Whether pulmonary embolism in patients with the nephrotic syndrome is caused by deep venous thrombosis or renal vein thrombosis is controversial. To determine which is the likely cause of pulmonary embolism in patients with the nephrotic syndrome, we investigated data from the National Hospital Discharge Survey.

The number of patients discharged from nonfederal short-stay hospitals in the United States with a diagnostic code of nephrotic syndrome, deep venous thrombosis, renal vein thrombosis, and pulmonary embolism was obtained using ICD-9-M (International Classification of Diseases, Ninth Revision, Clinical Modification) codes.

From 1979 to 2005, 925,000 patients were discharged from hospitals with the nephrotic syndrome and 898,253,000 patients did not have the nephrotic syndrome. With the nephrotic syndrome, 5000 (0.5%) had pulmonary embolism, 14,000 (1.5%) had deep venous thrombosis, and fewer than 5000 had renal vein thrombosis. The relative risk of pulmonary embolism comparing patients with the nephrotic syndrome to those who did not have it was 1.39, and the relative risk of deep venous thrombosis was 1.72. Among patients aged 18-39 years, the relative risk of deep venous thrombosis was 6.81. From 1991-2005, after venous ultrasound was generally available, the relative risk of deep venous thrombosis (all ages) was 1.77.

The nephrotic syndrome is a risk factor for venous thromboembolism. This is strikingly apparent in young adults. Renal vein thrombosis was uncommon. Therefore, pulmonary embolism, if it occurs, is likely to be due to deep venous thrombosis and not renal vein thrombosis.