Chronic kidney disease

Overview

•CKD = kidney damage or reduced GFR persisting >3 months

•Paediatric CKD is predominantly structural in origin - unlike adult CKD (diabetes/hypertension)

•Prevalence ~50-75 per million children in the UK; boys affected more than girls

Causes

•CAKUT (congenital anomalies of the kidney and urinary tract) - ~40-50%; renal hypoplasia/dysplasia, posterior urethral valves, vesicoureteric reflux/reflux nephropathy; often detected antenatally

•Glomerulonephritis - FSGS, IgA nephropathy, lupus nephritis

•Hereditary nephropathies - Alport syndrome, polycystic kidney disease

Classification

•Staged by GFR category (G1-G5) and albuminuria category (A1-A3)

•GFR estimated using the Schwartz equation (uses height + serum creatinine) in children

•Normal GFR rises from ~20-30 mL/min/1.73m² at birth to ~90-120 mL/min/1.73m² in early childhood - staging must be age-adjusted

•Albuminuria: A1 = ACR <3 mg/mmol | A2 = ACR 3-30 mg/mmol | A3 = ACR >30 mg/mmol

⚠️

Serum creatinine remains within normal range until approximately 50% of renal function is lost - do not rely on it alone to exclude CKD.

Presentation

•Early CKD (G1-G2) is frequently asymptomatic - often found incidentally

•Growth failure - key paediatric feature; metabolic acidosis + GH resistance

•Hypertension - up to 50%; sodium/water retention + RAAS activation; may be the presenting finding

•Pallor and fatigue - normochromic normocytic anaemia (reduced EPO)

•Polyuria and polydipsia - impaired concentrating ability; important paediatric clue

•Oedema - nephrotic-range proteinuria or fluid overload in later stages

•Bone pain / rickets - renal osteodystrophy (reduced vitamin D activation + secondary hyperparathyroidism)

•Uraemic symptoms (anorexia, nausea, lethargy) - G4-G5

🎯

Growth failure + hypertension in a child should always prompt assessment of renal function.

Investigations

🥇 First-line

•serum creatinine + eGFR (Schwartz equation)

•urine ACR (early morning first-void) - quantifies proteinuria, defines albuminuria category

•renal ultrasound - identifies structural cause; small echogenic kidneys suggest chronicity

•electrolytes + bicarbonate - hyperkalaemia, metabolic acidosis (↓HCO3-), ↑urea in advanced CKD

•FBC - normochromic normocytic anaemia

•calcium, phosphate, PTH, 25-hydroxyvitamin D, alkaline phosphatase - assess CKD-MBD

•urine dipstick and microscopy - haematuria/proteinuria suggest glomerulonephritis; casts are highly informative

🥈 Second-line

•DMSA scintigraphy - differential renal function and cortical scarring (reflux nephropathy)

•MAG3 renogram - obstruction/drainage assessment

•immunology (ANA, ANCA, complement, anti-GBM) - if glomerulonephritis suspected

🏆 Gold standard

•renal biopsy - histological diagnosis where tissue result will change management

Management

•Best delivered through specialist paediatric nephrology MDT (nephrologist, dietitian, specialist nurse, psychologist)

•Blood pressure control - target <50th centile for age/height/sex; ACE inhibitors (e.g. enalapril) or ARBs first-line - reduce glomerular hypertension and proteinuria via RAAS blockade

•Metabolic acidosis - oral sodium bicarbonate to maintain serum bicarbonate ≥22 mmol/L; acidosis drives protein catabolism and worsens growth

•Anaemia - optimise iron stores first (oral/IV iron); if iron-replete anaemia persists, add ESA (darbepoetin alfa)

•CKD-MBD - restrict dietary phosphate; calcium carbonate (calcium-based phosphate binder) with meals; if hypercalcaemia develops, switch to/add sevelamer carbonate (non-calcium-based)

•Vitamin D - alfacalcidol (active 1-alpha vitamin D) - standard vitamin D cannot be hydroxylated by the failing kidney

•Growth failure - correct acidosis and malnutrition first; recombinant human growth hormone (rhGH) in G2-G5 with height below -2 SD after nutritional/metabolic optimisation

•Treat underlying cause - surgical correction of obstructive uropathy, immunosuppression for glomerulonephritis

•Renal replacement therapy (RRT) - G5 or uncontrollable uraemia/fluid overload/electrolyte disturbance; peritoneal dialysis preferred in younger children (home-based); renal transplantation is the optimal long-term option

🚨

Sick day rules: during intercurrent illness (vomiting/diarrhoea/reduced intake), temporarily withhold NSAIDs, ACE inhibitors, and ARBs to prevent acute-on-chronic kidney injury. Parents must be educated on this.

Complications

Key complications of CKD in children

Complication	Mechanism	Key management
Anaemia	↓ EPO → normochromic normocytic anaemia	Iron then ESA (darbepoetin alfa)
CKD-MBD / rickets	Phosphate retention → ↓ active vitamin D → secondary hyperparathyroidism → bone resorption	Phosphate restriction, binders, alfacalcidol
Hypertension	Na/water retention + RAAS overactivation → LVH if untreated	ACE inhibitor / ARB
Metabolic acidosis	↓ acid excretion + ↓ HCO3- regeneration; worsens growth and bone disease	Sodium bicarbonate (target HCO3- ≥22 mmol/L)
Growth failure	Acidosis, malnutrition, anaemia, osteodystrophy, GH/IGF-1 resistance	Correct metabolic derangements; rhGH if height <-2 SD
Hyperkalaemia	Impaired K+ excretion; worsened by ACE inhibitors and high dietary K+	Dietary restriction; adjust medications
Cardiovascular disease	Leading cause of mortality; hypertension, dyslipidaemia, anaemia, hyperphosphataemia	BP control, treat all contributing factors

Prognosis

•Cardiovascular disease is the leading cause of mortality even in children with CKD

•CAKUT with preserved renal mass - may be stable for years; glomerulonephritis/hereditary nephropathies often progress to G5 in adolescence

•Renal transplantation offers best long-term survival and quality of life; pre-emptive transplantation (before dialysis) associated with superior graft function

•Post-AKI: monitor for at least 3 years even if eGFR returns to baseline (longer for stage 3 AKI) as CKD can develop silently