Pelvic Ultrasonography

In pelvic ultrasonography, high frequency sound waves are reflected to a transducer to provide images of the interior pelvic area on a monitor. Techniques of sound imaging include A-mode (amplitude modulation, recorded as spikes), B-mode (bright­ness modulation), gray scale (a representation of organ texture in shades of gray), and real-time imaging (instantaneous images of the tissues in motion, similar to fluoroscopic examination). Selected views may be photographed for later examination and a permanent record of the test.

Purpose

• To evaluate symptoms that suggest pelvic disease and to confirm tentative diagnosis
• To detect foreign bodies and distinguish between cystic and solid masses (tumors)
• To measure organ size
• To evaluate fetal viability, position, gestational age, and growth rate
• To detect multiple pregnancy
• To confirm fetal abnormalities and maternal abnormalities
• To guide amniocentesis by determining placental location and fetal position

Patient preparation

• Describe the test to the patient, and tell her the reason it's being performed.
• Assure her that this procedure is safe, noninvasive, and painless.
• Because this test requires a full bladder as a landmark to define pelvic organs, instruct the patient to drink liquids and not to void before the test.
• Tell her who will perform the procedure and where and that it can vary in length from a few minutes to several hours.
• Explain that a water enema may be necessary to produce a better outline of the large intestine.
• Explain that sometimes a transvaginal sonogram may be performed to enhance visualization of pelvic structures.
• Reassure the patient that the test won't harm the fetus, and provide emotional support throughout.

Procedure and posttest care

• With the patient in a supine position, the pelvic area is coated with mineral oil or water-soluble conductive gel to increase sound wave conduction.
• The transducer is guided over the area, images are observed on the monitor, and good images are photographed.
• Remove the conductive gel from the patient's skin.
• Allow the patient to immediately empty her bladder after the test.

Normal findings

The uterus is normal in size and shape. The ovaries' size, shape, and sonographic density are normal. No other masses are visible. If the patient is pregnant, the gestational sac and fetus are of normal size in relation to gestational age.

Abnormal findings

Both cystic and solid masses have homogeneous densities, but solid masses (such as fibroids) appear more dense. Inappropriate fetal size may indicate miscalculated conception or delivery date, fetal anomalies, or a dead fetus. Abnormal echo patterns may indicate foreign bodies (such as an intrauterine device), multiple pregnancy, maternal abnormalities (such as placenta previa or abruptio placentae), fetal abnormalities (such as molar pregnancy or abnormalities of the arms and legs, spine, heart, head, kidneys, and abdomen), fetal malpresentation (such as breech or shoulder presentation), and cephalopelvic disproportion.

Interfering factors

• Failure to fill the bladder, obesity, or fetal head deep in the pelvis (possible poor imaging)