Ultrasound Studies
OVERVIEW OF ULTRASOUND STUDIES
Ultrasonography is a noninvasive procedure for visualizing soft tissue structures of the body by recording the reflection of inaudible sound waves directed into the tissues. The diagnostic procedure, which requires very little patient preparation, is now used in many branches of medicine for accurate diagnosis of certain pathologic conditions (Chart 13.1). It may be used diagnostically with
the obstetric, gynecologic, or cardiac patient and in patients with abnormal conditions of the kidney, pancreas, gallbladder, lymph nodes, liver, spleen, thyroid, or peripheral blood vessels. Frequently, it is used in conjunction with radiology or nuclear medicine scans. The procedure is relatively quick (often requiring only a few minutes to an hour) and causes little discomfort. No harmful effects have yet been established at the low intensities that are used (<100 mW/cm2). However, as with any diagnostic procedure, ultrasound should not be used frivolously. The terms ultrasound and sonogram are used interchangeably.
the obstetric, gynecologic, or cardiac patient and in patients with abnormal conditions of the kidney, pancreas, gallbladder, lymph nodes, liver, spleen, thyroid, or peripheral blood vessels. Frequently, it is used in conjunction with radiology or nuclear medicine scans. The procedure is relatively quick (often requiring only a few minutes to an hour) and causes little discomfort. No harmful effects have yet been established at the low intensities that are used (<100 mW/cm2). However, as with any diagnostic procedure, ultrasound should not be used frivolously. The terms ultrasound and sonogram are used interchangeably.
CHART 13.1 Uses of Ultrasound
Obstetric ultrasound: commonly performed to evaluate fetal health, size, and number of fetuses; level of amniotic fluid; and maternal and placental anatomy
Abdominal ultrasound: used to characterize soft tissue organs, including
Hepatobiliary: to evaluate organ size and presence of masses, calculi, or diffuse parenchymal conditions. Doppler ultrasound is helpful in demonstrating signs of portal hypertension. Pancreas: to detect pathologic states such as tumor involvement, pseudocysts, and inflammatory processes
Kidneys, ureters, and bladder: to diagnose cysts, masses, hydronephrosis, and certain diffuse conditions. Doppler evaluation of the renal vessels and parenchyma is commonly used to evaluate transplanted kidneys and in the staging of known renal cell carcinoma. Aorta and other large abdominal vessels: to detect aneurysms, the presence of clots or tumors, and other defects
Spleen and lymph nodes: to evaluate organ size and pathologic states such as lymphoma and metastatic spread of known cancers
Additional structures: to demonstrate suspected ascites, abscesses, retroperitoneal tumors, and signs of appendicitis
Pelvic ultrasound: Gynecologic scan is done to evaluate the urinary bladder, uterus, and ovaries; is used to monitor follicle development during infertility treatments and also as a guide for oocyte retrieval.
Male reproductive organs sonogram: used to evaluate scrotal masses and swelling and combined with Doppler examination of the penis to detect physiologic causes for male impotence. Transrectal ultrasound is an accepted method of screening for prostatic disease.
Head and neck sonogram: used to evaluate pathologies in the following structures:
Thyroid and parathyroid: for differentiating cysts from solid tumors
Carotid and vertebral arteries: to demonstrate vessel patency and flow patterns
Eye: to assist ophthalmologist in the removal of foreign bodies and in the evaluation of the eye’s structure
Neonatal brain: to diagnose cerebral hemorrhage and other intracranial pathologies.
Adult cerebral blood flow: By using a method known as transcranial Doppler, the larger blood vessels within the brain may be interrogated to rule out vascular disturbance.
Breast sonograms: performed to differentiate cysts from solid lesions and to guide cyst aspirations and needle biopsies
Extremities sonograms: used to evaluate arterial and venous blood flow and to characterize soft tissue masses such as Baker’s cysts. Sonography is often used to evaluate the pediatric hip for dislocations or other structural deformities. Certain adult joint anatomy can be visualized, such as the wrist in the evaluation of carpal tunnel syndrome.
Invasive procedures: serve as a guide for diagnostic procedures, such as paracentesis, amniocentesis, thoracentesis, and biopsy
Heart sonograms: performed to evaluate the cardiac structure and blood flow through chambers and valves
Principles and Techniques
Ultrasound uses high-frequency sound waves to produce an “echo map” that characterizes the position, size, form, and nature of soft tissue organs. Echoes of varying strength are produced by different types of tissues and are displayed as a visual pattern after computer processing of the echo information. The capability of acquiring real-time images means that ultrasound can readily demonstrate motion, as in the fetus or the heart. Ultrasound, however, cannot appropriately image air-filled structures such as the lungs.
Doppler Method
A phenomenon that accompanies movement, the Doppler effect, can be combined with diagnostic ultrasound imaging to produce duplex scans. Duplex scans provide anatomic visualization of blood vessels and a graphic representation of blood flow characteristics. Flow direction, velocity, and the presence of flow disturbances can readily be assessed. Certain equipment is capable of advanced Doppler imaging techniques, such as:
Color Doppler imaging provides a color-coded depiction of selected blood flow parameters.
A technology known as color Doppler energy, power Doppler, or color angio is sensitive to very low blood velocity states and is often used to evaluate blood flow through solid organs.
B-flow Doppler images the blood itself, producing images that resemble an angiogram.
These techniques establish the patency of a given blood vessel and are useful in investigating perfusion to an organ or mass. They are also helpful in evaluating complications in transplanted organs.
General Procedure
A gel or lubricant is applied to the skin over the area to be examined to conduct the sound waves.
An operator, known as a sonographer, holds a microphone-like device called a transducer. The transducer is moved over a specific body part, producing a display that is viewed on the monitor.
Sonography of structures in the abdominal region often requires that the patient control breathing patterns. Deep inspiration and exhalation may be used.
Selected images are recorded for documentation purposes.
The examination causes no physical pain. However, in certain applications, pressure may be applied to the transducer, causing some degree of discomfort. Long examinations may leave the patient feeling tired.
Tests usually take 20 to 45 minutes. This is the actual procedure time and does not include waiting and preparation times.
Some examinations require the patient to fast or to have a filled urinary bladder. Each examining department determines its own guidelines for patient preparation.
Advances in technology have allowed the development of very small, high-resolution transducers. Catheter-sized transducers are used to visualize blood vessels “from the inside out” during angiographic procedures. Endoscopic ultrasound is used to evaluate gastrointestinal lesions and may be used to visualize pancreatic biliary structures. Small transducers passed through the esophagus permit exquisite visualization of the heart during transesophageal echocardiography (TEE). Slim transducers are
introduced into the vagina to visualize gynecologic anatomy. Transrectal visualization of the prostate gland is an accepted method of screening for disease in the organ. Of course, before introduction into the body, these small transducers are properly cleansed and/or draped.
introduced into the vagina to visualize gynecologic anatomy. Transrectal visualization of the prostate gland is an accepted method of screening for disease in the organ. Of course, before introduction into the body, these small transducers are properly cleansed and/or draped.
Implications of Ultrasound Studies
Benefits and Risks
Ultrasonography is a noninvasive procedure with no radiation risk to patient or examiner.
It requires little, if any, patient preparation and aftercare.
As far as is known, the examination can be repeated as often as necessary without being injurious to the patient. No harmful cumulative effect has been seen.
Because ultrasound studies demonstrate structure rather than function, they may be useful for patients whose organ function is impaired.
Ultrasound is useful in the detection and examination of moving parts, such as the heart.
It does not require the injection of contrast materials or isotopes or ingestion of opaque materials.
Disadvantages
An extremely skilled examiner is required to operate the transducer. The scans should be read immediately and interpreted for adequacy. If the scans are not satisfactory, the examination must be repeated.
Air-filled structures (e.g., the lungs) cannot be studied by ultrasonography.
Certain patients (e.g., restless children, extremely obese patients) cannot be studied adequately unless they are specially prepared.
Difficult-to-Study Patients
The following general categories of patients may provide some difficulties in ultrasound studies:
Postoperative patients and those with abdominal scars: The area surrounding an incision is to be avoided whenever possible. If a scan must be performed over an incision, the dressing must be removed and a sterile coupling agent and probe must be employed.
Children and agitated adults: Because the procedure requires the patient to remain still, some patients may need to be sedated so that their movements do not cause artifacts.
Obese patients: Certain patients cannot be studied adequately in any case. For example, it may be difficult to obtain an accurate scan on a very obese patient, owing to alteration of the sound beam by fatty tissue. There is no preparation that would help here.
Interfering Factors
Barium has an adverse effect on the quality of abdominal studies, so sonograms should be scheduled before barium studies are done.
If the patient has a large amount of gas in the bowel, the examination may be rescheduled because air (bowel gas) is a very strong reflector of sound and does not permit accurate visualization.
OBSTETRIC AND GYNECOLOGIC SONOGRAMS
Obstetric SonogramUltrasound studies of the obstetric patient are valuable in (1) confirming pregnancy; (2) facilitating amniocentesis by locating a suitable pool of amniotic fluid; (3) determining fetal age; (4) confirming multiple pregnancy; (5) ascertaining whether fetal growth is normal, through sequential studies;
(6) determining fetal viability; (7) localizing placenta; (8) confirming masses associated with pregnancy; (9) identifying postmature pregnancy (increased amount of amniotic fluid and degree of placental calcification); (10) serving as a guidance method for chorionic villus sampling (CVS), embryo transfer, intrauterine device (IUD) extraction, and percutaneous umbilical vein sampling (PUVS); and (11) determining fetal nuchal translucency (FNT). A pregnancy can be dated with considerable accuracy if a sonogram is done at 20 weeks’ gestation and a follow-up scan is done at 32 weeks’ gestation. This validation is most important when early delivery is anticipated and prematurity is to be avoided. Conditions in which determination of pregnancy duration is useful include maternal diabetes, Rh immunization, and preterm labor (Chart 13.2).
(6) determining fetal viability; (7) localizing placenta; (8) confirming masses associated with pregnancy; (9) identifying postmature pregnancy (increased amount of amniotic fluid and degree of placental calcification); (10) serving as a guidance method for chorionic villus sampling (CVS), embryo transfer, intrauterine device (IUD) extraction, and percutaneous umbilical vein sampling (PUVS); and (11) determining fetal nuchal translucency (FNT). A pregnancy can be dated with considerable accuracy if a sonogram is done at 20 weeks’ gestation and a follow-up scan is done at 32 weeks’ gestation. This validation is most important when early delivery is anticipated and prematurity is to be avoided. Conditions in which determination of pregnancy duration is useful include maternal diabetes, Rh immunization, and preterm labor (Chart 13.2).
The pregnant uterus is ideal for echographic evaluation because the amniotic fluid-filled uterus provides strong transmitting interfaces between the fluid, placenta, and fetus. Ultrasonography has become the method of choice for evaluating the fetus and placenta, eliminating the need for the potentially injurious radiographic studies that were used previously.
Reference Values
Normal Obstetric Sonogram
Normal image of placental position, size, and structure
Normal fetal position and size with evidence of fetal movement, cardiac activity, and breathing activity
Adequate amniotic fluid volume
Normal fetal intracranial, thoracic, and abdominopelvic anatomy; four limbs visualized
Procedure
Most laboratories use a transvaginal (endovaginal) approach during the first trimester of pregnancy. No patient preparation is required for this method. Contact the laboratory performing the study to determine the method to be used.
Most laboratories use a transabdominal approach in the second trimester of pregnancy. Exceptions are made when the scan is performed to locate the placenta before amniocentesis, for evaluation of an incompetent cervix, or during labor and delivery. With this approach, the mother will need to have a full bladder. The patient is asked to drink five to six glasses of fluid (water or juice) about 1 to 2 hours before the examination. If she is unable to do so, intravenous fluids may be administered. She is asked to refrain from voiding until the examination is complete. Tell the patient that she will have a strong urge to void during the examination. Discomfort caused by pressure applied over a full bladder may be experienced. If the bladder is not sufficiently filled, three to four 8-oz glasses of water should be ingested, with rescanning done 30 to 45 minutes later. A full bladder allows the examiner to assess the true position of the placenta, repositions the uterus, and acts as a sonic window to the pelvic organs.
Have the pregnant woman lie on her back with her abdomen exposed during the test. This may cause some shortness of breath and supine hypotensive syndrome, which can be relieved by elevating the upper body or turning the patient onto her side.
In the transvaginal (endovaginal) procedure, a slim transducer, properly covered and lubricated, is gently introduced into the vagina. Because the sound waves do not need to traverse abdominal tissue, exquisite image detail is produced.
In the transabdominal approach, a coupling agent (special transmission gel, lotion, or mineral oil) is liberally applied to the skin to prevent air from absorbing sound waves. The sonographer slowly moves the transducer over the entire abdomen to obtain a picture of the uterine contents.
Check with your laboratory to determine the approach to be used.
Tell the patient that the examining time is about 30 to 60 minutes.
See Chapter 1 guidelines for intratest care.
CHART 13.2 Major Uses of Obstetric Ultrasound—Levels I and II*
Indications During First Trimester | |
Confirm pregnancy Confirm viability Rule out ectopic pregnancy in the first trimester Confirm gestational age.† | |
Birth control pill use Irregular menses No dates Postpartum pregnancy | |
Previous complicated pregnancy | |
Cesarean delivery Rh incompatibility Diabetes mellitus Fetal growth retardation | |
Clarify discrepancy between dates and size If large for dates, rule out: | |
Leiomyomas Bicornuate uterus Adnexal mass Multiple gestation Poor estimate of dates Missed abortion Blighted ovum | |
As guidance method for: | |
Chorionic villus sampling Amniocentesis Embryo transfer | |
Indications During Second Trimester | |
Establish or confirm dates.† | |
If no fetal heart tones: Clarify discrepancy between dates and size If large for dates, rule out: Poor estimate of dates Molar pregnancy Multiple gestation Leiomyomas Polyhydramnios Congenital anomalies | |
If small for dates, rule out: Poor estimate of dates Fetal growth retardation Congenital anomalies Oligohydramnios | |
If history of bleeding, rule out total placenta previa If Rh incompatibility, rule out fetal hydrops Evaluation and follow-up of suspected fetal anomalies | |
Indications During Third Trimester | |
If no fetal heart tones: Clarify discrepancy between dates and size | |
If large for dates, rule out: Macrosomia (diabetes mellitus) Multiple gestation Polyhydramnios Congenital anomalies Poor estimate of dates‡ | |
If small for dates, rule out: Fetal growth retardation Oligohydramnios Congenital anomalies Poor estimate of dates‡ | |
Determine fetal position, rule out: | |
Breech Transverse lie | |
If history of bleeding, rule out: | |
Placenta previa Abruptio placentae | |
Determine fetal maturity | |
Amniocentesis for lecithin/sphingomyelin ratio Placental maturity (grade 0-3) | |
Evaluation and follow-up of suspected fetal anomalies Estimation of fetal weight | |
Clinical Implications
During the first trimester, the following information can be obtained:
Number, size, and location of gestational sacs
Presence or absence of fetal cardiac activity and body movement
Presence or absence of uterine abnormalities (e.g., bicornuate uterus, fibroids) or adnexal masses (e.g., ovarian cyst, ectopic pregnancy)
Pregnancy dating (e.g., biparietal diameter, crown-rump length)
Presence and location of an IUD
During the second and third trimesters, ultrasound can be performed to obtain the following information:
Fetal viability, number, position, gestational age, growth pattern, and structural abnormalities
Amniotic fluid volume
Placental location, maturity, and abnormalities
Uterine fibroids and anomalies
Adnexal masses
Early diagnosis of fetal structural abnormalities makes the following choices possible:
Intrauterine surgery or other prenatal therapy
Discontinuation of pregnancy
Preparation of the family for care of a child with a disorder or planning of other options.
Fetal viability: Fetal heart activity can be demonstrated at 5 weeks’ gestation in most cases. This information is helpful in establishing dates and in the management of vaginal bleeding. Molar pregnancies (a nonviable fertilized egg implants into the uterus; the pregnancy will not come to term) and incomplete, complete, and missed abortions can be differentiated.
Gestational age: Indications for gestational age evaluation include uncertain dates for the last menstrual period, recent discontinuation of oral hormonal suppression of ovulation, bleeding episode during the first trimester, amenorrhea of at least 3 months’ duration, uterine size that does not agree with dates, previous cesarean birth, and other high-risk conditions.
Fetal growth: The conditions that serve as indicators for ultrasound assessment of fetal growth include poor maternal weight gain or pattern of weight gain, previous intrauterine growth retardation (IUGR), chronic infection, ingestion of drugs such as anticonvulsants or heroin, maternal diabetes, pregnancy-induced or other hypertension, multiple pregnancy, and other medical or surgical complications. Serial evaluation of biparietal diameter and limb length can help differentiate between wrong dates and IUGR. Doppler evaluation of the umbilical artery, uterine artery, and fetal aorta can also assist in the detection of IUGR. IUGR can be symmetric (the fetus is small in all measurements) or asymmetric (head and body growth vary). Symmetric IUGR may be caused by low genetic growth potential, intrauterine infection, maternal undernutrition, heavy smoking by the mother, or chromosomal aberration. Asymmetric IUGR may reflect placental insufficiency secondary to hypertension, cardiovascular disease, or renal disease. Depending on the probable cause, the therapy varies.
Fetal anatomy: Depending on the gestational age, the following structures may be identified: intracranial anatomy, neck, spine, heart, stomach, small bowel, liver, kidneys, bladder, and extremities. Structural defects may be identified before delivery. The following are examples of structural defects that may be diagnosed by ultrasound: hydrocephaly, anencephaly, and myelomeningocele are often associated with polyhydramnios (excessive accumulation of amniotic fluid; occurs in about 1% of pregnancies). Potter’s syndrome (renal agenesis) is associated with oligohydramnios defects (dwarfism, achondroplasia, osteogenesis imperfecta) and diaphragmatic hernias. Other structural anomalies that can be diagnosed by ultrasound are pleural effusion (after 20 weeks), intestinal atresias or obstruction (early pregnancy to second trimester), hydronephrosis, and bladder outlet obstruction (second trimester to term with fetal surgery available). Two-dimensional studies of the heart, together with echocardiography, allow diagnosis of congenital cardiac lesions and prenatal treatment of cardiac arrhythmias.
Detection of fetal death: Inability to visualize the fetal heart beating and separation of bones in the fetal head are signs of death. With real-time scanning, the absence of cardiac motion for 3 minutes is diagnostic of fetal demise.
Placental position and function: The site of implantation (e.g., anterior, posterior, fundal, in lower segment) can be described, as can location of the placenta on the other side of midline. The pattern of uterine and placental growth and the fullness of the bladder influence the apparent location of the placenta. For example, when ultrasound scanning is done in the second trimester, the placenta seems to be overlying the os (Latin for “mouth”) in 15% to 20% of all pregnancies. At term, however, the evidence of placenta previa (placenta is partially in lower uterine segment) is only 0.5%. Therefore, the diagnosis of placenta previa can seldom be confirmed until the third trimester. Placenta abruptio (premature separation of placenta) can also be identified. A transverse scan through the umbilical cord confirms the number of vessels. Doppler of the cord detects flow abnormalities.
Fetal well-being: Ultrasound findings are a major component of the biophysical profiles. The following physiologic measurements can be accomplished with ultrasound: heart rate and regularity, fetal breathing movements, urine production (after serial measurements of bladder volume), fetal limb and head movements, and analysis of vascular wave forms from fetal circulation. Fetal breathing movements are decreased with maternal smoking and alcohol use and increased with hyperglycemia. Fetal limb and head movements serve as an index of neurologic development. Identification of amniotic fluid measuring at least 1 cm is associated with normal fetus status. The presence of one pocket measuring <1 cm or the absence of a pocket is abnormal; it is associated with increased risk for perinatal death.
Assessment of multiple pregnancy: Two or more gestational sacs, each containing an embryo, may be seen after 6 weeks. Of twin pregnancies diagnosed in the first trimester, only about 30% will deliver twins, owing to loss or absorption of one fetus. Of value is assessment of the relative fetal growth of twins when IUGR or twin-to-twin transfusion is suspected. One cannot unequivocally diagnose whether twins are monozygotes (identical; develop from one zygote) or heterozygotes (fraternal; two eggs are fertilized) with ultrasound alone unless fetuses of opposite sex are evident. Routine ultrasound cannot totally be relied on to exclude the possibility of triplets or quadruplets, instead of only twins.
If the fetal position and amniotic fluid volumes are favorable, fetal sex can be determined by visualization of the genitalia. It must be cautioned, however, that sex determination is not the purpose of obstetric sonography.
Interfering Factors
Artifacts may be produced when the transducer is moved out of contact with the skin. This can be resolved by adding more coupling agent to the skin and repeating the scan.
Artifacts (reverberation) may be produced by echoes emanating from the same surface several times. This can be avoided by careful positioning of the transducer.
A posterior placental site may be difficult to identify because of the angulation of the reflecting surface or insufficient penetration of the sound beam owing to the patient’s size.
Interventions
Pretest Patient Care
A brief explanation of the procedure to be performed is given, emphasizing that it is not uncomfortable or painful and does not involve ionizing radiation that might be harmful to the mother or fetus. The studies can be repeated without harm, but the procedure is being studied carefully to determine whether there are any long-term adverse side effects. Benefits of the procedure should be explained.
Explain that a liberal coating of coupling agent must be applied to the skin so that there is no air between the skin and the transducer and to allow for easy movement of the transducer over the skin. A sensation of warmth or wetness may be felt. Although the acoustic couplant does not stain, advise the patient not to wear good clothing for the examination.
The woman may face the screen, and the sonographer may explain the images in basic terms. In some institutions, the father is encouraged to observe the testing. A photograph or videotape for the family to keep is sometimes provided.
See Chapter 1 guidelines for safe, effective informed pretest care.
CLINICAL ALERT
A full bladder may not be needed or desired for patients in the late stages of pregnancy or active labor. However, if a full bladder is required and the woman has not been instructed to report with a full bladder, at least another hour of waiting time may be needed before the examination can begin.
Endovaginal studies typically involve the use of a latex condom to sheath the transducer before it is inserted into the vaginal vault. Contact the laboratory if the patient has known or suspected latex sensitivity.
Fetal age determinations are most accurate during the crown-rump stage in the first trimester. The next most accurate time for age estimation is during the second trimester. Sonographic dating during the third trimester has a large margin of error (up to ±3 weeks).
Posttest Patient Care
Interpret test outcomes and counsel appropriately. Explain possible need for follow-up testing (e.g., fetal echocardiography) and/or treatment: medical (to stimulate early onset of labor) or surgical (fetal surgery or immediate surgery for ectopic pregnancy).
If fetal death is suspected, careful and considerate counseling and support are offered to parents.
Follow Chapter 1 guidelines for safe, effective, informed posttest care.
Fetal Echocardiography (Fetal Doppler)Fetal echocardiography is performed after the detection of a potential cardiac abnormality during an obstetric sonogram or in patients with a strong history of congenital cardiovascular disease. Additionally, women exposed to cardiac teratogens are usually advised to have this study. Not a screening procedure, fetal echocardiograms are most commonly performed in specialized laboratories or teaching hospitals. The heart is imaged in numerous planes, using pulsed Doppler and M-mode tracings (see Heart Sonogram), similar to an electrocardiogram. Valves and other cardiac structures are measured, and blood velocities and volumes are calculated. Optimal fetal echocardiographic studies are performed between 18 and 22 gestational weeks. Before 18 weeks, the fetal heart is too small, and after 22 weeks, image quality may be degraded by overlying structures.
Reference Values
Normal Sonogram
Normal structure of heart and great vessels
Normal heart rate and rhythm, with proper hemodynamic flow through heart and great valves
Procedure
Perform the fetal echocardiogram in the same manner as a routine obstetric scan, which also requires similar patient preparation, although a full bladder is not necessary. The pregnant patient lies on her back with the abdomen exposed. An acoustic coupling agent is applied to the skin, and a transducer is moved across the abdomen.
Although the fetal echocardiogram does not require the mother to have a full bladder, if combined with an obstetric sonogram, the mother is then required to have a full bladder. The patient is asked to drink
five to six glasses of fluid (water or juice) about 1 to 2 hours before the examination. If she is unable to do so, intravenous fluids may be administered. She is asked to refrain from voiding until the examination is complete. Tell the patient that she will have a strong urge to void during the examination. Discomfort caused by pressure applied over a full bladder may be experienced. If the bladder is not sufficiently filled, three to four 8-ounce glasses of water should be ingested, with rescanning done 30 to 45 minutes later.
See Chapter 1 guidelines for intratest care.
Clinical Implications
Abnormalities detected during fetal echocardiography include:
Cardiac arrhythmias
Septal defects, including tetralogy of Fallot
Hypoplastic heart syndrome
Valvular abnormalities, including Ebstein’s anomaly (abnormality of the tricuspid valve)
Cardiac tumors
Vessel abnormalities, including coarctation of aorta, transposition, aortic stenosis, truncus arteriosus, and pulmonary stenosis
Interfering Factors
Artifacts may be produced when the transducer is moved out of contact with the skin. This can be resolved by adding more coupling agent to the skin and repeating the scan.
Artifacts (reverberations) may be produced by echoes emanating from the same surface several times. This can be avoided by careful positioning of the transducer.
A posterior placental site may be difficult to identify because of the angulation of the reflecting surface or insufficient penetration of the sound beam owing to the patient’s size.
Interventions
Pretest Patient Care
A brief explanation of the procedure to be performed is given, emphasizing that it is not uncomfortable or painful and is not harmful to the mother or fetus. Explain that the procedure can be repeated without harm. Benefits of the procedure should also be explained.
Explain that a liberal coating of coupling agent must be applied to the skin so that there is no air between the skin and the transducer and to allow for easy movement of the transducer over the skin. A sensation of warmth or wetness may be felt. Although the acoustic couplant does not stain, advise the patient not to wear good clothing for the examination.
The woman may face the screen, and the sonographer may explain the images in basic terms. In some institutions, the father is encouraged to observe the testing. A photograph or videotape for the family to keep is sometimes provided.
See Chapter 1 guidelines for safe, effective informed pretest care.
Posttest Patient Care
Interpret test outcomes and counsel appropriately. Explain possible need for follow-up testing and/or treatment: medical (to stimulate early onset of labor) or surgical (fetal surgery or immediate surgery for ectopic pregnancy).
Follow Chapter 1 guidelines for safe, effective, informed posttest care.
Pelvic Gynecologic (GYN) Sonogram; Pelvic (Uterine Mass) Ultrasound Diagnosis; Intrauterine Device (IUD) LocalizationThe pelvic gynecologic ultrasound study examines the area from the umbilicus to the pubic bone in women. It may be used in the evaluation of pelvic masses to determine the position of an IUD, to evaluate postmenopausal bleeding, or to aid in the diagnosis of cysts, tumors, abscess, fibroids,
cancer, or thickened endometrium. Information can be provided on the size, location, and structure of masses. Spectral or color Doppler can be applied to pelvic vessels, demonstrating normal flow changes associated with the menstrual cycle, and can evaluate abnormal flow patterns to masses/tumors. The examination cannot provide a definitive diagnosis of pathology but can be used as an adjunct procedure when the diagnosis is not readily apparent. It is also used in treatment planning and follow-up radiation therapy for gynecologic cancer. Additionally, follicle development after infertility treatment can be monitored.
cancer, or thickened endometrium. Information can be provided on the size, location, and structure of masses. Spectral or color Doppler can be applied to pelvic vessels, demonstrating normal flow changes associated with the menstrual cycle, and can evaluate abnormal flow patterns to masses/tumors. The examination cannot provide a definitive diagnosis of pathology but can be used as an adjunct procedure when the diagnosis is not readily apparent. It is also used in treatment planning and follow-up radiation therapy for gynecologic cancer. Additionally, follicle development after infertility treatment can be monitored.
This test may be performed by a transvaginal method whereby a slim, covered, lubricated transducer is gently introduced into the vagina. A full bladder is not required. Because the sound waves do not need to transverse abdominal tissue, exquisite image detail is produced. This approach is most advantageous for examining the obese patient, the patient with a retroverted uterus, or the patient who has difficulty maintaining bladder distention. The transvaginal method is the approach of choice in monitoring follicular size during fertility workups and during aspiration of follicles for in vitro fertilization.
For pelvic sonograms using the transabdominal approach, a full bladder is necessary. The distended bladder serves four purposes: It acts as a “window” for transmission of the ultrasound beam; it pushes the uterus away from the pubic symphysis, thereby providing a less obstructed view; it pushes the bowel out of the pelvis; and it may be used as a reference for comparison in evaluating the internal characteristics of a mass under study.
Reference Values
Normal Sonogram
Normal pattern image of bladder, uterus, fallopian tubes, vagina, and surrounding structures
Normal Doppler flow patterns of major pelvic blood vessels
Procedure
Transabdominal Method
Have the patient lie on the back on the examining table during the test.
Apply a coupling agent to the area under study.
Place the active face of the transducer in contact with patient’s skin and sweep across the area being studied.
Tell the patient that the examination time is about 30 minutes.
Transvaginal (Endovaginal) Method
Have the patient lie on an examining table with hips slightly elevated in a modified lithotomy position. Drape the patient.
Lubricate and introduce a slim vaginal transducer, protected by a condom or sterile sheath, into the vagina. Some laboratories prefer that the patient insert the transducer herself. Depth <8 cm is all that is usually required.
Perform scans by using a slight rotation or movement of the handle and by varying the degree of transducer insertion. Typically, the transducer is inserted only a few inches into the vaginal vault.
Tell patient that the examination time is about 15 to 30 minutes.
See Chapter 1 guidelines for intratest care.
PROCEDURAL ALERT
If the patient is taking nothing by mouth (NPO) or in certain emergency situations, the patient may be catheterized and the bladder filled through the catheter if a transabdominal approach is required.
Endovaginal studies, when indicated, typically involve the use of a latex condom to sheath the transducer before it is inserted into the vaginal vault. Contact the laboratory if the patient has a known or suspected latex sensitivity.
Clinical Implications
Uterine abnormalities such as fibroids, intrauterine fluid collections, and variations in structure such as bicornuate uterus can be detected. Uterine and cervical carcinomas may be visualized, although definitive diagnosis of cancer cannot be made by sonography alone.
Endometrial abnormalities such as polyps can be visualized by sonography. This procedure involves distention of the endometrial canal with saline and subsequent ultrasound scanning. Very small adnexal masses may not be demonstrated by ultrasound studies. Masses identified on ultrasound may be evaluated in terms of size and consistency.
Cysts
Ovarian cysts (the most common ovarian mass detected by ultrasound) appear as smoothly outlined, well-defined masses. Cysts cannot be confirmed as either malignant or benign, but ultrasound studies can increase the suspicion that a particular mass is malignant.
A corpus luteum cyst is a single, simple cyst commonly visualized in early pregnancy.
Theca-lutein cysts are associated with hydatidiform mole, choriocarcinoma, or multiple pregnancy.
Because normal ovaries often have numerous visible small cysts, the diagnosis of polycystic ovaries is difficult to make on the basis of ultrasound alone.
Dermoid cysts or benign ovarian teratomas may be found in young adult women and have an extremely variable appearance. Because of their echogenicity, they are often missed on ultrasound. The only initial clue may be an indentation of the urinary bladder. When a dermoid cyst is suspected on ultrasound, a pelvic radiograph should be obtained.
Solid ovarian tumors such as fibromas, fibrosarcomas, Brenner’s tumors, dysgerminomas, and malignant teratomas are not differentiated by diagnostic ultrasound. Ultrasound documents the presence of a solid lesion but can go no further in narrowing the diagnosis.
Metastatic tumors of the ovary are common and may be solid or cystic in ultrasonic appearance. They are variable in size and are usually bilateral. Because ascites is often present, the pelvis and remainder of the abdomen should be scanned for fluid.
Pelvic inflammatory disease: Ultrasound differentiation between pelvic inflammatory disease and endometriosis is difficult. Evaluation of laboratory results and the clinical history leads to correct diagnosis. Other entities that may have similar ultrasonic presentation include appendicitis with rupture into the pelvis, chronic ectopic pregnancy, posttraumatic hemorrhage into the pelvis, and pelvic abscesses from various causes (e.g., Crohn’s disease [inflammatory bowel disease], diverticulitis).
Bladder distortion: Any distortion of the bladder raises the possibility of an adjacent mass. Tumor, infection, and hemorrhage are the major causes of increased thickness of the urinary bladder wall. Masses such as calculi and catheters may be seen within the bladder lumen. Urinary bladder calculi are highly echogenic. A urinary bladder diverticulum appears as a cystic mass adjacent to the urinary bladder. It may be mistaken for a cystic mass arising from some other pelvic structure, so attempts are made to demonstrate its communication to the bladder.
Ultrasound studies can help to determine whether a pelvic mass is mobile.
Solid pelvic masses such as fibroids and malignant tumors may be differentiated from cystic masses, which show sound patterns similar to those of the bladder.
Lesions may be shown to have metastasized.
Studies may aid in the planning of tumor radiation therapy.
The position of an IUD may be determined.
Interfering Factors
Results may be only fair, may vary with the patient’s habits and preparation (as described in Clinical Implications), and can be used only in conjunction with other studies. However, masses 1 cm and smaller can be seen with high-resolution equipment.
The success of a transabdominal scan depends on full bladder distention.
Interventions
Pretest Patient Care
Explain the purpose, benefits, and procedure of the test. Fasting is not required.
Have the patient drink four glasses of water or other liquid 1 hour before transabdominal scans. The patient should not void until the test is over.
Contact the laboratory performing the study to determine method to be used. If a transvaginal (endovaginal) approach is to be used, no patient preparation is required.
Explain that a liberal coating of coupling agent must be applied to the skin so that there is no air between the skin and the transducer and to allow for easy movement of the transducer over the skin. A sensation of warmth or wetness may be felt. Although the acoustic couplant does not stain, advise the patient not to wear good clothing for the examination.
Determine whether the patient has a latex sensitivity and communicate such sensitivities to the examining laboratory, if a transvaginal (endovaginal) approach is to be used. See latex precautions in Chapter 1.
Reassure the patient that she will have no pain or discomfort.
See Chapter 1 guidelines regarding safe, effective, informed pretest care.
Posttest Patient Care
Interpret test outcomes and counsel appropriately about possible further testing (biopsy with cytologic and histologic exam) and/or treatment (medical, pharmacologic, or surgical interventions).
Follow Chapter 1 guidelines for safe, effective, informed posttest care.
ABDOMINAL SONOGRAMS
Kidney (Renal) SonogramThe kidney sonogram is a noninvasive test used to visualize kidney parenchyma and associated structures, including renal blood vessels. This procedure is often performed after an intravenous pyelogram (IVP) to define and characterize mass lesions or the cause of a nonvisualized kidney. Because no contrast medium is administered, renal ultrasound is valuable for visualizing the kidneys of patients with iodine hypersensitivities. This procedure is also helpful in monitoring the status of a transplanted kidney, guiding stent and biopsy needle placement, and evaluating the progression of chronic conditions. Renal sonography is the preferred method for evaluating possible hydronephrosis in spinal cord injury patients.
Reference Values
Normal
Normal pattern image indicating normal size and position of kidneys, appropriate blood flow in renal vessels
Procedure
Have the patient lie quietly on an examining table. Scans are often performed with the patient in the decubitus position.
Apply warm oil or gel to the patient’s skin.
Ask the patient to inspire as deeply as possible for visualization of the upper parts of the kidney.
Tell the patient that the total study time varies from 15 to 30 minutes.
See Chapter 1 guidelines for intratest care.
PROCEDURAL ALERT
Scans cannot be done over open wounds or through dressings.
This examination must be performed before radiographic studies involving barium. If such scheduling is not possible, at least 24 hours must elapse between the barium procedure and the renal echogram.
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