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Assessment of urinary protein excretion and evaluation of isolated non-nephrotic proteinuria in adults

Author
Brad H Rovin, MD
Section Editors
Richard J Glassock, MD, MACP
Gary C Curhan, MD, ScD
Deputy Editor
Albert Q Lam, MD

INTRODUCTION

Total urinary protein excretion in the normal adult should be less than 150 mg/day. Higher rates of protein excretion that persist beyond a single measurement should be evaluated, as they often imply an increase in glomerular permeability that allows the filtration of normally non-filtered macromolecules, such as albumin.

The assessment of urinary protein excretion and the evaluation of isolated non-nephrotic proteinuria in adults will be reviewed here. The approach to adults with nephrotic-range proteinuria or hematuria and the evaluation of children with proteinuria are presented elsewhere. (See "Overview of heavy proteinuria and the nephrotic syndrome" and "Etiology and evaluation of hematuria in adults" and "Differential diagnosis and evaluation of glomerular disease" and "Evaluation of proteinuria in children".)

Issues related to moderately increased albuminuria (formerly called "microalbuminuria"), which is different from non-nephrotic proteinuria, are discussed separately. (See "Moderately increased albuminuria (microalbuminuria) in type 1 diabetes mellitus" and "Moderately increased albuminuria (microalbuminuria) in type 2 diabetes mellitus" and "Moderately increased albuminuria (microalbuminuria) and cardiovascular disease".)

DEFINITIONS

Isolated proteinuria — Isolated proteinuria is defined as proteinuria without abnormalities in the urinary sediment, including hematuria, or a reduction in glomerular filtration rate (GFR), as well as the absence of hypertension or diabetes. In most cases of isolated proteinuria, the patient is asymptomatic, and the presence of proteinuria is discovered incidentally by use of a dipstick during routine urinalysis. The urine sediment is unremarkable (fewer than three erythrocytes per high-power field and no casts), protein excretion is less than 3.5 g/day (non-nephrotic), serologic markers of systemic disease are absent, and there is no hypertension, diabetes, and also no edema or hypoalbuminemia.

This benign presentation of isolated non-nephrotic proteinuria is different from that in patients with more prominent renal disease who have one or more of the following: nephrotic-range proteinuria (≥3.5 g/day), lipiduria, edema, hypoalbuminemia, and/or an active urine sediment containing red cells (which are often dysmorphic) and red cell casts.

                             

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Literature review current through: Nov 2016. | This topic last updated: Fri Oct 07 00:00:00 GMT+00:00 2016.
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