Fatemeh Akbarian, MD, Research Fellow, University of Toronto, Toronto, ON.
Hatim Al Lawati, MD, FRCPC, Cardiology Resident, Division of Cardiology, Faculty of Medicine, University of Toronto, Toronto, ON.
Mohammad Ali Shafiee, MD, FRCPC, General Internist, Nephrologist, Department of Medicine, Toronto General Hospital, University Health Network; Clinician Teacher, University of Toronto, Toronto, ON.

Abstract
Proteinuria can create one of the greatest challenges in primary practice, especially in the geriatric population. It is typically detected by dipstick urinalysis, an ordinary, non-invasive test. Proteinuria is frequently a marker of unsuspected kidney disease, progressive atherosclerosis or a systemic disease. There is a strong correlation between urinary protein excretion and progression of renal failure. Furthermore, Proteinuria is a strong and independent predictor of increased risk for cardiovascular disease and death, especially in people with diabetes, hypertension, chronic kidney disease, and the elderly. This article will review the clinical significance of proteinuria in adults, especially in the elderly population, and provide a practical diagnostic approach in addition to a summary of non-specific antiproteinuric therapy.
Keywords: Proteinuria, Microalbuminuria, Macroalbuminuria, elderly, Risk Factor.

D'Arcy Little, MD, CCFP
Director of Medical Education,
York Community Services, Toronto, ON

Introduction
Proteinuria, defined as the presence of urinary protein in concentrations greater than 0.3 g/d on a 24-hour collection, or greater than 1+ protein on a dipstick, is a common finding, which occurs in approximately 10% of elderly patients.¹ Although proteinuria has been regarded as "the first sign of serious renal disease",² its presence can represent anything from a benign abnormality to the signpost of significant disease,¹ with the potential for progressive renal insufficiency.³ Because of the variable significance and multiple causes of proteinuria, the clinician requires a systematic approach for the work-up of this condition in the older patient. This paper will review the renal physiology associated with proteinuria, the classification of proteinuria, and an approach to the diagnosis of proteinuria in the older patient.

Renal Physiology
Approximately 15 kilograms of protein passes through the adult kidney in a single day.³ However, in a healthy adult, only up to 150 mg of protein should be excreted per day, for protein excretion levels to be considered normal.