Abdominal Pain Patient Laboratory and Imaging

Laboratory and Imaging Studies
Pregnancy test: Positive Negative	Often the single most useful test in this setting. Modern urine or serum pregnancy tests are highly reliable. A positive pregnancy test helps focus your attention in the right direction, while a negative pregnancy test helps eliminate some of the more common abnormalities.
Quantitative HCG	If the pregnancy test is positive, it may be useful to know how much HCG is present. Generally, if the quantitative HCG is greater than 1500-2000 units, an intrauterine pregnancy will be consistently seen on transvaginal ultrasound. This is useful in ruling in or out ectopic pregnancies.
Transvaginal Ultrasound	This is very reliable in identifying ovarian cysts, fibroids, pregnancies, and free fluid in the pelvis. It can identify appendicitis, but is less reliable, with false negatives and occasional false positives.
CT Scan of the Abdomen	Most useful in identifying or ruling out such GI problems as appendicitis, diverticulitis, bowel obstruction, renal stone, and intra-abdominal abscesses.
CBC	Often ordered and infrequently helpful, the results are most helpful in the extreme: A very high WBC (>15,000) usually means the patient is pretty sick with something. A very low (<9 gm) hemoglobin usually means the patient has experienced significant but relatively slow bleeding. Rapidly bleeding patients usually go into shock before they are able to mobilize enough fluid to dilute their hemoglobin. A patient with a slowly-bleeding ectopic pregnancy may have a low blood count, if enough time passes. A patient without any previous bleeding from her ectopic who suddenly and catastrophically blows out the ectopic with torrential internal hemorrhage probably will have a near normal blood count when she arrives in the emergency room in hypovolemic shock, but with fluid resuscitation, the Hgb and Hct will dilute down significantly.
Gonorrhea/Chlamydia Cultures	Sometimes helpful in identifying those patients needing treatment for these sexually-transmitted infections. Even when positive, however, the presence of gonorrhea or chlamydia does not necessarily mean that they are responsible for the pelvic or abdominal pain.

Laboratory tests and imaging studies can be helpful in guiding you in the right direction on abdominal and pelvic pain. Not all tests are needed in all patients with abdominal pain. You will need to make a judgment, based on the clinical presentation, history and physical exam, and availability.