Sonographic spectrum of the corpus luteum in early pregnancy: gray-scale, color, and pulsed Doppler appearance.

Abstract

We describe the gray-scale and Doppler sonographic features of the corpus luteum during the first trimester of pregnancy. Using transvaginal sonography, we prospectively evaluated the ovaries of 160 patients with spontaneous singleton intrauterine gestations between 5 and 8 weeks' menstrual age. Size, sonographic appearance, resistance index, and peak systolic velocity were recorded. The corpus luteum was identified in 157 (98%) of 160 patients. The mean diameter was 1.9 +/- 0.6 cm. The most common appearance was a round hypoechoic structure, found in 54 patients (34%). Other appearances included a cyst with a thick wall and anechoic center (43 patients, 27%), a cyst containing internal debris (36 patients, 23%), and a thin-walled simple cyst (24 patients, 15%). Corpus luteal blood flow was visualized with color Doppler imaging in 92% (145/157) of patients in whom the corpus luteum was found. Color Doppler imaging typically revealed a circumferential rim surrounding part or all of the corpus luteum. Low-resistance blood flow was seen with pulsed Doppler interrogation, with a mean resistance index of 0.49 +/- 0.08 and mean peak systolic velocity of 17 +/- 10 cm/second. The corpus luteum in early pregnancy is routinely identified with transvaginal sonography and has a wide range of sonographic appearances. Recognizing the various appearances of the corpus luteum is important to avoid confusing them with true ovarian abnormalities.