Corpus luteal cysts are the second most common type of functional ovarian cyst and arguably the most clinically significant.
The corpus luteum develops from a mature graafian follicle during the luteal phase of the reproductive cycle. Following ovulation, vascularization of the follicle produces limited, spontaneous bleeding into its core. If bleeding persists, expansion of the corpus (> 3cm diameter) results in a luteal cyst.

Patients with symptomatic luteal cysts present with complaints related to pelvic pain or mass or due to hormonal effects. Physiologically active, functional, luteal cysts produce progesterone with associated changes in menstruation; typically delayed menses with subsequent menorrhagia. The classic triad of a functional symptomatic cyst was described by Halban and consists of:

>> delayed menses followed by spotting
>> unilateral pelvic pain
>> tender adnexal mass

The symptoms of this triad are virtually indistinguishable from those of an ectopic pregnancy except for the abscence of an elevated BHCG level.

Ultrasound findings in uncomplicated luteal cysts are a vascular periphery with a doppler “Ring” color flow pattern, an echogenic, crenulated wall, and a hypoechoic core.

Corresponding CT findings for these cysts are a thick, crenulated, hyperdense wall with hypodense core. Small amounts of free intraperitoneal fluid may be visualized even in the absence of frank cyst rupture.

Rupture of a luteal cyst can result in a spectrum of bleeding with massive hemoperitoneum being more common in the setting of bleeding diasthesis or anti-coagulation. Patients present with severe, acute unilateral pelvic pain (right>left 2:1) often following minor trauma, coitus, exercise, or pelvic examination.

Radiologic features of a ruptured luteal cyst are dominated by hemoperitoneum. Differentiation from a ruptured ectopic pregnancy are based on correlation with BHCG levels. Surgical exploration may be required.

REFERENCES:
>>Haaga JR. CT and MRI of the Whole Body, third ed. St Louis: Mosby, 1994.
>>Meire HB. Clinical Ultrasound: a comprehensive text. London: Churchill Livingstone, 2001.
>>Schwartz GR. Principles and Practice of Emergency Medicine, fourth ed. LWW, 1999.
>>Stenchever MA. Comprehensive Gynecology, forth ed. St Louis: Mosby, 2001.
>>Chapman S. Aids to Radiologic Differential Diagnosis, third ed. London: Saunders, 1995.
>>Borders RJ et al: Computed Tomography of Corpus Luteal Cysts. J Computer Assisted Tomography. 28(3):340-342, May/June 2004.
>>Hertzberg BS et al: Ovarian cyst rupture causing hemoperitoneum: imaging features and potential for misdiagnosis. Abdominal Imaging. 24:304-308, May/June 1999.