Wilms tumour (nephroblastoma) is the most important malignant cause of haematuria in children — it is the most common renal tumour in childhood, occurring predominantly between ages 3-4 years (range 1-8 years). The classic presentation is an abdominal mass discovered incidentally by a parent or during examination, often with haematuria. The cardinal rule: do not repeatedly palpate the abdomen if Wilms tumour is suspected — the tumour has a fibrous capsule that can rupture with vigorous palpation, causing intraperitoneal bleeding and tumour dissemination. After a single careful examination that identifies an abdominal mass, consider very urgent referral (appointment within 48 hours, NICE NG12) without further abdominal palpation and document the finding. Prognosis for Wilms tumour is generally good with modern treatment (surgery + chemotherapy ± radiotherapy for high-stage disease). Early identification is the key GP contribution.

The acanthocyte test is the most specific microscopic finding for glomerular haematuria — acanthocytes are red blood cells with irregular membrane protrusions ('blebs' or 'spicules') that form as the cells are squeezed through damaged glomerular basement membrane. They are best seen on phase-contrast microscopy; on standard light microscopy they appear as ring-shaped or crenated cells. A high proportion of acanthocytes is specific, but not sensitive, for glomerular disease. The presence of RBC casts is even more specific — these are red cells embedded in a Tamm-Horsfall protein matrix that forms in the renal tubules, confirming that the bleeding is intra-glomerular. Dipstick haematuria with visible acanthocytes or RBC casts on urine microscopy is a strong indication for urgent nephrology referral. GPs can request urine microscopy when glomerular haematuria is suspected, where available — but this must not delay referral of obvious nephritic features.

The urine protein:creatinine ratio (uPCR) is the most clinically useful quantification of proteinuria in children — it correlates well with 24-hour urine protein excretion and is far more practical than a timed urine collection. Interpret uPCR using age-specific laboratory ranges and the local paediatric nephrology pathway: above approximately 20 mg/mmol is abnormal in many paediatric pathways; above 100 mg/mmol is significant and should prompt urgent clinical assessment, particularly with haematuria, hypertension or impaired renal function, but is not "nephrotic range"; nephrotic-range proteinuria is generally around 200 mg/mmol or more, or per the local definition. Do not use uPCR alone to determine urgency — check BP, creatinine/eGFR, serum albumin, fluid status and urine microscopy. Significant proteinuria with haematuria, hypertension, oedema or reduced renal function warrants urgent paediatric/nephrology advice. Isolated haematuria (without proteinuria, hypertension, or renal impairment) has a much broader differential and more benign prognosis — thin basement membrane disease, IgA nephropathy (mild), exercise-induced, or benign familial haematuria. The combination of haematuria + proteinuria is the most important investigation result in paediatric haematuria assessment.

Hypercalciuria is the most common cause of persistent isolated microscopic haematuria in children in the absence of proteinuria or renal impairment — it is a recognised finding in children with isolated microscopic haematuria when properly investigated. The mechanism: excess urinary calcium crystallises in the tubules and collecting system, causing microtrauma to the urothelium and red cell leak. The diagnosis: spot urine calcium:creatinine ratio interpreted by age-specific reference ranges. Confirmed hypercalciuria with no other cause of haematuria: do not restrict dietary calcium (risks bone density effects); reduce excess dietary sodium; normal age-appropriate fluids; thiazide diuretics only if directed by paediatric nephrology for recurrent calcium stones or symptomatic hypercalciuria. Paediatric nephrology referral for stone-forming hypercalciuria or persistent unexplained haematuria.

The isolated asymptomatic microscopic haematuria management pathway in children is defined by the British Association of Paediatric Nephrology (BAPN) guidance — it requires structured investigation and long-term follow-up rather than immediate nephrology referral. Confirm persistence on repeat urine samples (to exclude transient causes — exercise, menstruation, minor UTI) using the local definition; if persistent, check uPCR and BP ± renal function, reserving ultrasound for specific indications; if all are normal, regular GP review per the local paediatric nephrology pathway is usually sufficient. The key safety-net: escalate to paediatric nephrology if at any annual review the child develops proteinuria (uPCR rising above 20 mg/mmol), hypertension, or renal impairment — these features suggest glomerular disease and need paediatric nephrology assessment.

IgA nephropathy (Berger's disease) management in children is based largely on adult data (KDIGO 2021): ACE inhibitors/ARBs (ramipril or losartan) are the cornerstone of treatment for IgA nephropathy with proteinuria, providing both antiproteinuric and nephroprotective effects independent of blood pressure reduction. In usual paediatric nephrology practice an ACE inhibitor is started for children with IgA nephropathy and persistent significant proteinuria (threshold set by the specialist team). Corticosteroid use in IgA nephropathy is based largely on adult trial data and is a specialist decision. For children with significant IgA nephropathy, ACE inhibitor ± corticosteroid treatment is initiated and monitored by paediatric nephrology — not by the GP.

The testicular involvement in HSP deserves explicit mention because testicular torsion can complicate HSP and presents a surgical emergency — the vasculitis of HSP can affect the small vessels of the testes, causing scrotal pain and swelling that can be confused with epididymo-orchitis. However, HSP-associated scrotal pain may also indicate true testicular torsion (which occurs at the same age group as HSP — school-age boys). Any HSP patient presenting with scrotal pain must have testicular torsion excluded urgently — an immediate surgical opinion (salvage of a torted testis is time-critical; ultrasound must not delay referral). A 'wait and see' approach to scrotal pain in any male of any age is never acceptable if torsion cannot be excluded clinically.

Registry data (European Alport Registry, Gross et al, Kidney International 2012) suggest that earlier ACE inhibitor therapy delays kidney failure in Alport syndrome — but initiation, timing and dosing are directed by paediatric nephrology according to genotype, proteinuria, renal function and BP. The mechanism: GFR loss in Alport syndrome is driven by glomerular hypertension from the abnormal GBM, and ACE inhibitor-mediated reduction in intraglomerular pressure provides nephroprotection. GPs who identify persistent microscopic haematuria in a boy with a family history of hearing loss, haematuria, or renal failure should have a very low threshold for referral to paediatric nephrology — early specialist diagnosis allows timely treatment decisions.

The annual follow-up of isolated asymptomatic microscopic haematuria in children is a long-term commitment that requires proactive recall and documentation — many children with 'benign' isolated haematuria (thin basement membrane disease, mild IgA nephropathy, hypercalciuria) will never develop clinical problems, but a minority will develop proteinuria, hypertension, or renal impairment over the following years. The GP's role is to maintain a safety net: a child who was labelled 'isolated microscopic haematuria — benign' at age 8 and never reviewed again, who presents at age 22 with stage 3 CKD, represents a missed opportunity for specialist nephroprotective treatment. The recall system should be integrated into the practice's chronic disease register or coded appropriately (SNOMED CT haematuria code) to ensure the annual check is flagged. If the GP practice does not have a recall system for paediatric haematuria, the referral letter to community paediatrics should specify the monitoring requirements.