A 31-year-old woman undergoing controlled ovarian stimulation for IVF received hCG trigger 9 days ago. She now presents with progressive abdominal distension, severe nausea, vomiting, reduced urine output, and dyspnea. Examination reveals tense abdominal distension with shifting dullness, bilateral basal crackles, hypotension (96/64), tachycardia (116 bpm), hematocrit 53%, WBC 22,000, creatinine 1.6 mg/dL, and hyponatremia. Ultrasound shows the structure marked **A** measuring >12 cm bilaterally with multiple large cysts in a wheel-spoke pattern, along with ascites and pleural effusions. Which of the following best explains the pathophysiology of the severe manifestations in this patient?
A. VEGF-mediated increased capillary permeability leading to intravascular-to-third-space fluid shift, hemoconcentration, and end-organ hypoperfusion
B. Direct mechanical compression of the inferior vena cava by enlarged ovaries causing venous stasis and thromboembolism
C. Estrogen-induced hepatic synthesis of clotting factors leading to disseminated intravascular coagulation
D. Bacterial translocation from the bowel due to ovarian enlargement causing septic shock and multi-organ failure
Explanation
Why VEGF-mediated increased capillary permeability is right
The structure marked A — the enlarged multicystic ovary — is the source of VEGF release from granulosa cells in response to exogenous hCG trigger. This VEGF causes increased capillary permeability, leading to intravascular-to-third-space fluid shift. This pathophysiology explains all the clinical findings in this patient: ascites and pleural effusions (third-space fluid), hemoconcentration (hematocrit 53%), hyponatremia and hyperkalemia (fluid redistribution), oliguria and renal dysfunction (hypovolemia and hypoperfusion), and the tense abdominal distension. This is the established mechanism of OHSS according to ESHRE/ASRM and RCOG guidelines.
Why each distractor is wrong
Direct mechanical compression of the inferior vena cava: While enlarged ovaries may cause some mechanical effects, the primary pathophysiology of OHSS is not mechanical compression but rather VEGF-mediated capillary leak. Mechanical compression would not explain the hemoconcentration, hyponatremia, or the systemic inflammatory response.
Bacterial translocation and septic shock: There is no evidence of infection in this case (no fever, no positive cultures implied). The elevated WBC is a response to OHSS itself, not sepsis. The clinical picture is consistent with hypovolemic shock from third-space loss, not septic shock.
Estrogen-induced hepatic synthesis and DIC: While estrogen is elevated in ovarian stimulation, DIC is not the primary mechanism of OHSS. The INR is only mildly elevated (1.4), and there is no evidence of microangiopathic hemolytic anemia or platelet consumption typical of DIC.
High-YieldNEET PG
OHSS pathophysiology is VEGF-mediated capillary leak from enlarged ovaries → third-space fluid shift → hemoconcentration, ascites, pleural effusion, and end-organ hypoperfusion.
ESHRE/ASRM OHSS Guideline; RCOG Green-top Guideline No 5
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