Chapter 36: ACUTE PELVIC PAIN: TRANSVAGINAL AND DOPPLER EVALUATION

INTRODUCTION

Patients with acute pelvic pain often pose a diagnostic dilemma. This stems from the similar signs and symptoms which many of these patients exhibit, the most common being nausea, vomiting, and leukocytosis. The differential considerations encompass multiple gynecologic causes such as hemorrhagic ovarian cysts, pelvic inflammatory disease, ectopic pregnancy, and ovarian torsion, as well as nongynecologic etiologies which include appendicitis, urinary calculi, inflammatory bowel disease, diverticulitis, and mesenteric adenitis. Transvaginal (TVS) and transabdominal (TAS) pelvic sonography have the ability to narrow the differential diagnosis and are the imaging modalities of choice when a gynecological etiology is suspected. Not only is it noninvasive, radiation-free, and cost-effective, sonography accurately delineates the architecture of the uterus and ovaries.¹ Computed tomography (CT) is used more frequently when a gastrointestinal or genitourinary abnormality is more likely.

The role of pelvic sonography in the evaluation of acute pelvic pain has been well described. Due to better anatomic resolution, TVS rather than TAS should be used whenever possible, although TAS is recommended when uterine and adnexal structures are beyond the field of view of the transvaginal probe, such as above the pelvic brim. The introduction of the vaginal probe into the vagina to determine whether pelvic structures move independently of each other (sliding organ sign) or are the source of the patient's pain are also helpful techniques. In addition, duplex and color or power Doppler imaging can be used to characterize vascularity to the ovaries, adnexal structures, and uterus, which may also be beneficial in narrowing the field of differential considerations.

A serum β human chorionic gonadotropin (hCG) level is usually performed when a female in the reproductive years presents with acute pelvic pain. Knowledge of pregnancy is of utmost importance for diagnostic reasons (determine whether the pain could be associated with pregnancy such as ectopic pregnancy) and safety reasons (whether the patient may have CT, which uses ionizing radiation). A negative hCG essentially excludes the diagnosis of a live intrauterine pregnancy and acute ectopic pregnancy because it becomes positive approximately 9 days after conception. Studies published in the late 1980s, which correlated the presence of a gestational sac using TVS with β-hCG levels, have played a crucial role in our ability to make this diagnosis. These studies documented the presence of a gestational sac by the time the hCG level was 1000 to 2000 mIU/mL (IRP [International Reference Preparation]).^{2,3, and 4} When the hCG level is above this discriminatory zone, one should expect to see a gestational sac, and if not an ectopic pregnancy is very likely. The high specificity of adnexal findings, which include the classic "tubal ring," has been widely reported in the literature. Further discussion of ectopic pregnancy may be found in Chapter 4.

The following is a review of sonographic characteristics of ...