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Point-of-care pelvic ultrasound
Overview
This chapter illustrates the basic features of pelvic ultrasound by outlining the exploration of the female genital system, concluding thus the holistic approach (HOLA) ultrasound concept of the abdominal examination (see Chapters 1 and 44 ). Clinician-performed point-of-care pelvic ultrasound is an integral skill in a growing number of medical subspecialties. History and physical examination are not always reliable in the evaluation of possible pelvic pathology, especially in the critically ill patient. The ability to diagnose life-threatening conditions at the bedside can decrease time to diagnosis. Ultrasonography is the preferred imaging modality for female pelvic anatomy in both the nonpregnant and pregnant patient. The accuracy of clinician-performed bedside ultrasound in identifying pelvic pathology has been well established.
Indications
Abdominal pain, pelvic pain, and vaginal bleeding are common complaints for which pelvic ultrasound is used. Although less common, pelvic ultrasound may also be indicated for syncope, dizziness, abdominal or pelvic mass on physical examination, trauma, fever, and hemodynamic instability. In the setting of pregnancy, the first and foremost use of pelvic ultrasound is in the diagnosis of an intrauterine pregnancy (IUP). Once an IUP has been established, ultrasonography can be further used to document gestational age, fetal heart rate, subchorionic hemorrhage, abnormal pregnancies, pregnancy loss, or to follow normal pregnancy. For the nonpregnant, critically ill patient, other pertinent applications include the evaluation of life-threatening ovarian pathology, such as ovarian torsion, ovarian cyst rupture with associated hemorrhage, and tubo-ovarian abscess. In any female who is hypotensive, septic, febrile, or suffering from severe abdominal pain, pelvic ultrasound is an extremely useful tool to direct appropriate treatment. ,
Technique and normal anatomy
Imaging of the pelvic organs is assisted by the use of both transabdominal sonography (TAS) and transvaginal sonography (TVS). Each technique has its own advantages in the assessment of pelvic organs. A transabdominal approach gives the examiner spatial orientation of the pelvis and defines the relationship of the uterus with adjacent pelvic and abdominal structures. It is also helpful to delineate large masses, free fluid, and other pathology extending outside of the true pelvis. A transvaginal approach is useful because of probe proximity to the pelvic organs and the higher frequency resulting in images with superior resolution. This approach provides more anatomic detail of pelvic structures, allowing early identification of intrauterine contents and adnexal abnormalities. In addition, the probe can be used to detect the mobility of the pelvic organs. This can reveal adhesions and highlight pelvic pathology. These two modalities are complimentary, and in the undifferentiated patient, we recommend using both approaches.
Transabdominal technique
For TAS, scanning starts in the suprapubic area, using a low-frequency curvilinear transducer. The examination is best performed with a full bladder, although an overly distended bladder will decrease image quality. The bladder acts as an acoustic window and also displaces bowel loops from the pelvis for better imaging. With the indicator directed cephalad, sagittal images can be obtained by sweeping the transducer slowly from right to left. Transverse images can be obtained with the indicator to the patient’s right, by convention. By gently sweeping the transducer caudad and cephalad, all organs can be imaged in all three dimensions. The examiner should first start with an assessment of the uterus in both the sagittal and transverse planes. The position of the uterus, whether it is anteverted or retroverted, should be noted. Obesity and retroverted position can present challenges to the sonographer. The various portions of the uterus are then identified, namely, the cervix, body, fundus, and endometrial stripe. Sonographically, the normal uterus exhibits a low-gray homogenous texture. The endometrial stripe is typically seen as an echogenic line in the middle of the uterus ( Figures 43 E-1 and 43 E-2 ). The appearance of uterine endometrium changes as the thickness of the endometrium changes with different phases of menstrual cycle. The cervix has similar sonographic appearance to that of the rest of the uterus. The thin linear hyperechoic vaginal canal is visualized between the anechoic urinary bladder (anterior) and the echogenic rectum (posterior). The cul-de-sac should be evaluated for free fluid or hematoma or mass, both in long and transverse planes. Next, the operator moves the transducer to the right or left lower quadrants to identify the adnexa. The identification of the ovaries is aided by identifying the iliac vessels, which define the borders of the pelvis. The ovaries are often adjacent to them. Ovaries are identified by their “chocolate chip cookie” appearance of hypoechoic follicles within the ovary. Again, they should be imaged in two planes, sagittal and transverse. Ovarian size can be evaluated by measuring the ovary’s dimensions in three planes. Normal ovarian measurements are approximately 5.1 ± 3.1 cm in the preovulation period, 3.2 ± 1.7 cm in the postovulation period, and 1.3 ± 0.6 cm in postmenopausal women. Ovaries may not always be seen on TAS but are visualized 65% to 99% of the time when performed in the radiology suite. ,
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