Pelvic Ultrasound Health Article

Definition

Pelvic ultrasound is a procedure in which high-frequency sound waves are used to create images of the pelvic organs by projecting the sound waves into the pelvis and measuring how the sound waves reflect, or echo, back from the different tissues.

Purpose

Ultrasound is a preferred method of examining the pelvis and functions as an extension of a physical examination, particularly for obese patients. It is a common initial step after physical examination when a patient complains of pelvic pain or abnormal vaginal bleeding. The procedure is performed routinely during pregnancy and examinations to determine the cause of infertility. Ultrasound has the ability to detect the size and shape of pelvic organs, such as the bladder, and is useful in evaluating the cause of bladder dysfunction. In women, pelvic ultrasound is used to examine the uterus, ovaries, and vagina. In general, ultrasound can detect inflammation, free fluid, cysts (abnormal fluid-filled spaces), and tumors in the pelvic region.

A primary use of pelvic ultrasound is during pregnancy. In early pregnancy (at about five to seven weeks), ultrasound may determine the size of the uterus or the fetus to confirm the suspected due date, to detect multiple fetuses, or to confirm that the fetus is alive (or viable). Ultrasound is particularly useful in distinguishing between intrauterine (within the uterus) and ectopic (outside the uterus) pregnancies. Toward the middle of the pregnancy (at about 16–20 weeks), the procedure can confirm fetal growth, reveal defects in the anatomy of the fetus, and check the placenta. Toward the end of pregnancy, it may be used to evaluate fetal size, position, growth, or to check the placenta.

Doctors may use ultrasound to guide the biopsy needle during amniocentesis and chorionic villus sampling. The imaging allows precise placement of the long needle that is inserted into the patient's abdomen to collect cells from the placenta or amniotic fluid.

Precautions

There are no special precautions recommended before an ultrasound examination. Unlike x rays, ultrasound does not produce harmful radiation so it does not pose a risk to the technologist, patient, or a fetus.

Description

Depending on the goal of the procedure, a pelvic ultrasound can also be called a bladder ultrasound, pelvic gynecologic sonogram, or obstetric sonogram. Ultrasound examinations are often done in a doctor's office, clinic, or hospital setting. Typically, the patient will lie on an examination table with the pelvis exposed. Special gel is applied to the area to make sure that there is no air between the hand-held transducer and the skin and to facilitate moving the transducer. The doctor or technologist will move the transducer over the abdomen. The transducer both creates and receives the echos of the high-frequency sound waves (usually in the range of 3.5-10.0 megahertz). An ultrasound scan reveals the shape and densities of organs and tissues. By performing repeated scans over time, much like the frames of a movie, ultrasound can also reveal movement, like the movement of a fetus. This technique is called real-time ultrasound.

Using a computerized tool, called a caliper, the ultrasound technologist can measure various structures shown in the image. For example, the length of the upper thigh bone (femur) or the distance between the two sides of the skull can indicate the age of the fetus.

Ultrasound technology has been used safely in medical settings for over 30 years, and several significant extensions to the procedure has made it even more useful. A specially designed transducer probe can be placed in the vagina to provide better ultrasound images. This transvaginal or endovaginal scan is particularly useful in early pregnancy or in cases where ectopic pregnancy is suspected. In men, transrectal scans, where the probe is placed in the rectum, are done to check the prostate. Doppler ultrasound has the ability to follow the flow of blood through veins and arteries and can be useful in detecting abnormalities such as abnormal blood flow associated with ovarian torsion, a twisted blood supply that causes pelvic pain. Color enhancement is particularly useful in Doppler imaging, where shades of red signify flow away from the transducer and shades of blue signify flow toward.

Hysterosonography is another variant ultrasound procedure. It involves the injection of saline solution into the uterus during an endovaginal scan. The saline distends the uterine cavity and simplifies the identification of polyps, fibroids, and tumors. The saline outlines the lesion, making it easier to find and evaluate. Hysterosonography can also be used in the testing of patency (openness) of the fallopian tubes during infertility evaluations.