Emergent complications of assisted reproduction: expecting the unexpected.

With the increasing popularity of assisted reproductive technology (ART), radiologists are more likely to encounter associated complications, especially in an emergency setting. These complications include ovarian hyperstimulation syndrome (OHSS), ovarian torsion, and ectopic and heterotopic pregnancy. OHSS occurs following ovulation induction or ovarian stimulation and manifests with bilateral ovarian enlargement by multiple cysts, third-spacing of fluids, and clinical findings ranging from gastrointestinal discomfort to life-threatening renal failure and coagulopathy. Enlarged hyperstimulated ovaries are at risk for torsion. Clinical symptoms are often nonspecific, and ovarian torsion should be suspected and excluded in any female patient undergoing infertility treatment who presents with severe abdominal pain. The most consistent imaging finding is asymmetric enlargement of the twisted ovary. There is also an increased risk for ectopic pregnancy following ART, with a relative increased risk for rarer and more lethal forms, including interstitial and cervical ectopic pregnancies. Heterotopic pregnancy refers to simultaneous intrauterine and ectopic pregnancies and has an incidence of 1%-3% in ART patients. Careful evaluation of the adnexa is critical in this patient population, even when an intrauterine pregnancy has been confirmed. Ultrasonography is the first-line imaging modality for the evaluation of complications of ART, although nonspecific symptoms may sometimes lead to cross-sectional imaging being performed. Familiarity with the multimodality imaging appearance of these entities will allow accurate and timely diagnosis and help avert potentially fatal consequences.