Teaching Case

A 37-year-old female who was 14 weeks gestation presented with severe symptomatic hypertension (200/98). The current pregnancy was initiated with assisted fertility in the form of in-vitro fertilisation (IVF). Treatment was initiated according to the Royal College of Obstetricians and Gynaecologists (RCOG) guidelines with a combination of labetalol, methyldopa and hydralazine. Treatment with spironolactone was contra-indicated due to the risk of ambiguous genitalia in foetus[1]. The patient had no previous history of hypertension. Targets biochemical blood and urine markers were performed to search for a cause of secondary hypertension.

Renal ultrasound was unremarkable. The kidneys demonstrated normal bipolar length, cortico-medullary echogenicity and vascularity on colour doppler with no evidence of solid or cystic lesion, calculus or hydronephrosis.

Pelvic ultrasound (figure 1 and 2) demonstrated a predominantly solid right ovarian lesion with a central cystic area measuring 6.4 x 6 x 6.3 cm. The non-cystic area was heterogeneously hyperechoic. Colour doppler examination demonstrated peripheral hypervascularity.

On Magnetic Resonance Imaging (MRI) the appropriate size-for-dates gravid uterus was unremarkable. The ultrasound identified right ovarian lesion was again demonstrated and characterised as a well-circumscribed mass measuring 6.4 X 6.2 X 6.7 cm (AP, TR, CC) (figure 3 and 4), iso-hypointense relative to adjacent myometrium and discrete from the uterus on T1-weighted sequence. On T2-weighted sequence there was central hyperintensity with a surrounding thick wall of hypointensity and a hyperintense rim (figure 4).

There was no structural abnormality identified in the left ovary. Additionally, the bilateral adrenal glands and kidneys, liver, spleen, and pancreas appeared normal. 

The ultrasound and MRI pattern were suggestive of a corpus luteal cyst.

Background

The corpus luteum usually regresses spontaneously following the first trimester, when pregnancy has occurred. A corpus luteal cyst is a functional ovarian cyst which occurs when the corpus luteum fails to regress following release of ovum and continues to grow[2]. The luteal cyst that develops may be filled with either fluid or blood, referred to as a corpus luteum cyst and haemorrhagic corpus luteum, respectively[2]. A 3-cm threshold has been suggested to differentiate follicles, and A corpus luteum cyst is differentiated from luteal cysts based on their size, with the later greater than 3 cm[2].

Clinical Perspective

The presentation of acute gestational hypertension in the first and second trimesters is generally due to primary hypertension (>90%). However, secondary hypertension should be considered in those whose hypertension is severe/resistant, with a maternal age under 35 years, no family history or with suggestive laboratory findings of a secondary cause (increased creatinine or hypokalaemia)[3]. Secondary causes of hypertension in pregnancy include renovascular hypertension, chronic kidney disease, phaeochromocytoma, Cushing syndrome and primary aldosteronism[4]. The renin-angiotensin-aldosterone system (RAAS) is involved in maintaining blood volume and pressure whilst additionally playing a role in oocyte maturation and ovulation[5]. Biochemical assessment highlighted hyperaldosteronism with elevated renin, suggestive of a secondary aetiology. Imaging was necessary to identify potentially treatable and out rule sinister aetiologies, including ovarian cyst rupture or malignancy, which would require surgical investigation and treatment[3,4].

Imaging Perspective

On ultrasonography, luteal cysts can vary in appearance based on the phase of development and presence and timing of intracystic haemorrhage. Typical characteristics include a cyst that is 2-10cm in diameter with peripheral vascularity and a diffusely thickened and crenulated wall[6].

The characteristic MRI appearance of a reproductive female ovary is a homogenous soft-tissue T1-weighted signal intensity, which can be difficult to differentiate from adjacent bowel. Whilst on T2-weighted images, the ovaries characteristically have a low signal intensity cortex and high signal intensity medulla with scattered well-circumscribed fluid foci corresponding to follicles[2].

A corpus luteal cyst on CT is typically identified as a well-demarcated unilocular cystic structure located within the ovary, which is demarcated by a crenulated and signal-enhancing rim. This indicates prominent vascular flow within thickened walls and highlighted by the ‘ring of fire’ sign in colour Doppler US[2]. MRI exhibits a comparable appearance with internal fluid-like hypointense and hyperintense signal on T1- and T2-weighted images, respectively, and significant wall enhancement following gadolinium contrast[7].

Outcome

Biochemical markers highlighted aldosterone level of 1828pg/ml (normal: 67-335) and renin of 1584pg/ml (normal: 5-40) and potassium of 3.2 (normal: 3.5-4.5). The patient was diagnosed with secondary hypertension in pregnancy due to hyperaldosteronism caused by renin secreting corpus luteal cyst diagnosed on imaging. Management of gynaecological emergencies during pregnancy should always be individualised, with management often requiring close monitoring and multidisciplinary discussion. The majority of corpus luteal cysts spontaneously involute at the end of the second trimester[2], when associated with pregnancy[8]. In our case, blood pressure stabilisation was the primary concern. However, surgical intervention with laparoscopy may be necessary for rare instances when the corpus luteal cyst ruptures.

Take Home Message / Teaching Points

• The CT and MRI hallmark of a corpus luteal cyst is a cystic adnexal structure with a crenulated wall and strongly enhancing vascular periphery.
• Secondary causes of hypertension in pregnancy include renovascular hypertension, chronic kidney disease, phaeochromocytoma, Cushing syndrome and primary aldosteronism.
• Secondary aetiologies of gestational hypertension require imaging (ideally MR and ultrasonography) to facilitate prompt treatment given potential maternal and fetal sequelae.