New Nephrotic Syndrome With Acute DVT: Anticoagulate Now or Wait for the Kidney Biopsy?
Mr. H is a 55-year-old man with new nephrotic syndrome. He has periorbital and bilateral leg edema, weight gain of 6 kg in 3 weeks, and a serum albumin of 2.0 g/dL. Urine protein-to-creatinine ratio is 9,800 mg/g; creatinine 1.1 mg/dL; cholesterol 340 mg/dL. He has no known diabetes. He reports a swollen, painful left calf for 2 days. His only medication is furosemide 40 mg daily. BP 138/84, HR 88, afebrile. Ultrasound shows a non-occlusive left popliteal vein thrombosis. A kidney biopsy is scheduled in 3 days. He has a history of a remote upper GI bleed 8 years ago after NSAID use. He asks whether he should start a blood thinner today and whether the biopsy must be canceled.
1. How would you evaluate his venous thrombosis risk and decide on anticoagulation before the biopsy diagnosis is known?
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This is nephrotic syndrome with albumin 2.0 g/dL and a confirmed acute popliteal DVT. The risk of venous thromboembolism is high with albumin below 2.5 g/dL, and a confirmed proximal DVT is generally an indication for therapeutic anticoagulation even before the biopsy diagnosis is known. His GI bleed is remote and not active, so it is not an absolute contraindication. I would check platelets, renal function, and bleeding risk, then start anticoagulation and coordinate timing with the biopsy team. A shorter-acting agent such as LMWH can be held per protocol before biopsy. An IVC filter is reserved for active bleeding or inability to anticoagulate. I would not reflexively cancel the biopsy, but I would not perform it while he is fully anticoagulated.
2. What is the appropriate workup for the underlying glomerular disease, and which serologies would you send?
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A kidney biopsy is essential for diagnosis and to guide immunosuppression. Before biopsy, send anti-PLA2R antibody because membranous nephropathy is a leading cause of nephrotic syndrome with thrombosis; also send ANA, anti-dsDNA, complement C3 and C4, hepatitis B and C, HIV, cryoglobulins, serum protein electrophoresis with free light chains, and age-appropriate malignancy screening. Check glucose or HbA1c to exclude diabetes. The combination of nephrotic syndrome and DVT strongly suggests membranous nephropathy, but other causes remain possible. Do not delay treatment of the DVT while serologies are pending.
3. Outline first-line management of his nephrotic syndrome and the safety monitoring you would use.
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Treat the DVT with therapeutic anticoagulation. Reduce edema with sodium and fluid restriction and loop diuretics, monitoring renal function and potassium. Use an ACE inhibitor or ARB if BP tolerates for antiproteinuric effect, add a statin for hyperlipidemia, and consider vitamin D and calcium. For membranous nephropathy, risk-stratify using PLA2R antibody level and proteinuria: supportive care for low risk, immunosuppression such as rituximab or cyclophosphamide plus steroids for high risk. Monitor creatinine, potassium, albumin, proteinuria, volume status, and bleeding on anticoagulation. Avoid NSAIDs and nephrotoxins, and involve pharmacy for anticoagulant dosing and interactions.