<prompt> The commonest cause of chronic renal failure is-Diabetes mellitusHypeensionPyelonephritisCystic disease of kidneys  <response>: The most common cause of chronic renal failure is diabetes mellitus 20-40- high blood sugar levels caused by diabetes damage blood vessels in the kidneys diabetic nephropathy. Hypeension5-20 - damages blood vessels, cystic diseases of the kidney5, recurrent pyelonephritis, glomerular and tubulo-interstitial diseases, drugs etc. are other common causes of CKD. Reference : page 484 Davidsons Principles and practice of Medicine 22nd edition 