Assessment and triage of paediatric haematuria in primary care: A practical guide for GP registrars

Differential diagnosis: glomerular vs. non-glomerular

The fundamental step in assessing haematuria is determining its source: glomerular (from the kidney parenchyma/glomerulus) or non-glomerular (from the collecting system or lower urinary tract). Glomerular causes involve damage to the glomerular basement membrane. These are associated with systemic symptoms such as hypertension, oedema, and proteinuria. Examples include post-infectious glomerulonephritis (PIGN), which typically follows a streptococcal infection by 1–3 weeks, and immunogloblin A (IgA) nephropathy, which often presents with recurrent haematuria concurrent with a viral illness. Non-glomerular causes involve bleeding distal to the glomeruli. Hypercalciuria is a common cause of isolated, often recurrent, haematuria in children and is a key diagnosis to screen for in primary care (Srivastava and Schwaderer, 2009). Wilms’ tumour (nephroblastoma), the most common renal malignancy, presents primarily as an asymptomatic abdominal mass, though haematuria may occur in up to 25% of cases (Green, 1985). The initial assessment in general practice is essential for safe triage. Table 1 outlines aetiological classifications and key findings in haematuria.

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Table 1.

Aetiological classification and triage of paediatric haematuria.

Category	Typical urine finding	Key primary care examples	Triage implications
Transient/benign	Isomorphic RBCs, low/no protein	UTI, fever/viral illness, post-exercise	Safety-netting and observation
Glomerular	Dysmorphic RBCs, RBC casts, proteinuria, ‘cola-coloured’ urine	Post-infectious glomerulonephritis (PIGN), IgA nephropathy, Alport’s syndrome	Urgent nephrology referral
Non-glomerular	Isomorphic RBCs, usually no protein	Hypercalciuria/renal calculi, structural abnormalities, Wilms’ tumour (abdominal mass)	Urology workup or urgent paediatric referral (mass)

History

A focused history is crucial to guide investigation, starting with the colour of the urine: smoky, brown, or cola-coloured urine is highly suggestive of glomerular bleeding due to oxidised red blood cells and is therefore a high-suspicion finding for nephritis, whereas bright red urine or the presence of clots points more towards lower urinary tract (urological) bleeding. Recent illness is also important, as an upper respiratory or skin infection in the preceding 1–3 weeks is highly relevant for post-infectious glomerulonephritis due to its delayed onset, while haematuria occurring simultaneously with a viral illness is more suggestive of IgA nephropathy. Associated symptoms should be explored, including dysuria or loin pain, which may indicate urinary tract infection or renal stones, as well as oedema (periorbital or dependent) or foamy urine, which suggests significant proteinuria or a nephrotic component. Finally, a family history of deafness and renal disease should raise suspicion for Alport’s syndrome.

Physical examination

The physical examination must focus on vital signs and evidence of systemic illness, with particular attention to blood pressure, which must be measured accurately using an appropriately sized cuff and interpreted against age- and height-adjusted paediatric centile charts; readings at or above the 95th centile indicate hypertension and represent a major red flag requiring urgent referral, with the National Institutes of Health’s paediatric blood pressure charts serving as useful reference tools (National High Blood Pressure Education Program Working Group on High Blood Pressure in Children and Adolescents, 2004). The examination should also assess for oedema, particularly periorbital or dependent oedema, which indicates fluid retention and possible renal compromise. Abdominal palpation is essential to assess for a renal or abdominal mass; however, if a mass is detected, palpation should not be forceful due to the risk of capsular rupture, and this finding mandates immediate urgent referral to paediatric services or paediatric nephrology care.

Urine dipstick and microscopy

A positive urine dipstick for blood indicates the presence of haemoglobin or myoglobin and must be confirmed with formal urine microscopy to exclude pseudo-haematuria, such as urine discolouration from food, medications, or myoglobinuria secondary to rhabdomyolysis. Urine microscopy is the most valuable step in the primary care assessment because it helps distinguish glomerular from non-glomerular haematuria. The presence of dysmorphic red blood cells – particularly acanthocytes – reflects red cells that have traversed a damaged glomerular basement membrane and is highly specific for glomerular haematuria, warranting urgent referral to paediatric nephrology (Kohler et al, 1991). Red blood cell casts represent aggregates of erythrocytes within a protein matrix and are pathognomonic of acute glomerulonephritis, requiring immediate specialist referral. In contrast, isomorphic (uniformly shaped) red blood cells suggest a non-glomerular source of bleeding from the lower urinary tract and should prompt further urological evaluation, including screening for hypercalciuria. The presence of co-existing significant proteinuria, defined as a protein-to-creatinine ratio greater than 20 mg/mmol, alongside haematuria is a concerning feature and strengthens the indication for specialist referral (Gauci et al., 2023).

Initial blood and urine tests

If red flags (e.g. hypertension, oedema, dysmorphic RBCs, oliguria) are present, urgent referral should take priority, and investigations should not delay transfer to secondary care. Where clinically appropriate and where this does not delay referral, the investigations oulined below may be considered in primary care or requested by paediatrics on admission.

Baseline renal function should be assessed with urea, creatinine and electrolytes (U&Es) to evaluate for acute kidney injury. Where glomerulonephritis is suspected, a targeted immunological screen should be performed, including an antistreptolysin O (ASO) titre or streptozyme test to identify recent streptococcal infection consistent with post-infectious glomerulonephritis, along with complement levels (C3 and C4), because transiently low C3 levels are characteristic of this condition (Horvath et al., 2022). In cases where a non-glomerular source is suspected, screening for hypercalciuria is recommended, with a random urinary calcium-to-creatinine ratio greater than 0.6 suggesting hypercalciuria.

Management and rationale

Case scenario 2 presents a picture of recurrent UTI and non-glomerular haematuria, where the primary concern is underlying urological pathology or metabolic cause, rather than acute nephritis. Recurrent UTIs in a young child (under 2 years), particularly a girl, are a concern for underlying structural or functional abnormalities (e.g. vesicoureteral reflux or obstructive uropathy). The haematuria is intermittent and the red cells are isomorphic, suggesting a non-glomerular (urological) source. The absence of systemic red flags (normal blood pressure, no oedema, no proteinuria) makes acute nephritis unlikely.

Because acute red flags are absent, urgent referral is not required, but the history of recurrent UTIs warrants a systematic investigation for non-glomerular causes and underlying structural issues.

Case 2 demonstrates the need to investigate underlying structural or metabolic causes in children with recurrent symptoms and non-glomerular haematuria.