A 32 year old female presents with pelvic pain, low back pain, and a sensation of "pulling" or "stretching" in her groin. Bimanual examination reveals a firm mass in the right adnexa. An ultrasound examination reveals the presence of fluid in the abdominal cavity and the right thoracic cavity. Which of the following conditions is most strongly suggested by this patient's presentation?

Meigs syndrome is the unusual combination of hydrothorax (often right sided), ascites, and an ovarian tumor (often a benign fibroma). Low back pain and a stretching or pulling sensation are characteristic of ascites in some patients (ascites can also be asymptomatic). The etiology of the fluid accumulation in Meigs syndrome remains a mystery. Ectopic pregnancy would not be associated with hydrothorax. If an ectopic pregnancy ruptured, blood could accumulate in the abdominal cavity, but the patient would likely be hypotensive or dead. An endometrial implant could cause pain, or impair feility, but would not be expected to produce the combination of ascites and isolated right-sided hydrothorax. Pelvic inflammatory disease would be unlikely to produce the combination of ascites and isolated right-sided hydrothorax, although it might cause low back pain or pelvic pain. Ref: Hoffman B.L., Schorge J.O., Schaffer J.I., Halvorson L.M., Bradshaw K.D., Cunningham F.G., Calver L.E. (2012). Chapter 9. Pelvic Mass. In B.L. Hoffman, J.O. Schorge, J.I. Schaffer, L.M. Halvorson, K.D. Bradshaw, F.G. Cunningham, L.E. Calver (Eds), Williams Gynecology, 2e.