and failure of the RV to deliver adequate blood flow to the pulmonary circulation. This can result in systemic hypoperfusion.
ARHS can occur in several settings 1
in the setting...
Acute sinusitis (rare plural: sinusitides) is an acute inflammation of the paranasal sinus mucosa that lasts less than four weeks and can occur in any of the paranasal sinuses. If the nasal cavity mucosa is also involved then the term rhinosinusitis may be used.
Acute spinal cord ischemia syndrome is uncommon, but usually presents with profound neurological signs and symptoms, and the prognosis is poor.
Acute spinal cord ischemia syndrome represents only 5-8% of acute myelopathies 4,5 and <1% of all strokes 7. The demographic of affected...
Useful mnemonics to remember the symptoms of acute stroke are:
F = face (look uneven?)
A = arm (drift down?)
S = speech (sound strange or difficulty speaking)
T = time (brain cells die every second)
B = balance (sudden loss of balance)
E = eye (sudd...
Acute tubular necrosis is a common type of acute kidney injury, particularly in hospitalized patients.
Acute tubular necrosis is characterized by renal tubular cell damage and death and is usually caused by ischemic or nephrotoxic insults. Deposition of cellular debris within the tu...
Acute unilateral airspace opacification is a subset of the differential diagnosis for airspace opacification.
The exhaustive list of all possible causes would be huge, but a useful framework includes:
pus, i.e. pulmonary infection
Differentiating between acute and chronic infarction on a CT brain is an important skill for many health professionals particularly in the emergency setting:
acute: cytotoxic edema
chronic: encephalomalacia; Wallerian degeneration
acute: more dense than CSF
Acyanotic congenital heart disease comprises numerous etiologies, which can be divided into those with increased pulmonary vascularity (pulmonary plethora) and those with normal vascularity:
increased pulmonary vascularity
ventricular septal defect (VSD)
atrial septal defect (ASD)
Adamantinomas are rare primary malignant bone tumors that in the vast majority of cases occur in the tibia of young patients.
In the past, ameloblastomas, which are benign, locally aggressive bone tumors of the mandible, were also known as adamantinomas of the mandible. The two ent...
The Adams forward bend test is clinical test to assess the presence of a scoliosis.
Exclusion of a limb length discrepancy is considered important prior to performing the test. The patient is asked to bend forward with feet together, arms hanging and knees extended until the back bec...
The Adams-Oliver syndrome (AOS) is a rare disorder characterized by aplasia cutis congenita (missing hair and/or skin) and variable degrees of terminal transverse limb defects.
polymicrogyria: can be associated with a variant of Adams-Oliver syndrome 3
ADC pseudonormalization is a normal phase encountered in the subacute stage of ischemic stroke and represents an apparent return to normal healthy brain values on ADC maps which does not, however, represent true resolution of ischemic damage.
ADC pseudonormalization is seen typically around 1 w...
Adding images to an article is an important way of illustrating various imaging examples of that condition. Ideally, there should only be one image per case (usually the 'best' image) per article unless you wish to highlight a specific point, or it is a rare condition with only one case availabl...
Additive manufacturing is a process, such as stereolithography, in which objects are created by adding layer after layer from the ground up. This process can be contrasted with subtractive manufacturing, a process in which unneeded material is removed to create the desired object in the same way...
The adductor brevis muscle is a muscle in the medial compartment of the thigh that lies immediately deep to the pectineus and adductor longus.
origin: external surface of body of pubis and inferior pubic ramus
insertion: pectineal line and proximal part of linea aspera of femur
The adductor canal (also known as the Hunter canal or subsartorial canal) is a muscular tunnel in the thigh. It commences at the inferior end of the femoral triangle and terminates at the adductor hiatus.
from apex of the femoral triangle to the adductor hiatus
Adductor canal syndrome (also known as adductor canal compression syndrome) is a rare, non-atherosclerotic cause of arterial occlusion and limb ischemia 1. There is compression of the superficial femoral artery (SFA) in the adductor canal.
External compression of the superficial f...
The adductor hallucis muscle arises by two heads, an oblique and transverse head. It is responsible for adducting the big toe.
transverse head: ligaments associated with metatarsophalangeal joints of lateral three toes
oblique head: bases of metatarsals II to IV and from sheat...
The adductor longus muscle is a muscle in the medial compartment of the thigh that lies anterior to the adductor magnus muscle.
origin: external surface of body of pubis (triangular depression inferior to pubic crest and lateral to pubic symphysis)
insertion: linea aspera on middle o...
The adductor magnus muscle is the largest and deepest of the muscles in the medial compartment of the thigh. Like the adductor longus and brevis muscles, the adductor magnus is a triangular or fan-shaped muscle anchored by its apex to the pelvis and attached by its expanded base to the femur.
The adductor minimus muscle is a small, variably present muscle in the medial compartment of the thigh.
Due to confusion about this muscle over the years it has ended up with a variety of names, which include pars lateralis, adductor quartus muscle, premier faisceau du grand addu...
The adductor pollicis muscle is a large triangular muscle anterior to the plane of the interossei that crosses the palm of the hand. It is deep to the thenar eminence, forming part of the short muscles of the thumb, and the intrinsic muscles of the hand.
transverse head: 3rd m...
The adductor tubercle is a bony protuberance on the medial condyle of the femur and is located superior to the medial epicondyle. It demarcates the inferior most aspect of the medial supracondylar line. The adductor tubercle is the point of insertion for the adductor minimus and the hamstrings p...
Adenocarcinoma of the endometrium is the commonest histological subtype of endometrial cancer and accounts for up to 90% of such cases 1.
serous type adenocarcinoma of the endometrium
clear cell type adenocarcinoma of the endometrium
Adenocarcinoma in situ, minimally invasive adenocarcinoma and invasive adenocarcinoma of the lung are relatively new classification entities which replace the now-defunct term bronchoalveolar carcinoma (BAC).
In 2011 the International Association for the Study of Lung Cancer (IASLC) and several...
Adenocarcinomas in situ (AIS) of the lung refer to a relatively new entity for a pre-invasive lesion in the lung. This entity partly replaces the noninvasive end of the previous term bronchoalveolar carcinoma. Adenocarcinoma in situ is defined as a localized adenocarcinoma of <3 cm that exhibits...
Adenocarcinoma of the appendix, also referred to as nonmucinous adenocarcinoma of the appendix, is an uncommon type of appendiceal epithelial neoplasm. Different from the appendiceal mucinous neoplasms, these tumors share similar epidemiology and pathology with colorectal adenocarcinoma.
Adenocarcinoma of the cervix is a histological subtype of carcinoma of the cervix.
Cervical adenocarcinoma is less common than squamous cell carcinomas (SCC) of the cervix, accounting for ~12.5% of all cervical cancer. Their proportionate prevalence is thought to be increasing an...
Adenocarcinoma of the lacrimal glands is rare, with few cases reported in the literature since it was first described in 1996 1. Primary adenocarcinoma of the lacrimal gland is extremely rare; only 9 cases have been reported in the literature 1,2. It can be classified into high- and low-grade ma...
Adenocarcinoma of the lung is the most common histologic type of lung cancer. Grouped under the non-small cell carcinomas of the lung, it is a malignant tumor with glandular differentiation or mucin production expressing in different patterns and degrees of differentiation.
This article brings...
Primary adenocarcinoma of the small bowel is about 50 times less common than colonic carcinoma.
Almost 50% of small bowel adenocarcinomas are found in the duodenum, especially near the ampulla. In the remaining cases, the jejunum is more commonly involved than the ileum1.
Adenocarcinoma of the urinary bladder is rare and accounts for only ~1% of all bladder cancers (90% are transitional cell carcinomas).
Metaplasia of urinary bladder induced by chronic irritation or infection can lead to adenocarcinoma. Pathological types of adenocarcinoma of the urin...
Adenoidal hypertrophy or enlargement in adults is much less commonly seen than in children. It is usually due to chronic infection or inflammation. HIV always needs to be excluded as a cause.
In general, the adenoid tonsils enlarge after birth, maximizing by 6 years old. Thereafter, ...
Adenoidal hypertrophy or enlargement in children is common and due to an increase in the size of the adenoids. For adenoidal enlargement in adults, which is much rarer and usually pathological, please see the separate article, adenoidal hypertrophy (adults).
Adenoid cystic carcinomas are a rare histological subtype of adenocarcinoma.
Adenoid cystic carcinomas are generally considered low grade 4. The tumors have a notable tendency for perineural spread.
They have a wide distribution and mainly occur in relation to the airways,...
Adenoid cystic carcinoma (ACC) of the lacrimal glands is an extraconal malignancy usually originating from the orbital lobe of the lacrimal gland.
It often presents with orbital pain and paresthesia, since this type of tumor is frequently associated with perineural spread...
Adenoid cystic carcinoma (ACC) of the breast is a rare subtype of breast cancer.
They account for only 0.1-0.4% of all breast cancers.
The tumor demonstrates a strikingly characteristic microscopic pattern similar to that of adenoid cystic carcinoma of the salivary gla...
Adenoid cystic carcinoma (ACC) of the lung is a type of non-small cell lung cancer.
They are classified under lung carcinomas of the salivary gland type. Primary occurrence in the lung parenchyma is rare, while in the thorax they occur more commonly as adenoid cystic carcinoma of the...
Adenoid cystic carcinoma of the salivary glands is the second most common malignancy involving the minor salivary glands behind mucoepidermoid carcinoma and the second most common malignancy involving the parotid gland.
Adenoid cystic carcinomas arise more commonly in the minor saliv...
Adenoid cystic carcinomas of the tracheobronchial tree are a type of low-grade tracheal tumor. They are considered to be the second most common primary tumor of the trachea.
They are usually first recognized in patients in their 4th and 5th decades. There is no recognized gender p...
Adenoid facies, also known as the long face syndrome, refers to the long, open-mouthed face of children with adenoid hypertrophy.
The most common presenting symptoms are
chronic mouth breathing
The most dangerous feature is sleep apnea.
The characteristic faci...
The adenoid tonsils, or often just simply the adenoids (also known as the nasopharyngeal or pharyngeal tonsils), are paired foci of lymphatic tissue located on the superoposterior wall of the nasopharynx and form part of Waldeyer's ring.
Adenolipoma of the thyroid gland (also known as a thyrolipoma or a thyroid hamartoma) is a rare, benign fat-containing thyroid lesion. These lesions are usually well encapsulated and are composed of varying degrees of follicular thyroid tissue (thyroid adenoma) and mature adipose tissue; the amo...
The adenoma-carcinoma sequence refers to a stepwise pattern of mutational activation of oncogenes (e.g. K-ras) and inactivation of tumor suppressor genes (e.g. p53) that results in cancer. An oncogene is a gene that has the potential to cause cancer. In tumor cells, these are often mutated or ex...
Adenoma malignum of the cervix, also referred to as minimal deviation carcinoma / minimal deviation adenocarcinoma, is considered a rare variant of cervical mucinous adenocarcinoma.
It is thought to represent ~1-3% of all cervical adenocarcinomas. It can present in a wide age gro...
Adenomatoid odontogenic tumors are rare and differ from most other dentition related lesions in that they more frequently occur in the maxilla.
They are also seen more frequently in females, most frequently in the second decade of life.
They present as an e...
Adenomatoid tumors of the scrotum are benign, solid extratesticular lesions that can originate from the epididymis, tunica vaginalis, or spermatic cord (90% derived from the funiculus).
They are the most common extratesticular neoplasm, and most common tumor of the epididymis, and...
Adenomatous breast lesions are benign tumors which grow from glandular parenchyma. The breast is a conglomeration of various glandular tissues, hence they can be of several types.
apocrine adenoma of breast
pleomorphic adenoma of breast
Adenomatous endometrial hyperplasia is a type of endometrial hyperplasia.
The peak incidence is around 40-50 years of age.
Both endogenous and exogenous estrogen exposure are considered important factors in its etiology 1.
An adenomyoma is a focal region of adenomyosis resulting in a mass, which is difficult to distinguish from a uterine fibroid, although in general the degree to which the contour of the uterus is distorted is less marked in adenomyosis 2. Additionally, the 'mass' is poorly defined and blends with...
Adenomyomatosis of the gallbladder is a hyperplastic cholecystosis of the gallbladder wall. It is a relatively common and benign cause of diffuse or focal gallbladder wall thickening, most easily seen on ultrasound and MRI.
Adenomyomatosis is relatively common, found in ~9% of al...
Adenomyosis (or uterine adenomyosis) is a common uterine condition of ectopic endometrial tissue in the myometrium, sometimes considered a spectrum of endometriosis. Although most commonly asymptomatic, it may present with menorrhagia and dysmenorrhea. Pelvic imaging (i.e. ultrasound, MRI) may s...
An adenomyotic cyst is an extremely rare variation of cystic adenomyosis. The lesion consists of a large hemorrhagic cyst, which is partly or entirely surrounded by a solid wall. It can be entirely within the myometrium, submucosal, or subserosal and frequently is associated with symptoms of men...
Adenosine is a vasodilating agent, which acts on the vascular smooth muscle surface and leads to vasodilation and a considerable increased vascular flow.
Note: This article aims to give a rough description of adenosine.
For detailed and exact information please refer to the information and di...
Adenosis of the breast is a benign lobulocentric proliferative process in which lobules are enlarged and increased in number in addition to an increased number of glands within each lobule.
Pathologically subclassified into three main subtypes which include:
sclerosing adenosis of the breast
Adenosquamous cell carcinoma (ASC) of the cervix is a rare histological subtype of cervical carcinoma.
It has components of both cervical adenocarcinoma and cervical squamous cell carcinoma.
An adenosquamous histology appears to be an independent predictor of poor outcome...
Adenosquamous carcinoma of the endometrium is a rare histological subtype of endometrial cancer.
In general, it occurs in a slightly younger group when compared with pure adenocarcinoma of the endometrium 4.
It contains both malignant glandular and malignant squamous components. Adenosquamous...
Adenosquamous carcinoma of the lung is a rare type of non-small cell lung cancer containing both components of lung adenocarcinoma and lung squamous cell carcinoma (SCC).
It is thought to constituting 0.4-4% of cases non-small cell lung cancer.
cigarette smoking 8
Adhesive atelectasis refers to the specific form of lung atelectasis that occurs due to the decrease or absence of pulmonary surfactant produced by type II pneumocytes. Without sufficient surfactant the alveoli collapse due to increased surface tension. It is most commonly seen in neonates with ...
Adhesive capsulitis of the shoulder, also known as frozen shoulder, is a condition characterized by thickening and contraction of the shoulder joint capsule and surrounding synovium. Adhesive capsulitis can rarely affect other sites such as the ankle 8.
The incidence in the genera...
Adhesive otitis media is a form of chronic otitis media where there is an adhesion of medial ear structures as a result of chronic inflammation. There are often complete or partial adhesions between the thin retracted and atrophic pars tensa and the medial wall of the middle ear. Soft tissue deb...
Adie pupil (also known as tonic pupil) is caused by idiopathic degeneration of the ciliary ganglion, which sometimes occurs following a viral or bacterial illness. It is usually unilateral and typically affects young females 1.
Adie pupil represents a large dilated "tonic pupil", which does not...
Adie syndrome, also known as Holmes-Adie syndrome, is a rare neurological disorder.
Adie syndrome is a rare condition which is most commonly seen in young females in their fourth decade of life 2,3.
Patients most commonly present with a classic triad of:
The ADIR (ADduction and Internal Rotation) position relates to MR arthrography of the shoulder joint.
When added to a neutral-position shoulder protocol, MR arthrography in the ADIR position facilitates the diagnosis of labroligamentous lesions in patients with recurrent shoulder dislocations, ...
Adjacent level ossification is a complication of anterior cervical discectomy and fusion (ACDF) with anterior plate stabilization. It represents pathological heterotopic ossification of the soft tissues above or below the ends of the plate, contiguous with the adjacent vertebral body. It occurs ...
Adjacent segment degeneration is a common complication of spinal fusion occurring at the adjacent unfused level above or below the fused segment. It is usually encountered in the cervical spine or lumbar spine and occurs with an incidence of roughly between 2% and 4% per year 4.
Adnexa is a general term that refers to the accessory structures of an organ.
Adnexa have been described in relation to:
hair follicles, sweat glands, nails
structures in the mastoid (posterior) wall of the middle ear, e.g. mastoid antrum, aditus ad an...
Adrenal abscesses are rare lesions affecting the adrenal glands and are usually encountered in the setting of disseminated infection.
Although cases have been described in both neonates and adults, no systematic literature is available on the epidemiology of adrenal abscesses.
Adrenal adenomas, also known as adenomata, are the most common adrenal lesion and are often found incidentally during abdominal imaging for other reasons. In all cases, but especially in the setting of known current or previous malignancy, adrenal adenomas need to be distinguished from adrenal m...
The adrenal glands are highly vascular. Threefold arterial supply includes the:
superior adrenal arteries: typically 6-8 in number, arising from the ipsilateral inferior phrenic artery
middle adrenal artery: one or more, arising from lateral side of abdominal aorta
inferior adrenal artery: o...
Adrenal calcification is not a rare finding in healthy asymptomatic people and is usually the result of previous hemorrhage or tuberculosis. Addison disease patients only occasionally develop calcification.
sepsis: Waterhouse-Friderichsen syndrome
An adrenal collision tumor or collision tumor of the adrenal gland is an uncommon condition where two histologically distinct tumors abut each other or are in close proximity in the same adrenal gland.
Collision tumors have been reported in nearly every organ, for example, collision ...
Adrenal congestion is considered to possibly precede non-traumatic adrenal hemorrhage 1, and refers to adrenal gland thickening and peri-adrenal fat stranding on imaging, which are nonspecific findings. However, more research is needed to elucidate this entity.
A possible explanation for adrena...
Primary adrenal cortical carcinoma (also known as adrenocortical carcinoma) is a highly malignant but rare neoplasm. It may present as a hormonally active or an inactive tumor.
Although men and women are affected equally, functioning tumors are more common in females, who are als...
Adrenal cysts are rare lesions that are usually found incidentally on imaging performed for other reasons.
Adrenal cysts are reported to be rare with an incidence of <1% 1.
Patients can present with pain or swelling, although a significant portion (~40%) ...
The adrenal (suprarenal) glands (often shortened to just the adrenals) are paired organs of the endocrine system, often asymmetric in shape.
Each gland is enclosed in the perirenal fascia and each has a body and two limbs: a medial limb and a lateral limb. However, the right adr...
Adrenal glands protocol is an MRI protocol comprising a group of MRI sequences put together to further assess indeterminate adrenal lesions, in particular, lipid-poor adenomas.
Note: This article is intended to outline some general principles of protocol design. The specifics will vary depend...
Adrenal gland trauma most commonly results from blunt force trauma.
Adrenal gland trauma is present on 1-2% of CT imaging in blunt trauma although the occurrence is thought to be much higher as injury has been demonstrated at 28% in one autopsy series 1-4.
The right adrenal glan...
Despite its small size, the adrenal gland is affected by a relatively large number of neoplastic entities:
adrenal cortical carcinoma
adrenal lesions: for a more general list of...
Adrenal hemangiomas are rare benign tumors that are usually incidentally identified (one example of an adrenal incidentaloma). Its significance mainly relates to the difficulty in differentiation from other malignant lesions.
Although these can be found at any age, they are most ...
Adrenal hemorrhage can result from a variety of traumatic and non-traumatic causes. When unilateral, it is often clinically silent. In contrast, bilateral adrenal hemorrhage can lead to catastrophic adrenal insufficiency.
The large majority of patients with unilateral adr...
Adrenal hyperplasia refers to non-malignant growth (enlargement) of the adrenal glands and is a rare cause of ACTH-independent Cushing syndrome, with unilateral adrenal cortical adenomas being the commonest. Approximately 20% of Conn syndrome cases are secondary to adrenal hyperplasia. In diffus...
Adrenal insufficiency refers to inadequate secretion of corticosteroids (glucocorticoids and mineralocorticoids).
It may occur from partial or complete destruction of the adrenal cortex, in which case it is termed primary adrenal insufficiency (also known as Addison disease). Secon...
Adrenal lesions cover a broad spectrum from benign to neoplastic entities. Due to increased use of cross-sectional imaging they are frequently detected as incidental lesions (incidentalomas). If found incidentally, please refer to the Management of Incidental Adrenal Masses: American College of ...
An adrenal lipoma is an extremely rare macroscopic fat containing adrenal lesion. with only a handful of cases described in literature 1.
Like other lipomas elsehwre in the body, they are benign tumors of mesenchymal origin that contain mature fatty tissue and are surrounded by a fib...
Adrenal lymphangiomas, also known as cystic adrenal lymphangiomas, are rare, benign cystic adrenal lesions.
Adrenal lymphangiomas are extremely rare; prevalence is estimated at 0.06% 8. They can occur at any age, with a peak incidence between the 3rd and 6th decades of life. Accor...
Adrenal lymphoma can refer to:
primary adrenal lymphoma: rare
can be bilateral in around 70% of cases 1
secondary involvement of the adrenal glands with lymphoma: more common
The presentation can be variable and may include adrenal insufficiency, worsening general sta...
Adrenal metastases are the most common malignant lesions involving the adrenal gland. Metastases are usually bilateral but may also be unilateral. Unilateral involvement is more prevalent on the left side (ratio of 1.5:1).
They are present at autopsy in up to 27% of patients with ...
Adrenal myelolipomas are rare, benign and usually asymptomatic tumors of the adrenal gland characterized by the predominance of mature adipocytes.
On imaging, they usually present as large masses with a variable amount of fat-containing components.
Rare tumors with estimated aut...
Adrenal pseudocysts account for ~40% of adrenal cysts and are more likely than simple adrenal cysts to be symptomatic.
Pseudocysts do not have an epithelial lining and typically arise after an episode of adrenal hemorrhage. There is an ~7% association with malignancy (e.g. from hemor...
An adrenal teraoma is a very rare adrenal lesion. They account for around 0.7% of all primary adrenal tumors. As with teratomas in general, they are composed of mature tissues arising from more than one germinal layer.
They classically demonstrate a large fatty/lipomatous...
Tuberculous adrenalitis is the result of adrenal mycobacterium tuberculosis (TB) infection. Its incidence has decreased in the western world with the declining incidence of tuberculosis.
As the tuberculous infection causes destruction of the adrenal cortex, primary adrenal insufficie...