An object of the present invention is to provide an agent for preventing or ameliorating renal dysfunction, excellent in the inhibitory action on the advance of renal dysfunction, the suppressive action on renal fibrosis, the suppressive action on the development of renal failure, and the suppressive action on nephritis. The administration of an agent for preventing or ameliorating renal dysfunction, containing lubiprostone or its pharmacologically acceptable salt as an active ingredient by a method, such as oral administration, can inhibit the advance of renal dysfunction, suppress renal fibrosis, suppress the development of renal failure, and suppress nephritis, and thus can prevent or ameliorate nephritides, such as acute glomerulonephritis, minimal change nephritis, chronic glomerulonephritis, renal sclerosis, membrane proliferative nephritis, mesangial proliferative glomerulonephritis, membrane proliferative glomerulonephritis, crescentic nephritis, rapidly progressive glomerulonephritis, membranous glomerulonephritis, tubulointerstitial nephritis, acute pyelonephritis, chronic pyelonephritis, endocapillary proliferative nephritis, and lupus nephritis； renal failures, such as acute renal failure and chronic renal failure； and renal dysfunctions, such as amyloid kidney, membranous nephropathy, focal glomerulosclerosis, IgA nephropathy, acute tubular necrosis, nephrotic syndrome, diabetic nephropathy, gouty kidney, renal edema, renal tumors, renal ischemic disorders, and renal ischemia-reperfusion injury.
