The invention provides methods and kits for diagnosing a renal disease in a patient or for predicting the risk of a patient for developing a renal disease. In one embodiment, the invention provides a method for diagnosing a renal disease in a patient, comprising determining the level of a ubiquitin fragment having a mass-to-charge ratio (m/z) of 6188 (ubiquitin m/z 6188), or the level of a nucleic acid encoding ubiquitin m/z 6188, in a sample derived from said patient, wherein the substantial absence or a reduced level of less than 25% of ubiquitin m/z 6188 or the nucleic acid encoding ubiquitin m/z 6188 compared to a control is indicative of the renal disease in said patient.