How is myeloma cast nephropathy treated?
Myeloma cast nephropathy is a medical emergency and requires immediate diagnosis and early institution of therapy to prevent irreversible kidney failure. There are two key treatment strategies.
• The first is to remove any precipitants (e.g., sepsis, non-steroidal antiinflammatory drugs, hypercalcemia) and increase urine flow to reverse or prevent oliguria. The toxicity of LC in the tubules in part relates to their concentration, and increasing tubular flow reduces this. Volume expansion with normal saline (or sodium bicarbonate in the presence of acidosis) and the maintenance of a high urine flow (ideally 3 L a day) with adequate oral fluids are required. The reversal of hypercalcemia with volume expansion and bisphosphonates with reduced dosing and infusion rates (as a result of tubular toxicity in kidney injury) is also indicated. An alternative to bisphosphonates is denosumab, which is not nephrotoxic. The use of furosemide may worsen cast formation and induce volume depletion; it should be used with caution or avoided.
• The second key strategy is the early use of chemotherapy (see Question 12) to reduce the LC load. In all patients, dexamethasone, 20 mg bid, which induces apoptosis of plasma cells, can be immediately commenced to rapidly lower the serum LC load.
