An 18-year-old woman comes to your office because of abdominal pain. She states that the pain started yesterday afternoon and has been worsening. The pain is in the right lower quadrant and does not radiate. She rates it a 7 on a scale of 1 to 10. She has had some nausea but no vomiting. Nothing seems to improve or worsen the pain. She has a history of hypothyroidism for which she takes thyroid hormone replacement, and no other medical problems. She has never had surgery. She is allergic to penicillin. Physical examination is significant for right lower quadrant tenderness. Bimanual examination reveals right adnexal tenderness. Which of the following is the most appropriate next step in the diagnostic workup of this patient?
A. Abdominal computed tomography (CT)
B. Abdominal x-ray
C. Appendiceal ultrasound
D. Pelvic ultrasound
E. Urine human chorionic gonadotropin (hCG)
The correct answer is E. Ectopic pregnancy must be a primary consideration in the evaluation of any woman of childbearing age with abdominal pain or vaginal bleeding. Ectopic pregnancy is a leading cause of maternal morbidity and mortality and much of the problem stems from a delay in diagnosis and treatment. For any young woman who presents with abdominal pain or vaginal bleeding, an initial step in the workup therefore should be a pregnancy test. Current urine pregnancy tests are sensitive and suitable for use to determine if a patient is pregnant. If the patient is found not to be pregnant, then ectopic pregnancy can safely be removed from the differential diagnosis and further evaluation and treatment can proceed. If the patient is found to be pregnant a serum quantitative hCG level may be obtained to establish a level of the hormone and to guide further management. The patient should be questioned regarding sexual intercourse and date of the last menstrual period. A history of no recent sexual intercourse or a normal last menstrual period, however, does not obviate the need for a pregnancy test. Sexual histories are notoriously inaccurate as is the recall of the last menstrual period. Furthermore, patients can have bleeding from an ectopic pregnancy that they mistake for a menstrual cycle. The initial step in the evaluation of abdominal pain in this young woman thus should be a urine pregnancy test.
Abdominal computed tomography (CT) (choice A) is a helpful diagnostic tool for the evaluation of abdominal pain. It can identify appendicitis, diverticulitis, bowel obstruction, and numerous other intraabdominal conditions. In the pregnant patient with abdominal pain, however, pelvic ultrasound is the more appropriate initial radiologic study.
Abdominal x-ray (choice B) does not provide as comprehensive an evaluation of the abdomen and pelvis as does abdominal-pelvic CT or pelvic ultrasound. It would not be, therefore, the most appropriate next step.
Appendiceal ultrasound (choice C) can be used to evaluate a patient for appendicitis. The first step in diagnosing a young woman with abdominal pain, however, is to determine whether or not she is pregnant.
Pelvic ultrasound (choice D) is a useful tool for evaluating the uterus and adnexal structures in a young woman. Before performing the ultrasound it is helpful to know whether or not the patient is pregnant. In a nonpregnant female with significant abdominal pain, many physicians would opt for abdominal-pelvic CT as the initial radiologic study rather than pelvic ultrasound.