Articles

Articles are a collaborative effort to provide a single canonical page on all topics relevant to the practice of radiology. As such, articles are written and edited by countless contributing members over a period of time. A global group of dedicated editors oversee accuracy, consulting with expert advisers, and constantly reviewing additions.

1,233 results found
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Ligamentum teres (disambiguation)

The term ligamentum teres can refer to the: ligamentum teres of the abdomen (round ligament) ligamentum teres of the hip
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Ligamentum venosum

The ligamentum venosum is a fibrous remnant which travels superiorly from the porta hepatis of the liver to the inferior vena cava. It is often obliterated in adults.  In the fetus, it is patent and known as the ductus venosus which shunts blood returning from the placenta in the umbilical vein...
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Light bulb sign (pheochromocytoma)

The light bulb sign of an adrenal pheochromocytoma is an MRI feature of this tumor. It refers to marked hyperintensity on T2 weighted sequences, however, this finding is neither sensitive nor specific and pheochromocytomas are more often heterogeneous with intermediate or high T2 signal intensit...
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Lingual artery

The lingual artery is one of the branches of the external carotid artery and supplies the oral floor and tongue. Summary origin: branch of the external carotid artery at the level of the C3 course: towards hyoid bone, then loops down towards the tongue supply: oral floor and tongue terminat...
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Lipohyalinosis

Lipohyalinosis (also known as fibrinoid necrosis) is a disease affecting the small cerebral arteries associated with lacunar infarction and deep white matter changes related to small vessel chronic ischemia. Pathology The histopathological landmarks of lipohyalinosis are irregular fibrosis and...
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Lipomatous hypertrophy of the interatrial septum

Lipomatous hypertrophy of the interatrial septum (LHIS) is a relatively uncommon disorder of the heart characterized by benign fatty infiltration of the interatrial septum. It is commonly found in elderly and obese patients as an asymptomatic incidentally discovered finding.  Epidemiology The ...
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Liquefactive necrosis

Liquefactive necrosis is a form of necrosis where there is transformation of the tissue into a liquid viscous mass. Pathology In liquefactive necrosis, the affected cell is completely digested by hydrolytic enzymes leading to a soft, circumscribed lesion which can consist of fluid with remains...
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Loeys-Dietz syndrome

Loeys-Dietz syndrome is an autosomal dominant connective tissue disorder which has many features similar to Marfan syndrome. The disease is characterized by skeletal manifestations and vasculopathies. Although Loeys-Dietz syndrome shares many similarities with Marfan syndrome, the course is oft...
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Lower gastrointestinal bleeding

Lower gastrointestinal bleeding (LGIB) is defined as that occurring distal to the ligament of Treitz (i.e. from the jejunum, ileum, colon, rectum or anus) and presenting as either hematochezia (bright red blood/clots or burgundy stools) or melena. Epidemiology The incidence of lower gastrointe...
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Lower gastrointestinal bleeding (differential)

Lower gastrointestinal bleeding usually occurs distal to the ligament of Treitz, and has a wide differential diagnosis: diverticular disease enterocolitis infective Crohn’s disease ulcerative colitis ischemic colitis vascular malformation vascular ectasia angiodysplasia arteriovenous m...
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Lower limb anatomy

Lower limb anatomy encompasses the anatomy of all structures of the lower limb, including the hip, thigh, knee, leg, ankle, and foot. This anatomy section promotes the use of the Terminologia Anatomica, the international standard of anatomical nomenclature. 
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Luetic aneurysm

Luetic aneurysms (also called syphilitic aneurysms) are a type of aneurysm occurring usually secondary to syphilitic aortitis.  For a general discussion, and for links to other system-specific manifestations, please refer to the article on syphilis.  Pathology The responsible organism is a sp...
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Lumbar arteries

The lumbar arteries are paired branches of the abdominal aorta arising in the lumbar region. Gross anatomy Origin There are most commonly four paired lumbar arteries originating as posterolateral branches of the abdominal aorta on either side, at the level of L1-4. Course The paired arterie...
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LUMBAR syndrome

LUMBAR, PELVIS, or SACRAL syndrome is the association of infantile hemangiomas in the lower body with other extracutaneous congenital abnormalities in the region. The syndrome may be incomplete.   Pathology LUMBAR 1 lower body hemangiomas urogenital anomalies and ulceration myelopathy bony...
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Lumbar trunk

The lumbar trunks (TA: truncus lumbalis) are paired lymphatic trunks that join to form the cisterna chyli, forming an integral part of the lymphatic system. The lumbar trunks carry lymph from the infraumbilical abdominal wall, pelvis and lower limbs 1,2. The intestinal trunk in the majority of p...
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Lymph

Lymph (also known as lymphatic fluid) is the name given to the interstitial fluid once it has passed into the lymphatic vessels. Formation As blood passes through capillary beds a significant proportion of the plasma is filtered into the extracellular space. Most of this filtered tissue fluid ...
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Lymphangiosarcoma

Lymphangiosarcomas are rare malignant soft tissue neoplasms represent a vascular tumor (angiosarcoma) that occurs in patients with chronic lymphedema. Epidemiology It affects females more than males, as it is commonly associated with post-mastectomy lymphedema.  Clinical presentation Chronic...
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Lymphatic malformations

Lymphatic malformations are benign lesions of vascular origin that show lymphatic differentiation. Specifically, they are vascular malformations and not vascular tumors as per the 2018 ISSVA classification of vascular anomalies 5.  This article focuses on the general features of lymphatic malfo...
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Lymphatic system

The lymphatic system (also known as the lymphoid system or systema lymphoideum in Terminologia Anatomica) is the collective term given to the lymphatic vessels and lymphoid tissues in the body 1,4. Terminology Occasionally the lymphatic system is considered with the reticuloendothelial system ...
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Lymphocele

Lymphoceles are collections of lymphatic fluid that happen most frequently in the postoperative setting. Although they can occur in potentially any part of the body where lymphatic tissue is resected (e.g. lymphadenectomy) or injured in trauma, they are most commonly seen in the retroperitoneum....
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Lymphocele of the thoracic duct

Lymphoceles of the thoracic duct, also known as thoracic duct cysts, are lymph-filled collections/dilatations that can arise from any portion of the thoracic duct. The clinical significance of a thoracic duct cyst lies in its misidentification as a pathological lesion at radiological assessment...
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Lymphedema

Lymphedema is the pathologic accumulation of fluid in the soft tissues as the result of impaired lymphatic drainage, with resultant inflammation, adipose tissue hypertrophy, and fibrosis. It can be either primary or secondary, due to surgery or disease processes. The condition can cause disfigur...
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Lyre sign (carotid artery)

The lyre sign refers to the splaying of the internal and external carotid by a carotid body tumor. Classically described on angiography it is also visible on CT angiography.
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Macaroni sign (arteries)

The macaroni sign is a sign seen in Takayasu arteritis on ultrasound. It represents the smooth, homogeneous and moderately echogenic circumferential thickening of the arterial wall that occurs in Takayasu arteritis. The sign is highly specific for Takayasu arteritis, more commonly noted in the ...
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Major aortopulmonary collateral arteries

Major aortopulmonary collateral arteries (MAPCAs) are persistent tortuous fetal arteries that arise from the descending aorta and supply blood to pulmonary arteries in the lungs usually at the posterior aspect of hilum. Pathology Embryologically, the intersegmental arteries regress with the no...
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Malignant vascular tumors

Malignant vascular tumors are rare, accounting for <1% of all sarcomas.  Pathology intermediate grade hemangioendothelioma Kaposi sarcoma high grade hemangiopericytoma angiosarcoma
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Marfan syndrome

Marfan syndrome is a multisystem connective tissue disease caused by a defect in the protein fibrillin 1, encoded by the FBN1 gene. Cardiovascular involvement with aortic root dilatation and dissection is the most feared complication of the disease. Epidemiology The estimated prevalence is aro...
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Marginal artery of Drummond

The marginal artery of Drummond, also known as the marginal artery of the colon, is a continuous arterial circle or arcade along the inner border of the colon formed by the anastomoses of the terminal branches of the superior mesenteric artery (SMA) and inferior mesenteric artery (IMA). Gross a...
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Marginal artery of Drummond and arc of Riolan (mnemonic)

Remembering the colon vascular supply can be confusing because of inconstant collateral vascularization, therefore mnemonics can be helpful. One way to remember the location of the marginal artery of Drummond is to remember that it runs distally to the root of the mesentery (near the colon). I...
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Marginal sinus (foramen magnum)

The marginal sinus is a dural venous sinus and runs along the inner margin of foramen magnum. It has numerous communications with regional venous structures 1-2:  anteriorly: basilar venous plexus posteriorly: occipital sinus laterally sigmoid sinus veins of the hypoglossal canal inferiorl...
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Marsupial cava

Marsupial cava, also known as preaortic iliac venous confluence, is a rare anatomical variant in which the confluence of the common iliac veins is located anterior to the right common iliac artery and aortic bifurcation. Terminology The term marsupial cava is in reference to the normal anatomy...
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Masseteric artery

The masseteric artery is a small branch from the second part of the maxillary artery. It passes laterally through the mandibular notch to the deep surface of the masseter muscle. It supplies the muscle, and anastomoses with the masseteric branches of the external maxillary and with the transvers...
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Maxillary artery

The (internal) maxillary artery is the larger of the two terminal branches of the external carotid artery.  Origin and course The maxillary artery's origin is behind the neck of the mandible, at first, it is embedded in the substance of the parotid gland. From there it passes anterior between ...
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Maximum intensity projection

Maximum Intensity Projection (MIP) consists of projecting the voxel with the highest attenuation value on every view throughout the volume onto a 2D image 1. Such an algorithm is rather simple: for each XY coordinate, only the pixel with the highest Hounsfield number along the Z-axis is represe...
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May-Thurner syndrome

May-Thurner syndrome refers to a chronic compression of the left common iliac vein (CIV) against the lumbar vertebrae by the overlying right common iliac artery (CIA), with or without deep venous thrombosis 2. Although both left and right CIVs lie deep to the right common iliac artery, the left...
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McConnell’s capsular arteries

McConnell’s capsular arteries (MCCA) are one of the three major branches of the cavernous segment of the internal carotid artery (ICA). Gross anatomy They arise from the medial wall of the cavernous ICA distal to both the meningohypophyseal trunk and the inferolateral trunk. The McConnell’s c...
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Medial circumflex femoral artery

The medial circumflex femoral artery is usually a branch of the profunda femoris that arises close to its origin, usually before the origin of the lateral circumflex femoral artery. It provides blood to the femoral neck and damage to the artery or involvement of it in pathological processes may ...
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Medial frontobasal artery

The medial frontobasal artery is a branch of the A2 segment of the anterior cerebral artery (ACA) which runs forward and basally along the medial surface of the hemisphere towards the frontal pole, suppling the orbital part of the frontal lobe from its medial side.
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Medial lenticulostriate arteries

The medial lenticulostriate arteries are generally considered to arise from the A1 segment of anterior cerebral artery (ACA), and supply the globus pallidus and medial portion of the putamen 1,3.  They are shorter, thinner and fewer in number than the lateral lenticulostriate arteries, which ar...
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Medial posterior choroidal artery

The medial posterior choroidal artery is a small branch (often multiple - 40% of hemispheres) usually arising from the P2 segment of the PCA. It may also arise from one of the PCA branches, e.g. parieto-occiptal, calcarine, splenial artery. It ascends deep to the rest of the PCA and supplies sm...
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Medial umbilical folds

The medial umbilical folds are bilateral raised ridges of parietal peritoneum in the deep aspect of the anterior abdominal wall formed by the underlying medial umbilical ligaments running from the pelvis to the umbilicus. The medial umbilical ligaments are anatomical remnants of the obliterated ...
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Median antebrachial vein

The median antebrachial vein is a superficial vein of the anterior forearm that drains the superficial structures of the forearm and wrist between the basilic and cephalic veins. It ascends to the cubital fossa where it usually drains into the median cephalic and median basilic veins (collective...
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Median cubital vein

The median cubital vein is the superficial vein overlying the bicipital aponeurosis in the roof of the cubital fossa, commonly cannulated for intravenous access. It variably forms as either a H or M type pattern joining the median antebrachial, basilic and cephalic veins. If a M-shaped pattern, ...
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Median prosencephalic vein

The median prosencephalic vein (of Markowski) is a precursor to the vein of Galen; typically before birth, its anterior portion regresses with formation of the internal cerebral veins and its posterior portion persists as the vein of Galen. If an arterio-venous fistula exists, it balloons out to...
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Median sacral artery

The median sacral artery is a small single posterior branch of the distal abdominal aorta that descends to supply structures in the pelvis. Summary location: abdomen and pelvis origin and termination: originates as a posterior branch of the distal abdominal aorta just above the level of the b...
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Mediastinal hemangioma

Mediastinal hemangioma is a location specific subtype of a hemangioma. Epidemiology There incidence account for less than 0.5% among all mediastinal masses 1. Clinical presentation Up to half of patients may be asymptomatic 1. Others may present with non-specific symptoms, such as cough, che...
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Mediastinum (ITMIG classification)

The International Thymic Malignancy Interest Group (ITMIG) classification of mediastinal compartments was developed to reflect a division of the mediastinum based on cross-sectional imaging. It was in part an effort to consolidate prior discrepant classification systems in use by different medic...
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Medical devices in the head and neck

Medical devices in the head and neck are regularly observed by radiologists on plain film, CT and MRI reporting. They include devices which pass through the neck into the chest and stomach or ascend to/into the head. Vascular access devices dialysis catheters peripherally inserted central cat...
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Medical devices in the thorax

Medical devices in the thorax are regularly observed by radiologists when reviewing radiographs and CTs. Extrathoracic devices tubing, clamps, syringes, scissors, lying on or under the patient rubber sheets, foam mattresses, clothing, hair braids, nipple piercings, etc. may also be visible T...
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Meningohypophyseal trunk

The meningohypophyseal trunk, also known as the posterior trunk, is a branch of the C4 (cavernous) segment of the internal carotid artery. In contrast to the inferolateral trunk, it is almost always identified at autopsy. However, due to its small size, the meningohypophyseal trunk is seen only ...
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Meningo-ophthalmic artery

The meningo-ophthalmic artery is a variant arterial anatomy in which the entire supply to the ophthalmic artery derives from the middle meningeal artery. This variation represents one extreme of a spectrum of the persistence of the embryologic stapedial artery. Gross anatomy The meningo-ophtha...
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Mental artery

The mental artery is a terminal branch of the inferior alveolar artery which itself is a branch of the first part of the maxillary artery. It emerges onto the face from the mandibular canal with the mental nerve at the mental foramen, and supplies muscles and skin in the chin region. The mental ...
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Mercedes-Benz sign (aorta)

The Mercedes-Benz sign can be seen in the aorta in the context of aortic dissection on CT 1.  It is seen at three distinct intimal flaps that have a triradiate configuration similar to the Mercedes-Benz logo (Figure 1). Two of the three lumens outlined by these intimal flaps belong to the false...
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Mesenteric ischemia

Mesenteric ischemia, also commonly referred to as bowel or intestinal ischemia, refers to vascular compromise of the bowel and its mesentery that in the acute setting has a very high mortality if not treated expediently. Mesenteric ischemia is far more commonly acute than chronic in etiology. Th...
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Metabolic syndrome

The metabolic syndrome, also known as syndrome X, is a set of five conditions, which together increase a patient's risk of developing cardiovascular disease 1. Clinical presentation There are five central components of metabolic syndrome: hyperinsulinemia impaired glucose tolerance dyslipid...
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Mickey Mouse appearance

In medical imaging literature, a Mickey Mouse appearance has been given to imaging features that depict that of Mickey Mouse when viewed from the front. It has been described in the following: anencephaly 2 progressive supranuclear palsy 1 synonymously with a finger in glove sign the flared ...
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Mickey Mouse sign (ultrasound)

The Mickey Mouse sign is said to represent the normal anatomy of the common femoral artery, common femoral vein and great saphenous vein on ultrasound at the level just inferior the inguinal crease.  See also Mickey Mouse appearance
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Microscopic polyangiitis

Microscopic polyangiitis (MPA) is small vessel non-granulomatous necrotizing vasculitis. It most often affects venules, capillaries, arterioles, and small arteries, although it occasionally involves medium-sized arteries. Epidemiology It typically affects middle-aged individuals. Clinical pre...
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Microvascular decompression

Microvascular decompression is a surgical procedure for cranial nerve compression syndrome, most often carried out for trigeminal neuralgia, or less frequently hemifacial spasm and glossopharyngeal neuralgia. It is usually carried out via a retrosigmoid craniotomy. The culprit blood vessel, eit...
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Midaortic syndrome

Midaortic syndrome is an uncommon entity affecting children and young adults. It is characterized by progressive narrowing of the abdominal aorta and its major branches. Clinical presentation The onset of symptoms is usually during childhood or young adulthood 2: hypertension (most common) i...
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Middle adrenal artery

The middle adrenal (suprarenal) artery is one of the three adrenal arteries that supply the adrenal gland. Gross Anatomy Origin The middle suprarenal arteries arise from the aorta on each side between the inferior phrenic artery and the renal artery. They run laterally across the diaphragmati...
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Middle cardiac vein

The middle cardiac vein or posterior interventricular vein is a vein of the heart which accompanies the posterior interventricular artery. It courses in the posterior interventricular groove and drains directly into the coronary sinus close to it’s termination. It drains the posterior wall of bo...
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Middle cerebral artery

The middle cerebral artery (MCA) is one of the three major paired arteries that supply blood to the brain. The MCA arises from the internal carotid artery as the larger of the two main terminal branches (the other being the anterior cerebral artery), coursing laterally into the lateral sulcus wh...
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Middle cerebral artery (MCA) infarct

The middle cerebral artery territory is the most commonly affected territory in a cerebral infarction, due to the size of the territory and the direct flow from the internal carotid artery into the middle cerebral artery, providing the easiest path for thromboembolism. Clinical presentation Th...
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Middle colic artery

The middle colic artery is a branch of the superior mesenteric artery (SMA) and supplies the marginal artery. Course The middle colic artery passes in the layers of the transverse mesocolon to the transverse colon and divides into right and left branches right branch supplies the right portio...
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Middle collateral artery

The middle collateral artery is one of the two terminal branches of the deep brachial artery. As it descends in the distal part of the posterior compartment of the arm, it contributes to the arterial anastomosis of the elbow specifically the interosseous recurrent artery which is the proximal co...
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Middle hepatic artery

The middle hepatic artery (MHA) is an intrahepatic hilar arterial branch, usually arising from the left hepatic artery, which supplies segments 4a and 4b. It runs towards the right side of the umbilical fissure. Variant anatomy it may arise from the right hepatic artery 1,2 it may arise as a ...
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Middle meningeal artery

The middle meningeal artery is the dominant supply of the cranial dura. It arises from the first part of the maxillary artery, a terminal branch of the external carotid artery. It enters the middle cranial fossa via the foramen spinosum. Here it gives off two basal branches—the petrosal branch a...
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Middle rectal artery

The middle rectal artery, also known as the middle hemorrhoidal artery, is a branch from the anterior division of the internal iliac artery supplying the rectum. Summary origin: anterior division of the internal iliac artery location: pelvis supply: inferior rectum, seminal vesicles, prostat...
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Middle thyroid vein

The middle thyroid vein is a tributary of the internal jugular vein. Gross anatomy Origin and course The middle thyroid vein arises from the lateral surface of the thyroid. It traverses laterally to the internal jugular vein, passing anterior to the common carotid artery and posterior to the ...
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Minimal aortic injury

Minimal aortic injury (MAI) is a mild form of blunt traumatic aortic injury which are limited to the aortic intima and are recognized more frequently due to the use of high-resolution vascular imaging in trauma. Epidemiology Minimal aortic injuries account for 10-28% of all blunt traumatic aor...
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Mixed vascular malformation

A mixed vascular malformation is a relatively common congenital cerebral vascular malformation, most frequently composed of a developmental venous anomaly and a cavernous malformation. As developmental venous anomalies seldom bleed, the risk of a mixed vascular malformation is determined by the ...
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Modified Allen test

The modified Allen test (MAT) may be used to clinically assess the patency and completeness of the superficial palmar arch 1,2. Its classic use is in assessing for sufficient collateral flow to the hand, to avoid ischemia in the setting of radial artery puncture, cannulation, catheterization or ...
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Mönckeberg medial calcific sclerosis

Mönckeberg medial calcific sclerosis is characterized by calcific deposits within the media of medium and small muscular arteries that do not cause luminal narrowing. The calcification is typically diffuse and circumferential along the vessel and is readily visible on plain film. Vascular calcif...
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Moyamoya disease

Moyamoya disease is an idiopathic, non-inflammatory, non-atherosclerotic progressive vasculo-occlusive disease involving the terminal supraclinoid internal carotid arteries and circle of Willis.   Terminology The term moyamoya disease should be reserved for an idiopathic, sometimes familial, c...
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Moyamoya syndrome

Moyamoya syndrome, also termed the moyamoya pattern or phenomenon, is due to numerous conditions that can cause arterial occlusion of the circle of Willis, with resultant collaterals, and appearances reminiscent of moyamoya disease. These conditions include 1-4 : vessel wall abnormalities athe...
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Multiphase CT angiography in acute ischemic stroke

Multiphase CT angiography is an evolving imaging technique in acute ischemic stroke. The technique aims to quickly and reliably identify brain which is potentially salvageable with intervention. Brain tissue viability depends on many factors, with this technique assessing collateral leptomeninge...
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Musculophrenic artery

The musculophrenic artery is one of two terminal branches of the internal thoracic artery. Gross anatomy The musculophrenic artery runs along the costal slips of the diaphragm. It supplies the 7th, 8th and 9th intercostal spaces with paired anterior intercostal arteries, as well as fine branch...
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Musculoskeletal arteriovenous malformations

Musculoskeletal arteriovenous malformations (AVM) are typically congenital, growing with age and may not manifest until adolescence or adulthood. Spinal AVMs are discussed separately.  Clinical presentation Patients can present with a palpable mass (with or without erythema or a thrill) and/or...
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Musculoskeletal hemangiopericytoma

Musculoskeletal hemangiopericytomas are now considered to be a cellular and more aggressive version of solitary fibrous tumors, and the term has largely been abandoned.  Epidemiology These tumors are most frequently seen in middle-aged adults (~ 4th decade). Pathology The name is derived fro...
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Mycotic aneurysm

Mycotic aneurysms are aneurysms arising from infection of the arterial wall, usually bacterial. It is a complication of the hematogenous spread of bacterial infection, classically from the heart.  Epidemiology Mycotic aneurysms are thought to represent only a minority of (0.7-2.6%) of all aort...
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Myocardial bridging of the coronary arteries

Myocardial bridging is a common congenital anomaly of the coronary arteries where a coronary artery courses through the myocardium.  Epidemiology It is found approximately in 20-30% of the adult population in autopsy studies. The incidence in coronary angiograms is between 2-15% and can be eas...
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Necrotizing sarcoid granulomatosis

Necrotizing sarcoid granulomatosis (NSG) is a rare systemic disease, characterized by sarcoid-like granuloma formation, vasculitis and variable degrees of necrosis. It is sometimes classified under the group of pulmonary angiitis and granulomatosis. Terminology This remains a controversial ent...
Article

Needle gauge system

The needle gauge system, often called just the Gauge or G, is an internationally-used scale for sizing needles. It was adopted from pre-existing gauges which were used in industry to size metal wire. In contradistinction to the French scale, the other well-known sizing system, which is a metric...
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Neoplastic intracranial aneurysm

Neoplastic intracranial or cerebral aneurysms, also known as oncotic aneurysms, are a rare type of intracranial aneurysm attributed to metastatic tumor emboli. Epidemiology The entity is rare, with fewer than 100 cases being reported in the English literature at the time of a 2015 systematic r...
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Neurosyphilis

Neurosyphilis results from infection of the central nervous system by the spirochete Treponema pallidum, subspecies pallidum. The disease has a heterogeneous spectrum of early and late manifestations. For a general discussion, and for links to other system-specific manifestations, please refer ...
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Neurovascular compression syndromes

Neurovascular compression syndromes are a form of vascular compression disorders where there is usually compression or distortion of a cranial nerve due to a redundant or aberrant vascular structure. Clinical presentation Not all cases of neurovascular contact are clinically symptomatic. Prese...
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Non-AIDS associated Kaposi sarcoma

Non-AIDS associated Kaposi's sarcoma is a localized process which rarely involves lymph nodes or organs. For a discussion of Kaposi sarcoma in general, please refer to Kaposi sarcoma.  Epidemiology Sporadic (non-AIDS associated) Kaposi sarcoma is mostly seen in elderly males from the Mediterr...
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Non-occlusive mesenteric ischemia

Non-occlusive mesenteric ischemia is the second most common cause of acute mesenteric ischemia, with a higher incidence in hospitalized and critical care patients.  Epidemiology Non-occlusive mesenteric ischemia accounts for ~25% (range 20-30%) of acute mesenteric ischemia. It most commonly af...
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Norwood procedure

The Norwood procedure is a palliative procedure that is the first of three stages in the surgical treatment of hypoplastic left heart syndrome. The procedure consists of three components: constructing a neo-aorta by side-to-side anastomosis of the main pulmonary artery and ascending aorta, suc...
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Nutcracker phenomenon

The nutcracker phenomenon, also known as nutcracker anatomy or left renal vein entrapment, refers to the anatomic or pathophysiologic entity wherein the superior mesenteric artery compresses and impedes outflow of the left renal vein into the inferior vena cava. It can be a common incidental fin...
Article

Nutcracker syndrome

Nutcracker syndrome is a vascular compression disorder that refers to the compression of the left renal vein most commonly between the superior mesenteric artery (SMA) and aorta, although other variations can exist 1. This can lead to renal venous hypertension, resulting in rupture of thin-walle...
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Nyquist limit

The Nyquist limit represents the maximum Doppler shift frequency that can be correctly measured without resulting in aliasing in color or pulsed wave ultrasound.  Physics The Nyquist limit always equals Pulse Repetition Frequency (PRF)/2. The US machine can display the Nyquist limit either as ...

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