Ultrasound Glossary

Mitral stenosis is a narrowing of the mitral valve that restricts blood flow from the left atrium to the left ventricle, evaluated by echocardiography.

A modality refers to a particular imaging technique or method, such as ultrasound, CT, or MRI.

A moiré artifact is a wavy or linear striping pattern that can appear on ultrasound when the transducer is held at certain angles.

A molar pregnancy is an abnormal pregnancy caused by a genetic error during fertilization, appearing on ultrasound as a characteristic heterogeneous mass with small cysts.

A monoamniotic pregnancy occurs when twins share both a placenta and an amniotic sac, the highest-risk type of multiple gestation.

A monochorionic pregnancy is one in which twins share a single placenta but may have separate or shared amniotic sacs.

Motion artifact occurs when patient movement or breathing disrupts the ultrasound image, making it blurry or distorted.

Mucinous adenocarcinoma is a type of cancer that produces mucin, often occurring in the gastrointestinal tract, detectable on ultrasound as a mass.

A multicystic dysplastic kidney is an abnormal kidney consisting of non-communicating cysts, typically non-functional and not requiring treatment.

A multinodular goiter is an enlarged thyroid gland containing multiple nodules, commonly evaluated with ultrasound.

Multiple gestations refer to pregnancies with more than one fetus, requiring careful ultrasound assessment to determine chorionicity and amnionicity.

Sonographic Murphy sign — focal tenderness directly over the gallbladder during ultrasound examination, indicating acute cholecystitis.

Muscle tissue, visible on ultrasound as hypoechoic linear bundles, is a fundamental structure of the musculoskeletal system.

Ultrasound imaging of tendons, muscles, ligaments, nerves, and joints for diagnosis of soft tissue injuries and guidance of injections.

Myasthenia gravis is an autoimmune neuromuscular disease that can be associated with thymic abnormalities visible on ultrasound.

A mycotic aneurysm is an infected aneurysm, typically resulting from bacterial seeding during bacteremia or endocarditis.

A myelencephalocele is a severe form of neural tube defect in which brain tissue herniates through an opening in the skull.

A myelomeningocele is a neural tube defect in which the spinal cord and meninges herniate through an opening in the vertebral column.

A myoma is a benign smooth muscle tumor, most commonly found in the uterus where it is called a fibroid or leiomyoma.

Myopia, or nearsightedness, causes high optical power in the eye, which can lead to unusual findings when eyes are scanned with ultrasound.

Myxedema is severe hypothyroidism characterized by accumulation of mucopolysaccharides in the skin and soft tissues.

A myxoma is a cardiac tumor, most commonly arising from the left atrium, visible on echocardiography.

The nasal bones are small bones in the nose that can be measured on prenatal ultrasound as a marker for chromosomal abnormalities.

The region immediately adjacent to the transducer face where the ultrasound beam is relatively uniform before spreading.

Neovascularization is the formation of new blood vessels, which can be detected on color Doppler ultrasound as a sign of inflammation or malignancy.

A nephroblastoma is a malignant kidney tumor in children, also known as Wilms tumor, visible as a renal mass on ultrasound.

Nephrolithiasis is the medical term for kidney stone disease, with stone appearance and location best shown on ultrasound.

Nephroptosis is abnormal mobility or descent of the kidney, potentially visible on ultrasound when the patient changes position.

Nephrotic syndrome is characterized by severe proteinuria and reduced serum proteins, with ultrasound used to evaluate kidney size and echogenicity.

Nerves are bundles of nerve fibers visible on high-resolution ultrasound, particularly during musculoskeletal and peripheral nerve examination.

Compression of a peripheral nerve within an anatomic tunnel, evaluated on ultrasound by increased nerve cross-sectional area.

Neural tube defects are congenital malformations of the brain or spinal cord resulting from failure of the neural tube to close during fetal development.

A neuroblastoma is a malignant tumor of neural crest origin, most commonly arising in the adrenal gland, visible as a renal or suprarenal mass on ultrasound.

Neurofibromatosis is a genetic disorder characterized by the development of neurofibromas (tumors of nerve tissue), visible as soft tissue masses on ultrasound.

A neuroma is a benign tumor of nerve tissue that can occur in various locations, including common sites like the interdigital space of the foot.

Newborn screening refers to the use of ultrasound in newborn infants to detect congenital abnormalities and disease.

Nodal metastasis refers to cancer spread to lymph nodes, visible on ultrasound as enlarged or abnormal-appearing lymph nodes.

A nodule is a small, discrete lesion or abnormality, typically less than 10 millimeters in diameter, visible on ultrasound.

Nonalcoholic fatty liver disease is the accumulation of excess fat in the liver in patients without significant alcohol consumption.

Nonechogenic is a term describing structures that do not produce ultrasound echoes, appearing completely dark on ultrasound images.

Nonimmune hydrops fetalis is severe fluid accumulation in the fetus not caused by Rh incompatibility, detectable on prenatal ultrasound.

Nuchal cord occurs when the umbilical cord wraps around the fetal neck, readily detected on prenatal ultrasound.

The nuchal fold is a measurement of skin thickening at the back of the fetal neck, used as a prenatal screening marker for chromosomal abnormalities.

A sonographic measurement of fluid at the back of the fetal neck at 11–14 weeks, used to screen for chromosomal abnormalities.

Nucleation is the process by which gallstones or kidney stones begin to form, with factors affecting nucleation studied in stone disease research.

Ultrasound imaging of the pregnant uterus to evaluate fetal development, anatomy, growth, and well-being.

A fluid-filled sac within the ovary containing an oocyte, visualized on ultrasound during ovulation monitoring.

Twisting of the ovary on its pedicle causing ischemia — a gynecologic emergency evaluated with Doppler ultrasound.

Enlargement of the main pancreatic duct on ultrasound, normally less than 3 mm — a key finding in pancreatitis and pancreatic ductal adenocarcinoma.

A standard echocardiographic view showing the left ventricle, mitral valve, aortic valve, and aortic root in a long-axis plane.