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Ovarian vein thrombosis (OVT) is an uncommon entity typically seen in the post-partum, patients with pelvic surgery, infection, or inflammation, and hypercoagulabilty. Concurrent pulmonary embolism (PE) may occur in these patients; however, is an uncommon complication. Treatment commonly involves anti-coagulation and antibiotics in the setting of pelvic inflammatory disease. Presented is a case report of ovarian vein thrombosis leading to pulmonary embolism in the setting of malignancy, underscoring the importance of inspecting the gonadal vein during interpretation, particularly in the emergency setting.
A 69 year old woman with metastatic pancreatic cancer to liver and spine on chemotherapy presents for routine imaging followup. Incidental thrombus was seen in the right ovarian vein (figures 1 and and2).2). Additional incidental subtle thrombus was seen in the right inferior pulmonary artery branch (figure 3). A four month prior exam demonstrated a normal appearance of the ovarian vein (figures 4 and and5)5) without pulmonary embolism (not shown). The patient had no symptoms referable to pulmonary embolism. The referring clinician was immediately notified and the patient started on anticoagulation. Routine 3 month follow up scan demonstrated resolution of the right ovarian vein thrombus (figure 6) and pulmonary embolism (not shown).
Pulmonary embolism has an incidence of 1 in 1000 persons per year in the United States, for about 250,000 incident annual cases . Early detection and treatment with anticoagulation is critical to decrease morbidity and mortality . Ovarian vein thrombosis (OVT) causing pulmonary embolism is rare event, with limited etiologies such as postpartum endometritis, post gynecological surgery, pelvic inflammatory disease, and hypercoagulable states such as malignancy .
The ovarian veins originate from a venous plexus near the ovary and fallopian tubes and course over the psoas muscle and ureters. The right ovarian vein drains into the inferior vena cava and left renal vein on the left . They normally measure about 3–4 mm in diameter . The vein can be easily visualized at the level of the inferior mesenteric artery as it is surround by fat. .
A thrombosed ovarian vein will be dilated with central hypodensity and peripheral hyperdensity or targetoid appearance on post contrast CT imaging. The sensitivity of contrast enhanced CT to detect OVT approaches 100% although may be overlooked by the inexperienced radiologist given infrequent presentation . Differential of a filling defect on CT would include admixture flow artifact from unopacified blood mixing with opacified blood. This is commonly seen in the femoral veins and inferior vena cava. To our knowledge, on noncontrast imaging, the vein may be normal caliber or expanded, depending on clot burden. The thrombus would likely be isodense and difficult to impossible to visualize without contrast.
Pregnancy, being the commonest cause for OVT, occurs with an incidence of 0.05% to 0.018% after vaginal birth and up to 2% after cesarean section . 80–90% of ovarian vein thrombosis will occur on the right side. This is thought to occur due to mass effect from the gravid uterus causing stasis . Thrombus may then embolize to the lungs, being potentially fatal, hence close attention to this location is highly important. The risk of embolization has been estimated to be approximately 13% in one study . To our knowledge, this is the only recent study that quantifies the risk of embolism. These patients may present with right lower quadrant pain and fever .
Other less common causes include pelvic inflammatory disease, post pelvic surgery, or hypercoagulablity from, for example, malignancy and hematological disorders . These patients will present with the symptoms respective to the disease process. OVT may be asymptomatic as some patients who have undergone hysterectomy. Study by Yassa et al  followed 50 patients after total abdominal hysterectomy and bilateral salpingo-oophorectomy who developed OVT, 75% involving the right ovarian vein. None of these patients developed pulmonary embolism, even after 2 years of followup .
OVT can be incidentally identified on imaging for other indications, as in our case, for routine malignancy followup. One series by Jacoby et al , followed 6 oncology patients with gonadal vein thrombosis; four with metastatic breast cancer, one with metastatic pancreatic cancer, and one with metastatic adenocarcinoma of unknown primary. These patients did not get anticoagulation nor developed pulmonary embolism. In three patients, thrombosis persisted for up to one year without symptoms .
Ovarian vein thrombosis is usually treated with antibiotics and anticoagulation given OVT usually occurs in the setting of post-partum endometritis. Although risk for pulmonary embolism is low, these patients are at most risk [7–9]. Treating OVT in the setting of malignancy is debatable without clear evidence for benefit from anticoagulation [10–11]. OVT after hysterectomy is unlikely to be treated given its appearance as a common post-surgical finding .
Ovarian vein thrombosis is a rare, yet highly important, entity to recognize, due to possibility of causing pulmonary embolism. Inspection of ovarian veins should be part of every CT interpretation, particularly in the setting of pregnancy, malignancy, pelvic infection and surgery, as a small clot may be overlooked.