PRoteinuria: How to interpret its meaning

Abstract

Introduction: Proteinuria is a common laboratorial finding in asymptomatic adults, which cannot be discounted in any circumstance. Dipstick urinalysis is by far the most used method for the detection of proteinuria, but because it has a high degree of false positive results, one should use other methods in its confirmation/follow up. Objectives: To perform a revision of the physiopathologic basis of proteinuria and of the methods currently used in its detection and quantification. To discuss its clinical importance and to present a possible diagnostic algorithm. To review the specific therapies, mainly in the context of Chronic Kidney Disease (CKD). Methods: We searched Pubmed for original articles, reviews and meta-analysis until April 2007. We also considered reference textbooks in Nephrology and Internal Medicine. Overall 63 articles were included. Conclusions: An algorithmic approach helps in distinguishing between benign causes (febrile disease, physical exercise, dehydration ) from other rarer, but more serious ones (glomerulopathies, monoclonal gammopathies). The detection of proteinuria in routine examinations must be confirmed, and in case of persistence, must be followed by a quantitative measurement (24-hour urine specimen or protein-to-creatinine ratio on a random urine specimen). Patients with persistent proteinuria, in whom the underlying etiology remains unclear after a thorough medical investigation, should be referred to a Nephrology consultation. In patients with CKD, early detection and treatment of asymptomatic proteinuria improves short and long-term prognosis. Considering the increasing prevalence of CKD in the general population, the General Practitioner plays an important role in identification of individuals at risk and in monitoring the associated risk factors, namely proteinuria.