Positron emission tomography reveals a leiomyosarcoma causing proteinuria

Obstruction of the renal veins may result in proteinuria and is frequently caused by thrombosis or tumorous processes. Since thrombosis and malignancy may occur simultaneously in the venous outflow of the kidneys, search for an underlying intraluminal tumor may be impeded by extensive thrombosis in the lumen of renal and caval veins. We report the case of a 30-year-old man with moderate proteinuria which was caused by an obstructing process of the vena cava inferior and the renal veins. While the obstructive mass was initially misdiagnosed as thrombosis, positron emission tomography helped to reveal the tumorous character of the lesion and fine-needle biopsy allowed rapid diagnosis of a leiomyosarcoma originating from the caval or renal veins. We conclude that undelayed diagnosis of the cause of renal and caval vein obstruction is facilitated by early positron emission tomography and subsequent fine-needle biopsy to identify possible tumorous lesions.