Proteinuria: diagnostic approach — formative SAQs

Question 1 (12 marks)

A 14-year-old girl is found to have 1+ protein on a dipstick at a school sports screen. She is asymptomatic, her blood pressure is at the 50th centile for age, sex and height, and she is otherwise well. [6]

a) State the first investigation you would perform and the reason it is done before any further testing. (3 marks) [2]

b) Her daytime dipsticks remain 1+ to 2+ over the next two weeks, but a first-morning void passed immediately on waking has a UPr/Cr of 0.1 mg/mg. Name the diagnosis and outline the management and follow-up. (5 marks) [4]

c) Explain two ways in which the modern understanding of this diagnosis differs from the traditional teaching, and state the implication for follow-up. (4 marks) [5]

Question 2 (8 marks)

A 6-year-old boy presents with periorbital oedema. His blood pressure is at the 60th centile, his serum albumin is 17 g/L, and a spot first-morning UPr/Cr is 4.8 mg/mg. [2]

a) Define nephrotic-range proteinuria using two accepted thresholds and state whether this child meets it. (3 marks) [1]

b) Outline the immediate management priorities while the nephrology workup proceeds. (3 marks) [10]

c) Give two clinical features that, if present instead, would indicate urgent nephrology referral for suspected glomerulonephritis rather than straightforward nephrotic syndrome. (2 marks) [2]

Model answer notes (for examiner use, not for candidates)

Q1a) Confirm the proteinuria on two to three repeat first-morning urine samples taken weeks apart when the child is well. The first-morning sample is the test because it is passed after overnight recumbency, so a normal value excludes orthostatic proteinuria, and resolution on repeat excludes transient (functional) proteinuria. Confirming before classifying prevents over-investigation of a physiological finding. [2]

Q1b) The diagnosis is orthostatic (postural) proteinuria: the normal first-morning (recumbent) UPr/Cr with elevated daytime proteinuria is the defining feature. Management is reassurance of the family with long-term periodic monitoring of blood pressure, urinalysis and renal function, because the pattern is benign in the great majority but not universally so. [4]

Q1c) First, recent long-term follow-up data show that a minority of patients with orthostatic proteinuria develop sustained proteinuria, hypertension or renal functional change over decades, tempering the traditional view that the condition is uniformly benign. Second, the modern stance is reassurance with monitoring rather than reassurance with discharge. The implication is that the child needs periodic follow-up and re-evaluation of any change in pattern, blood pressure or function, with nephrology referral if these change. [5]

Q2a) Nephrotic-range proteinuria is a UPr/Cr over 2 mg/mg, corresponding to a urinary protein excretion over 1000 mg per square metre per day or over 40 mg per square metre per hour. This child's UPr/Cr of 4.8 mg/mg with an albumin of 17 g/L meets nephrotic-range proteinuria, and with the oedema and hypoalbuminaemia he has nephrotic syndrome. [1]

Q2b) Assess volume status (looking for hypovolaemia from the shift of fluid out of the vascular space), screen for and treat precipitating infection because spontaneous bacterial peritonitis is a recognised risk, assess thrombotic risk, and refer urgently for the nephrotic-syndrome workup and the renal biopsy decision. [10]

Q2c) Persistent proteinuria with macroscopic haematuria and red-cell casts, or proteinuria with a blood pressure at or above the 95th centile, would indicate a glomerulonephritis and urgent nephrology referral rather than straightforward steroid-responsive nephrotic syndrome. [2]