The investigation of proteinuria

Summary 

Proteinuria can be a major clue to underlying renal disease or a transient finding in normal children. This article will deal with the evaluation of a child with proteinuria, what basic investigations are needed and when to refer to a paediatric nephrologist.

Urinalysis sticks for ward testing are quite sensitive for proteinuria. Suspected proteinuria should always be sent for laboratory quantification, and the simplest method is to measure with the protein:creatinine ratio on a spot sample.

Physiological proteinuria is not usually detected on urinalysis or dipstick testing. Causes of non-physiological proteinuria include benign transient proteinuria, orthostatic, renal and non-renal causes. Persistent proteinuria is more significant. It is also likely to be more significant if associated with haematuria or hypertension. Orthostatic proteinuria can only be diagnosed when the urinary protein from a recumbent sample reduces to normal.

When there is persistent non-orthostatic proteinuria, baseline investigations would normally include a renal ultrasound and a plasma chemistry profile. Plasma albumin gives a good indication of the significance of proteinuria. If haematuria is also present, a basic nephritis screen should also be carried out. Any child with persistent non-orthostatic proteinuria should be referred to a paediatric nephrologist for consideration for renal biopsy.

Keywords: Proteinuria, Orthostatic proteinuria, Nephrotic syndrome, Glomerulonephritis, Chronic renal failure/chronic kidney disease, Urinalysis