A 28-year-old woman comes to the emergency department due to nausea, vomiting, and abdominal pain. For the past 2 days, the patient has had increasing abdominal pain and distension, which are now severe and causing persistent vomiting. She had an episode of watery diarrhea but has had no fevers, chills, or sick contacts. The patient has no chronic medical conditions. She has been undergoing ovulation induction for infertility treatment. Her last hCG injection was 7 days ago, and her last menstrual period was 3 weeks ago. Blood pressure is 100/60 mm Hg, pulse is 104/min, and respirations are 24/min. BMI is 21 kg/m². Cardiac examination reveals sinus tachycardia. The lungs have decreased breath sounds in bilateral bases. The abdomen is distended and has tympany but no rebound or guarding. Laboratory results are as follows: Pelvic ultrasound reveals a small uterus with a thin endometrium, bilateral enlarged ovaries with multiple cysts, and a large amount of free fluid within the abdomen. Which of the following is the most likely diagnosis in this patient?

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11ec25c8_da42_076b_bc81_e9a56eb7b086_MD0003_00 This patient has ovarian hyperstimulation syndrome (OHSS), a rare but life-threatening complication of ovulation induction. Ovulation trigger agents (eg, hCG injection) stimulate artificial maturation of multiple ovarian follicles in patients undergoing infertility treatment and can cause an exaggerated ovarian response (eg, bilateral enlarged, cystic ovaries with multiple follicles) as well as overexpression of vascular endothelial growth factor (VEGF), causing increased vascular permeability and capillary leakage. This causes massive extravascular fluid shifts (eg, third spacing) and VEGF leakage into the intraperitoneal cavity, leading to ascites and abdominal distension. Affected patients typically develop OHSS 1-2 weeks after ovulation induction. Symptoms include nausea, vomiting, and abdominal pain. Other features include pleural effusions (eg, tachypnea, decreased breath sounds) and intravascular volume depletion (eg, tachycardia, hemoconcentration, leukocytosis) due to third spacing, which in severe cases can result in thromboembolism, renal failure, and death. (Choice A) Drug-induced anaphylaxis can present with shock and third spacing due to massive mast cell degranulation. However, symptom onset is typically within minutes; this patient's hCG injection was 7 days ago. In addition, patients with anaphylaxis typically have skin changes (eg, hives) or bronchospasm (eg, wheeze), not ascites or bilateral enlarged, cystic ovaries. (Choice B) An ectopic pregnancy can present with pain, abdominal free fluid, and a positive β-hCG test; however, patients have unilateral adnexal findings (eg, hypervascular mass) and anemia rather than bilateral adnexal cysts and hemoconcentration. This patient's β-hCG level is due to recent hCG injection, not pregnancy. (Choice C) Epithelial ovarian cancer can cause abdominal pain, ascites, and distension. However, patients typically have gradual onset of symptoms and a unilateral adnexal mass, not bilateral enlarged, cystic ovaries. (Choice D) A hydatidiform mole can cause bilateral ovarian cysts (ie, theca lutein cysts) and a positive β-hCG test; however, patients typically have a markedly enlarged uterus (size > gestational age). This patient has a small uterus with a thin endometrial lining. (Choice F) Polycystic ovary syndrome can cause infertility and bilateral ovarian cysts. However, it does not cause acute third spacing (eg, ascites) or intravascular volume depletion (eg, hemoconcentration). Polycystic ovary syndrome Educational objective: Ovarian hyperstimulation syndrome is a complication of ovulation induction for infertility treatment. Patients develop symptoms within 1-2 weeks that include abdominal pain; ascites; bilateral enlarged, cystic ovaries; and third spacing leading to intravascular volume depletion (eg, hemoconcentration). Severe complications include thromboembolism, multiorgan failure, and death. References: Ovarian hyperstimulation syndrome management strategies: where are we going? (http://www.ncbi.nlm.nih.gov/pubmed/28322539) Pathophysiology, treatment and prevention of ovarian hyperstimulation syndrome. (http://www.ncbi.nlm.nih.gov/pubmed/27273307)

A 28-Year-Old Woman Comes to the Emergency Department Due to Nausea