Abstract: A method for determining whether a urine sample has been obtained from a subject suffering from a kidney disorder involving kidney damage. The method is based on determining the level of a proteolytic enzyme in urine from the subject. Sample and optionally comparing this level with a reference value. The proteolytic enzyme preferably is a matrix metalloproteases, in particular MMP-2 or MMP-9. The method is particularly suitable for subjects with a condition or disorder that is associated with an increased risk of kidney disorders, such as diabetes. The method may adavnatageously be applied for early detection of kidney damage, in particular when the subject does not yet show any sign of microalbuminuria. The method may also be applied to a subject undergoing dialysis for determining whether the subject is suffering from remodelling of the peritoneal membrane. Thus, the method is particularly suited for patients undergoing continuous ambulatory peritoneal dialysis.