Severe ovarian hyperstimulation syndrome during early pregnancy

Clinical History

An infertile woman with otherwise unremarkable medical history presented to the emergency department suffering from abdominal distension, nausea and dyspnoea two weeks after in vitro fertilization with embryo-transfer. Physical examination revealed distended non-tender abdomen, lung base hypoventilation and peripheral oedema. Laboratory tests disclose haemoconcentration, mild hypokalemia and increased transaminase levels.

Imaging Findings

The attending gynaecologist confirmed successful pregnancy initiation including transvaginal sonographic visualization of the gestational sac (not shown), and requested ultrasound assessment of abdomen (Fig.1) and thorax (Fig.2). Both ovaries were symmetrically enlarged (7.5x5.2 cm approximate diameters) due to multiple anechoic cysts measuring up to 3.5 cm in size. Massive ascites was present, without appreciable abnormalities of the abdominal organs. Furthermore, abundant anechoic pleural effusion was detected bilaterally, with associated parenchymal atelectasis at the lung bases.

These findings were interpreted as consistent with clinical diagnosis of severe ovarian hyperstimulation syndrome during early pregnancy, which was treated medically. Progressive improvement in clinical conditions allowed an uneventful pregnancy course and discharge after 25 days of hospitalization. Meanwhile, ultrasound follow-up (Fig.3) showed complete resolution of pleural effusion, decreased ascites, decreased ovarian volume by approximately 40% with reduced number and size of cysts.

Discussion

Ovarian hyperstimulation syndrome (OHSS) occurs during the luteal phase of the menstrual cycle or sometimes in early pregnancy as an iatrogenic complication of fertility medications to induce ovarian stimulation or ovulation induction. The pathogenesis involves increased ovarian angiogenesis in response to gonadotropins and amplified luteinizing hormone response leading to increased vascular permeability in ovarian vessels [1].
OHSS couples bilateral, often massive ovarian enlargement with multiple cysts coupled with acute fluid shift from the intravascular compartment into the peritoneal and/or pleural cavities. Commonly observed (in 20-33% of patients after hCG stimulation for in-vitro fertilization), mild OHSS is a self-limiting condition which typically resolves within 1-2 weeks. Moderate disease (reported in 3-6% of cases) corresponds to ascites and significantly enlarged (over 6 cm) ovaries. As this case exemplifies, the rare (0.1-2%) severe OHSS needs intensive in-hospital treatment, is potentially life-threatening and includes pleural effusions, respiratory impairment, haemoconcentration, thrombosis, renal failure, hypovolemia or shock [1-3].
Due to the increasing use of assisted reproduction, clinicians and radiologists may be faced with suspected complications which may prove challenging to diagnose. Among these, the commonest occurrences include OHSS, ovarian torsion, ectopic and heterotopic pregnancies in descending order of frequency. Since clinical manifestations are variable and nonspecific, OHSS should be suspected when a female undergoing infertility treatment presents with abdominal pain and gastrointestinal discomfort [2, 3].
During pregnancy ultrasound represents the preferred first-line diagnostic modality, in order to obviate both ionizing radiation exposure and use of magnetic resonance imaging (MRI) during the first trimester. The usual imaging findings include ascites, sometimes pleural effusions, and bilateral symmetrically enlarged multicystic ovaries, containing multiple variable-sized fluid lesions representing enlarged follicles or corpus luteum cysts in a characteristic peripheral location, which may reach a “spoke-wheel” appearance corresponding to centrally located stroma surrounded by large peripheral cysts. Imaging supports the diagnosis by demonstrating rapid resolution of changes during supportive treatment [1-3].
The differential diagnosis encompasses polycystic ovary syndrome, infectious tumour-like lesions and cystic adnexal neoplasms. Ovarian oedema from intermittent impaired blood flow and acute ovarian torsion may clinically mimic OHSS and are significantly more frequent in assisted pregnancies, since large cysts may become a lead point for vascular pedicle twisting. At imaging, torsion should be suggested over OHSS on the basis of unilateral ovarian enlargement and medialization with small cysts and heterogeneous stroma due to haemorrhage and oedema [2, 3].

Differential Diagnosis List

Final Diagnosis

Severe ovarian hyperstimulation syndrome during early pregnancy

URL:	https://www.eurorad.org/case/11952
DOI:	10.1594/EURORAD/CASE.11952
ISSN:	1563-4086