Proteinuria: diagnostic approach — case

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A 14-year-old girl is found to have 1+ protein on a dipstick at a school sports screen. She is asymptomatic, trains as a long-distance runner, and has no oedema, haematuria or family history of renal disease. Her blood pressure is at the 50th centile for age, sex and height. [6]

Task 1 — Confirmation (5 minutes)

State the first step in the workup. Confirm the proteinuria on two to three repeat first-morning urine samples taken weeks apart when she is well, because a single dipstick reading during exercise is most likely transient (functional) proteinuria. Explain that the first-morning void is the test because it is passed after overnight recumbency, so a normal first-morning ratio excludes orthostatic proteinuria. Measure her blood pressure on paediatric centiles and examine for oedema and growth failure before any further testing. [2]

Task 2 — Quantification and classification (5 minutes)

Interpret the repeat findings: her daytime dipsticks remain 1+ to 2+ over two weeks, but a first-morning void passed immediately on waking has a UPr/Cr of 0.1 mg/mg. Classify this as orthostatic (postural) proteinuria, defined by the normal first-morning (recumbent) UPr/Cr with elevated daytime excretion. State the normal threshold: a first-morning UPr/Cr under 0.2 mg/mg in the child over two years. Distinguish this from persistent pathological proteinuria, which is present on every sample including the first-morning void, and from nephrotic-range proteinuria, which is a UPr/Cr over 2 mg/mg. [1]

Task 3 — Prognosis and follow-up (5 minutes)

Counsel the family on the prognosis and the follow-up plan. State that the traditional teaching held orthostatic proteinuria to be uniformly benign, but that recent long-term data show a minority of affected individuals develop sustained proteinuria, hypertension or renal functional change over decades. Arrange periodic monitoring of blood pressure, urinalysis and renal function, lengthening the interval if the values stay normal, and refer to nephrology if the pattern, the blood pressure or the function changes. State explicitly that reassurance is paired with monitoring, not with discharge. [4] [5]

Task 4 — Safety-netting and red flags (5 minutes)

Give the family a clear safety-net. Tell them to return urgently if the child develops periorbital or leg oedema, macroscopic (cola-coloured) haematuria, a severe headache or visual symptoms suggesting hypertension, or a reduced urine output. Explain that these features would signal a change from the benign orthostatic pattern to a significant renal disease such as nephrotic syndrome or glomerulonephritis, and that the monitoring plan exists to catch such a change early. [6]