Images Genevieve Carbonatto
A 7 week pregnant patient presents with acute onset abdominal pain. She has not had a scan before. Her scans show a large CL cyst, a small amount of fluid in the pouch of Douglas and an intrauterine pregancy
Longitudinal view through pelvis. Large CL cyst seen superior to bladder, small amount of fluid in POD Cyst measures 4.06 cm X 3.88 cm. Gestational sac just visible inferior to cyst
CL cyst, small amount of fluid in POD and intrauterine gestational sac in transverse view
The corpus luteum continues to produce these hormones and maximises the chance of implantation into the endometrium in early pregnancy. It reaches a maximum size at ~10 weeks and finally resolves at around 16-20 weeks. Sonographically it has a characteristic “ring of fire ” with Doppler ultrasound and usually a crenulated inner edge and inner echos. It is difficult to differentiate a CL cyst from an ectopic pregnancy. The two structures can be similar in appearance but can be differentiated in the following way : The CL cyst is eccentrically placed within a border of normal ovarian tissue, the tubal ring , in contrast , in a central hypoechoic fluid within a mass of echogenic trophoblastic material (the bagal sign). Both with Colour Doppler demonstrate a “ring of fire”. The CL is ipsilateral to the ectopic pregnancy in 70% of cases. Rupture of a CL cyst may mimic a ruptured ectopic pregancy.
- Clinical Ultrasound : Paul Allan