OB Ultrasound ============= þ Definitions - IUP: gestational sack with thick concentric ring lying wihtin the endometrial echo of the uterus - LIUP (live IUP): above + cardioac activity - Abnormal IUP: gestational sac with thick concentric ring lying wihtin the endometrial echo of the uterus > 10 mm without a yolk sac, or definitive fetal pole and no cardiac activity - Extrauterine Gestation: Gestational sac > 5 mm with a thick concentric echogenic ring ling outside of the endometrial echo of theu terus with eithe ra yolk sac or fetal pole - NDIUP (no definitive IUP): Early IUP, abortion, ectopic: order formal US þ HCG levels - 1500, 5000 are the current discriminatory (endovaginal and abdominal) 2008 - If gestational sac mean sac diameter more than 8 mm and no yolk sac, may be abnormal. - If gestational greater than 16 mm and no fetal pole, probably will be abnormal. - Follicles are less than 3 cm. - Small amount of fluid in Pouch of Douglas is normal after ovulation. - A corpus luteum cyst is complex, not just black fluid. - Heterotopic without fertility drugs: 1:4000 (1:500 if IVF drugs; older literature said 1:30,000) þ Subchorionic hemorrage: small = < 1/3 of chorionic sac circumference: 7.7% AB risk moderate = 1/3-1/2 of sac: 9.2% AB risk large = > 2/3 of sac: 18.8% AB risk [Bennett GL. Subchorionic hemorrhage in first-trimester pregnancies: prediction of pregnancy outcome with sonography. Radiology 1996; 200:803-6.] þ sequence of expected events in early pregnancy ultrasound - See Also: - If quantative hCG exceeds discriminatory threshold (see below) and no sac seen on ultrasound, is highly specific for ectopic. - Study of 90 patients with abdominal pain and/or bleeding and HCG<1000, 13 had diagnostic ultrasound. Eight had IUP and four demonstrated an ectopic. [Dart R, et al. How useful are the history and physical in identifying ectopic pregnancy in patient with first-trimester pain and/or bleeding? (abstract presented at the meeting of SAEM, May 1996.)]. - remember if suspecting ectopic to check the blood type and consider giving Rhogam. - Endovaginal Ultrasound: ----------------------- by beta HCG of 1000-1500u [1300-1400 according to some](2000u to be safe): should see gestational sac via transvaginal US; which is about 4.5-5 weeks after last menstrual period. [Barnhart K, et al. Prompt diagnosis of ectopic preganancy in an emergency department setting. Obstet Gynecol 1994;84:1010-1015.] [Brennan EF. Ectopic pregnancy--Part II: diagnostic procedures and imaging. Acad Emerg Med 1995;2:1090-1097.] [Jehle D, et al. Ectopic pregnancy. Emerg Med Clin North Am 1994;12:55-71.] - Transabdominal Ultrasound: -------------------------- by transabdominal approach, should see gestational sac at bHCG of 6500 - Pseudosacs: ---------- beware of "pseudosacs": formed by decidual cast breakdown with an internal blood clot, tend to be centrally vs. eccentrically located, and seen in up to 20% of ectopics. [Brennan EF. Ectopic pregnancy--Part II: diagnostic procedures and imaging. Acad Emerg Med 1995;2:1090-1097.] - Staging: -------- + by 3-4 mm of decidual reaction should see gestational sac (with magnification) (check adnexa for an ectopic using the 7.5 MHz frequency if possible); should have two layers of endometrial decidua: "double decidual sac" sign. [Brennan EF. Ectopic pregnancy--Part II: diagnostic procedures and imaging. Acad Emerg Med 1995;2:1090-1097.] + by the time the gestational sac is up to 8 mm, you should see a yolk sac within the gestational sac; if not, it is abnormal (either a decidual reaction or a blighted ovum) + by the time the gestational sac is 16 mm, you should be able to see the embryo þ Ultrasound of fetal heartbeat - use M-mode through heart to document - may see heartbeat as early as 1 mm embryo size - heartbeat may start and stop so check for 5 full minutes - heartbeat is definitive proof of intrauterine pregnancy þ Heterotopic pregnancy (IUP + ectopic) - extremely rare - 1:4000 pregnancies [Jehle D, et al. Ectopic pregnancy. Emerg Med Clin North Am 1994;12:55-71.]