Corpus luteal (CL) cysts are a type of functional ovarian cyst that results when a corpus luteum fails to regress following the release of an ovum. When associated with pregnancy, it is the most common pelvic mass encountered within the 1st trimester. There is also some overlap with the term "haemorrhagic corpus luteum".
The natural history of a normal corpus luteum is to regress by the end of the 1st trimester if pregnancy has occurred. If a corpus luteum fails to regress and instead enlarges with or without haemorrhage, a corpus luteum cyst is formed. There is some overlap in the definitions of a corpus luteum cyst and a haemorrhagic corpus luteum 5.
When associated with pregnancy, most corpus luteal cysts spontaneously involute at the end of the 2nd trimester.
They can have a range of sonographic appearances depending on the stage of evolution and age of the associated intracystic haemorrhage 3. General characteristics include 7:
- diffusely thick wall
- peripheral vascularity
- <3 cm
- possible crenulated contour
If the cyst has been present for some time with complicating haemorrhage, a fine internal lace-like echo-pattern may be seen.
Colour Doppler shows either no vascularity within the cyst or shows low resistance blood flow around the cyst, also known as hypervascular ''ring of fire''.
- low-attenuating cyst (25 HU)
- <3 cm in diameter with thickened walls
- slightly irregular cyst
- iso- or hyperattenuating walls 6
- free fluid is often associated 6
It is often seen as a round or oval adnexal lesion.
- T1: typically homogeneously hypointense 1
- T2: typically hyperintense 1-2
- T1 C+ (Gd): intense wall enhancement may be seen 1
Treatment and prognosis
For a corpus luteal cyst ≤3 cm, no follow up is necessary 7.
It can be difficult to differentiate from a tubal ring in an ectopic pregnancy in some situations, and correct clinical interpretation is often required.
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- 2. Siegelman ES, Outwater EK. Tissue characterization in the female pelvis by means of MR imaging. Radiology. 1999;212 (1): 5-18. Radiology (full text) - Pubmed citation
- 3. Merz E. Ultrasound in obstetrics and gynecology, Gynecology. Thieme Publishing Group. (2007) ISBN:3137544025. Read it at Google Books - Find it at Amazon
- 4. Swire MN, Castro-aragon I, Levine D. Various sonographic appearances of the hemorrhagic corpus luteum cyst. Ultrasound Q. 2004;20 (2): 45-58. Ultrasound Q (link) - Pubmed citation
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- 6. Borders RJ, Breiman RS, Yeh BM et-al. Computed tomography of corpus luteal cysts. J Comput Assist Tomogr. 2004;28 (3): 340-2. Pubmed citation
- 7. Levine D, Brown DL, Andreotti RF et-al. Management of asymptomatic ovarian and other adnexal cysts imaged at US: Society of Radiologists in Ultrasound Consensus Conference Statement. Radiology. 2010;256 (3): 943-54. doi:10.1148/radiol.10100213 - Pubmed citation