Supplementary Material for: Spontaneous Massive Retroperitoneal Hematoma: A Rare Complication of Anticoagulation after Stenting in Malignant Superior Vena Cava Syndrome

Introduction:
Superior vena cava (SVC) syndrome is a well-recognised complication of thoracic malignancies, most commonly small-cell lung cancer. Endovascular stenting is preferred because it provides rapid symptom relief and restores venous patency. However, the role of post-stenting anticoagulation remains controversial, and complications related to its use are rarely reported. We describe such a case in a patient with malignant SVC syndrome.

Case Presentation:
A 51-year-old woman with small-cell carcinoma of the lung and superior vena cava syndrome underwent stenting of the superior vena cava. After the procedure, she was on prophylactic low-molecular-weight heparin and developed a large retroperitoneal hematoma with a significant decrease in haemoglobin on day four. The patient was managed with a transfusion and conservative care. Massive retroperitoneal hematomas secondary to anticoagulation therapy after superior vena cava stenting are highly uncommon.
Conclusion:
There is currently no consensus guideline on post-stenting anticoagulation in malignant superior vena cava syndrome. This case highlights one of the problems encountered in the post-stenting scenario of malignant SVC syndrome.