Some very small transducers can be placed onto the end of a catheter and inserted into blood vessels to examine the walls of blood vessels. Ultrasound is commonly used for diagnosis, for treatment, and for guidance during procedures such as biopsies. It can be used to examine internal organs such as the liver and kidneys, the pancreas, the thyroid gland, the testes and the ovaries, and others.
An ultrasound scan can reveal whether a lump is a tumor. This could be cancerous, or a fluid-filled cyst. It can help diagnose problems with soft tissues, muscles, blood vessels, tendons, and joints. It is used to investigate a frozen shoulder , tennis elbow , carpal tunnel syndrome , and others.
Doppler ultrasound can assess the flow of blood in a vessel or blood pressure. It can determine the speed of the blood flow and any obstructions. An echocardiogram ECG is an example of Doppler ultrasound. It can be used to create images of the cardiovascular system and to measure blood flow and cardiac tissue movement at specific points. A Doppler ultrasound can assess the function and state of cardiac valve areas, any abnormalities in the heart, valvular regurgitation, or blood leaking from valves, and it can show how well the heart pumps out blood.
A carotid duplex is a form of carotid ultrasonography that may include a Doppler ultrasound. This would reveal how blood cells move through the carotid arteries. Ultrasound is often used by anesthetists to guide a needle with anesthetic solutions near nerves.
Most scans take between 20 and 60 minutes. It is not normally painful, and there is no noise. Michelle Oakley 2 Dr. Theresa Ollivett 2 E. Liz Cox 1 E. Medical Imaging distributor 1 E. Medical discount 1 E. Medical donation 1 E.
Medical facebook 1 E. Posts by Topic E. Recent Posts. About Us. This means you can go home the same day. Or it may be done as part of a longer stay in the hospital. The way the procedure is done may vary. In most cases, the procedure will follow this process:. If you are having a transabdominal ultrasound, you will be asked to raise your shirt to expose your abdomen. For a transvaginal ultrasound, you will be asked to remove your clothes from the waist down.
You will be given a sheet to place over your legs. You may be asked to remove jewelry or other objects. For a transabdominal procedure, a clear gel will be placed on the skin of your belly abdomen. The transducer will be moved over the area and pressed against the skin.
For a transvaginal ultrasound, you will need to lie on your back. Your feet will be in stirrups and your knees apart. A vaginal transducer probe will be covered with a sterile cover. In the case of the urethral atresia, as seen here in early pregnancy, the large fetal bladder bl , urinary ascites asc , and hydronephrotic kidneys K are all seen in the same transverse image.
Amniotic fluid is a physiologic extension of the fetus. Abnormalities of amniotic fluid volume are nonspecific findings that warrant further investigation. Polyhydramnios is defined as an amniotic fluid volume in excess of mL. The clinical diagnosis is made by the findings of a large-for-date uterine size, increased fluid, and a normal-size fetus. The excess fluid is seen as large anechoic areas on ultrasound.
In one-third of pregnancies complicated by polyhydramnios, no cause is determined. Oligohydramnios can be associated with fetal renal abnormalities, IUGR, postdate fetuses, or membrane rupture.
The clinical diagnosis is made when the fundal height is small and ultrasound examination shows little or no amniotic fluid. When amniotic fluid is decreased, the fetal small parts are crowded and the fetus is in contact with the uterine wall in most scanning planes. The amniotic fluid index, a sum of the largest vertical pocket of amniotic fluid in each of four quadrants of the uterus, is a useful semiquantitative measurement of fluid volume.
Severe oligohydramnios is present when the largest vertical pocket of amniotic fluid measures less than 1 cm. In the structurally normal fetus with intact membranes, severe oligohydramnios may be an indication for delivery. The biophysical profile is a test used in conjunction with antepartum fetal heart rate testing to evaluate fetal well-being in high-risk pregnancies.
It also incorporates the nonstress test as a measure of fetal reactivity. Each of these five parameters are assigned a score of 2 if normal and 0 if abnormal Table 3. The fetus is observed until all parameters are seen or until 30 minutes has elapsed. Table 3. Am J Obstet Gynecol , This observation period helps to distinguish the normal fetus with a physiologic periodic steep cycle from the chronically asphyxiated fetus with central nervous system depression.
A normal biophysical profile score of 8 to 10 is associated with a corrected perinatal mortality rate of 1 to 2 per Scores of 4 or less are highly predictive of intrauterine fetal jeopardy and, in a term fetus, are an indication for delivery. Low scores are associated with fetal distress in labor as well as low Apgar scores.
Vintzileos and colleagues 62 observed a good correlation between a low biophysical profile and fetal acidosis. In the extremely preterm fetus, a low score may not necessarily indicate the need for immediate delivery.
The clinician must weigh the risk of fetal distress or demise with the risks of prematurity. In this clinical situation, stabilizing any adverse maternal condition such as elevated blood glucose in a diabetic patient or high blood pressure in a hypertensive patient and repeating the biophysical test a short time later may be indicated.
There has been considerable interest in ultrasonographic evaluation of the cervix as a marker for assessing the risk of preterm birth Fig. It is clear that the length of the cervix decreases with advancing gestational age and that there is no cervical length at which the risk of preterm birth is zero. A cervical length of less than 25 mm indicates an increased risk of preterm birth, both in high-risk and in low-risk populations.
A single endovaginal cervical length measurement at 24 weeks can be used to assess risk status. If the maternal bladder is filled, the cervix Cvx can be seen clearly and measured. Cervical length of less than 25—30 mm is associated with an increased risk of preterm delivery. Ultrasound can be used to localize a favorable pocket of amniotic fluid before performing amniocentesis. A needle guide is available to aid the obstetrician with needle placement, but this can limit the operator's ability to move the needle in three dimensions.
It is preferable to insert the needle in a coplanar fashion i. Transplanar placement i. In chorionic villus sampling, the catheter is inserted into the placental bed under ultrasound guidance. Similarly, simultaneous real-time ultrasound guidance is used in percutaneous umbilical blood sampling or cordocentesis. Initially, 3D images were obtained by computer processing of multiple two-dimensional 2D images. Presently, real-time 3D images can be obtained Fig. The sonologist can obtain images which may not be readily available by conventional 2D sonography, and the images may not be as operator dependent as with 2D sonography.
A saggital view of the fetal brain to look at the corpus callosum, for example, not readily obtained on 2D study, can be obtained readily during volume manipulation of a 3D data set. It is clear that if image quality is poor in 2D, then it may also be suboptimal in 3D. Courtesy of GE Medical Systems.
There is an increasing body of research which indicates that 3D images may improve the accuracy of anomaly detection of the fetal face, ears, and distal extremities when compared to 2D images Fig. Obstetric ultrasound is an essential tool for the practicing clinician that can be used to improve obstetric care.
The ultrasound examination should include information about fetal number, presentation, biometry, placentation, fluid volume, and anatomy, and the images should be documented.
Routine or screening ultrasound may be useful to confirm dates, detect multiples earlier in pregnancy, assess placenta site, and obtain baseline biometry data.
For patients at increased risk, or those with an abnormal screening examination, referral to a tertiary center may be indicated. The information from diagnostic obstetric imaging can be used to assess fetal well-being in at-risk pregnancy and to facilitate invasive procedures such as amniocentesis.
J Ultrasound Med ; Ultrasound Q ; Am J Obstet Gynecol ; Obstet Gynecol ; AJR ; N Engl J Med ; Saari-Kemppainen A, Karjalainen O, Ylostalo P et al: Ultrasound screening and perinatal mortality: Controlled trial of systematic one-stage screening in pregnancy.
Lancet AIUM practice guideline for the performance of an antepartum obstetric ultrasound examination. JAMA ; Mantoni M: Ultrasound signs in threatened abortion and their prognostic significance. Practice Bulletin No. First-trimester or second-trimester screening, or both, for Down's syndrome.
N Engl J Med Cicero S, Curcio P, Papageorghiou A et al: Absence of nasal bone in fetuses with trisomy 21 at weeks of gestation: an observational study. Lancet ; Supulveda W, Wong AE, Dezerega V: First trimester ultrasonographic screening for trisomy 21 using fetal nuchal translucency and nasal bone.
Semin Perinatol ; Fetal biometry at weeks' gestation. Ultrasound Obstet Gynecol ; J Reprod Med ; Part 1: imaging. Placenta ; Obstet Gynecol Survey ; Seeds JW: Impaired fetal growth: Ultrasonic evaluation and clinical management.
Am J Perinatol ; Chavez, MR, Ananth CV, Smulian JC et al: Fetal transcerebellar diameter measurement with particular emphasis in the third trimester: a reliable predictor of gestational age.
Obstet Gynecol Heart ; Perinatal mortality by frequency and etiology Am J Obstet Gynecol ; Berghella V, Roman A, Daskalakis C et al: Gestational age at cervical length measurement and incidence of preterm birth. J Maternal Fetal Med ; Ultrasound-guided procedures for prenatal diagnosis and therapy. Obstet Gynecol Clin North Am ; Radiology ; Rad Clin North Am ; Chmail R, Pretorious D, Jones M et al: Prenatal evaluation of facial clefts with two-dimensional and adjunctive three-dimensional ultrasonography: A prospective study.
We use cookies to ensure you get the best experience from our website. By using the website or clicking OK we will assume you are happy to receive all cookies from us. Search Join Us. Navigation Top This chapter was last updated: March Diagnostic Obstetric Ultrasound Authors. William J. John W. Table 1.
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