The Rapid Review series reviews the key points of a clinical review paper. The current topic: Ovarian hyperstimulation syndrome (OHSS)
What is it?
During assisted reproduction, exogenous hormones are administered to stimulate ovarian follicle production. Ovarian hyperstimulation syndrome is an abnormally excessive response to this ‘controlled ovarian stimulation’. OHSS occurs in 30% of assisted reproductive cycles, with severe OHSS occuring in 1-5% of cycles. Risk factors include younger age, polycystic ovarian syndrome, and previous OHSS.
What is the pathophysiology?
The three main components of OHSS are:
- Vasodilation and capillary permeability: Fluid shifts from the intravascular to extravascular space, resulting in intravascular fluid depletion and ascites. The uterus and ovaries enlarge. Ovarian cysts may rupture or haemorrhage. In severe cases, increased intra-abdominal fluid can result in abdominal compartment syndrome, with associated liver injury and AKI.
- Hypercoagulability: Hemoconcentration results in hypercoaguability, leading to venous or arterial thromboembolism in 10% of severe OHSS cases.
- Immunodeficiency: Protein losses results in decreased levels of IGA and IGG, increasing patients’ risk of infection.
What are the presenting symptoms?
In mild cases, patients present with abdominal distension, abdominal pain, and weight gain. This can be followed by vomiting and diarrhea.
In severe OHSS patients may become hemodynamically unstable secondary to intravascular fluid depletion, GI losses, and other complications (cardiac tamponade, septic shock, hemorrhagic ovarian cyst). They may be profoundly dsypneic due to pleural effusions, ARDS, or pulmonary embolism.
Patients often have a fever secondary to an inflammatory state, but may not always have a clear infectious source.
What is the workup?
- Physical exam: In addition to a cardiac, respiratory, and abdominal/pelvic exam, weight and abdominal girth can be measured and compared to previous values.
- Labs: Basic metabolic panel, VBG, serum osmolality, lactate, LFTs, bilirubin, ALP, albumin, INR/PTT, fibrinogen, bHCG
- Imaging: At a minimum, an ultrasound is required to visualize ovarian size and rule out alternative causes for abdominal pain and distension.
Based on the patient’s presentation, a type and screen, infectious workup, and further imaging can be considered.
What is the management?
OHSS is self-limited and management is supportive. Mild cases can be managed as an outpatient (after discussing the patient with OBGYN). In severe cases, involve your obstetrical colleagues early. Initiate fluid resuscitation with intravenous crystalloid. Manage respiratory distress with supplemental oxygen, non-invasive ventilation, or intubation as required. Correct electrolyte abnormalities and consider paracentesis for symptom relief. In patients with possible sepsis, start empiric antibiotics with a third or fourth generation cephalosporin plus metronidazole.
Noren Khamis. Ovarian hyperstimulation syndrome: a rapid review, First10EM, 2019. Available at: