Ectopic Pregnancy on Ultrasound
Ectopic pregnancy is a pregnancy that occurs outside the uterine cavity. This most commonly occurs in the Fallopian tubes. Other less common places include the cervix, ovary and abdomen. Patient presentation is variable but can be mild such as pelvic pain and spotting. The most feared complication is when the pregnancy in the tube ruptures and causes bleeding which can be life threatening.
Many women who come to the emergency room early in pregnancy for pain or spotting will get an ultrasound. Often this is done to exclude an ectopic pregnancy since this can be life threatening. This can also date the pregnancy to see how far along it is. Other conditions can be diagnosed such as bleeding, cysts, fibroids, and twisted ovaries.
Doctors will order a blood test called a beta HCG. This is a hormone present in the blood when a women is pregnant. When the levels are greater than 1000-2000, we can expect to see an early pregnancy on ultrasound. The lack of a pregnancy on ultrasound in the uterus above 2000 for beta HCG becomes suspicious for ectopic pregnancy. Beta HCG is also used to follow a pregnancy as it increases rapidly normally and falls when a pregnancy fails.
Most commonly, we will see an ectopic pregnancy as a mass or complex cyst next to the ovary in the tube. This will often have what we call a ring of fire or blood flow around it. The uterus will not contain a pregnancy in most cases. A live pregnancy outside the uterus is certain for an ectopic pregnancy but seen in a minority of cases. A simple cyst uncommonly represents an ectopic pregnancy.
Sometimes we may not see a pregnancy in the uterus and we don’t see an ectopic pregnancy either. Suspicion should be high despite this if the beta HCG is above 2000. Free fluid in the pelvis also raises suspicion for an ectopic even if we don’t see one. Close follow up is needed in these cases.
A mass or complex cyst in the ovary is commonly seen during pregnancy and represents a corpus luteum in most cases. A corpus luteum is a structure involved in ovulation and early pregnancy. After the follicle ruptures and the egg is released into the fallopian tube, the corpus luteum is what is left. The corpus luteum secretes hormones to help with the early pregnancy. It eventually resolves later in pregnancy. On ultrasound, it looks like a thick walled complex cyst with blood flow around it. The main consideration becomes an ectopic pregnancy although this is rare in the ovary.
The treatment of ectopic pregnancy can be both medical and surgical. Medical treatment involves giving a medicine called methotrexate. Surgical treatment involves removing the tube with the ectopic. Rupture of an ectopic pregnancy can be life threatening because of bleeding. Early diagnosis of an ectopic pregnancy is therefore crucial to prevent complications.