Ovarian hyperstimulaiton syndrome (OHSS) is a relatively uncommon complication of fertility treatment. The true incidence is unknown. It results from an excessive ovarian response to stimulation by follicle stimulating hormone (FSH), with subsequent responses to human chorionic gonadotrophin (hCG) and/or luteinising hormone (LH).
Pathophysiology
The action of hCG on hyperstimulated ovaries causes a release of proinflammatory cytokines. Vascular endothelial growth factor (VEGF) increases vascular permeability and leads to loss of fluid into the “third space”; this commonly manifests as ascites. The reduction in intravascular fluid volume produces a hypovolaemia with haemoconcentration and paradoxical hypoösmolality.
The life threatening complications such as acute respiratory distress syndrome (ARDS), renal failure, and thrombosis result from the disturbed physiology: third spacing, hypovolaemia, and proimflammatory/prothrombotic state (or perhaps hyperviscosity) respectively. Severe ovarian haemorrhage may also occur as a result of ovarian rupture.
Signs and symptoms
- Abdominal pain, bloating
- Nausea and vomiting
- Breathlessness
- Reduced urine output
- Oedema, particularly lower limbs and vulval
Relevant investigations
- Full blood count
- Renal function test (electrolytes)
- CRP
- Serum osmolality
- hCG
- Liver function test
- Coagulation studies
Management
For the most part, cases of mild to moderate OHSS can be managed in the outpatient setting. Admission is probably only necessary for severe cases where the patient is (or may become) unstable, when pain or fluid balance cannot be managed adequately, or if regular outpatient follow up for monitoring is difficult.
Supportive management is primarily analgesia and maintaining fluid intake. Nonsteroidal antiinflammatory drugs should be avoided on account of their renal effects. Antiemetics may also be required. Oral rehydration is the rule because the lack of research leaves us with Nature’s methods; also, large volumes of crystalloids will probably leave the intravascular space on account of the whole “third spacing” business. They are reasonable for initial management of the haemoconcentration. Colloids have theoretical advantages but are outside my scope.
Drainage of ascitic fluid should be considered for symptom management where the ascites is significant. There is talk that it may also improve disease progression where the intraäbdominal pressures are high..
Also outside my scope is the management of most of the elements of critical OHSS. ICU admission may be warranted if the wheels are falling off and surgical management may be required for more secondary complications such as ovarian torsion.
Further reading
- Marthur R, Drakeley A, Raine-Fenning N, Evbuomwan I, Hamoda H. The Management of Ovarian Hyperstimulation Syndrome. Green Top Guideline No. 5. London: Royal College of Obstetricians and Gynaecologists; 2016.