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

Purpose. We describe the gray-scale and Doppler sonographic features of the corpus luteum during the first trimester of pregnancy. Methods. Using transvaginal sonography, we prospectively evaluated the ovar ies of 160 patients with spontaneous singleton intrauterine gestations betw een 5 and 8 weeks' menstrual age. Size, sonographic appearance, resistance index, and peak systolic velocity were recorded. Results. 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 h ypoechoic structure, found in 54 patients (34%). Other appearances included a cyst with a thick wall and anechoic center (43 patients, 27%), a cyst co ntaining internal debris (36 patients, 23%), and a thin-walled simple cyst (24 patients, 15%). Corpus luteal blood flow was visualized with color Dopp ler imaging in 92% (145/157) of patients in whom the corpus luteum was foun d. Color Doppler imaging typically revealed a circumferential rim surroundi ng part or all of the corpus luteum. Low-resistance blood flow was seen wit h pulsed Doppler interrogation, with a mean resistance index of 0.49 +/- 0. 08 and mean peak systolic velocity of 17 +/- 10 cm/second. Conclusions. The corpus luteum in early pregnancy is routinely identified w ith 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. (C) 1999 John Wiley & Sons, Inc.