Which of the following is the commonest cause of salt wasting nephropathy?

NSAIDS can cause tubal interstitial disease and hence impair the urine concentrating ability of the kidney. Patients with analgesic nephropathy have predominantly tubulomedullary dysfunction characterized by impaired concentrating ability, acidification defects and occasionally a salt-losing state. Proteinuria tends to be low to moderate in quantity which is typically a mixture of glomerular and tubular in origin.