Haematuria: diagnostic approach — branching viva

Opening — framing the problem

The examiner begins: a 7-year-old boy passes cola-coloured urine, has peri-orbital swelling and a blood pressure at the ninety-fifth centile, two weeks after a sore throat. What is your first framework for thinking about this? [8]

My first framework is the glomerular versus non-glomerular split, read from the colour of the urine and the cells it carries. Cola-coloured urine with red-cell casts, dysmorphic red cells and proteinuria points to a glomerular source, and the one to three week latency after a streptococcal throat infection points specifically to post-streptococcal glomerulonephritis. Before any blood test I confirm he is not in a hypertensive emergency, because his blood pressure is already at the limit and a nephritic child can deteriorate quickly. [8] [1]

Branch A — the complement pattern

What complement and serology pattern do you expect, and how does it differ from IgA nephropathy? [8]

In post-streptococcal glomerulonephritis the immune-complex deposition activates the alternative pathway, so C3 is low while C4 is typically normal, and the anti-streptolysin O and anti-DNase B titres are raised. The C3 usually normalises within six to eight weeks. IgA nephropathy differs in both timing and complement: it gives synpharyngitic cola urine appearing at the same time as the sore throat, and its complement is characteristically normal. [8] [6]

Branch B — the dipstick that lies

Now a different child: the dipstick is strongly positive for blood but the microscopy shows no red cells, and the child is lethargic with aching muscles. What is going on, and what do you do? [1]

A positive dipstick with no red cells is not haematuria. The dipstick detects haem peroxidase activity, so it is positive for intact red cells, free haemoglobin and myoglobin alike. With no red cells on microscopy and aching muscles after a viral illness, I exclude myoglobinuria from rhabdomyolysis and haemoglobinuria from haemolysis, sending a creatine kinase and a haemolysis screen. Both can be rapidly dangerous, so I confirm the absence of true haematuria before I label the urine. [1]

Branch C — the mass that must not be biopsied

Finally, a 2-year-old has painless visible haematuria and the parent has noticed a large abdominal mass. How does your management change? [3]

A painless abdominal mass with haematuria in a young child may be a Wilms tumour, and percutaneous biopsy risks tumour spillage and upstaging of the disease. I obtain imaging first and involve the oncology or surgical team before any tissue is taken. The rule I hold is that any unexplained renal mass in a child is imaged and referred before it is biopsied. [3]

Closing — the safety rule

Give me the single rule you want every junior to hold about haematuria in children. [1]

Confirm that the red or brown urine really is blood with microscopy showing more than five red cells per high-power field, then split it into a glomerular and a non-glomerular source, because that single fork decides the whole investigation pathway. Measure the blood pressure in every child, and escalate for the red flags of hypertension, oedema, oliguria, significant proteinuria and an abdominal mass. [1] [8]