48  Spectrum of Kidney Diseases in Children

48.1 Introduction

The kidneys play a vital role in maintaining internal homeostasis through the regulation of water, electrolytes, acid-base balance, and the excretion of metabolic waste. In children, renal function is essential not only for maintaining physiologic stability but also for supporting growth and development. Kidney diseases in children encompass a wide spectrum ranging from congenital and inherited disorders to acquired glomerular, tubular, and systemic conditions.

In Ghana and other low- and middle-income countries, kidney diseases in children are increasingly recognized as important causes of morbidity and mortality. Limited diagnostic facilities, late presentation, and inadequate access to nephrology services remain major challenges. Understanding the diverse presentation and underlying mechanisms of renal disease is, therefore, critical for early diagnosis and effective management.

48.2 Epidemiology and Burden

Globally, the prevalence of paediatric kidney disease varies widely depending on the specific condition. Acute kidney injury (AKI) is estimated to occur in up to 25% of hospitalized children, while chronic kidney disease (CKD) affects 1–3 per 1,000 children. In sub-Saharan Africa, data are scarce, but renal disease often presents late and is associated with preventable causes such as infections, dehydration, and toxins.

In Ghana, children frequently present with conditions such as nephrotic syndrome, acute glomerulonephritis, urinary tract infections, and congenital anomalies of the kidney and urinary tract (CAKUT). Early childhood illnesses, poor sanitation, and limited access to pediatric nephrology care contribute to adverse outcomes.

48.3 Classification of Kidney Diseases in Children

Kidney diseases in children can be broadly classified into the following categories:

1. Congenital and Structural Anomalies
   • Congenital anomalies of the kidney and urinary tract (CAKUT)
   • Obstructive uropathy (posterior urethral valves, ureteropelvic junction obstruction)
   • Renal dysplasia or hypoplasia
   • Polycystic kidney disease
2. Glomerular Diseases
   • Nephrotic syndrome (minimal change, focal segmental glomerulosclerosis, membranoproliferative)
   • Glomerulonephritis (post-streptococcal, IgA nephropathy, lupus nephritis)
   • Rapidly progressive glomerulonephritis
3. Tubulointerstitial and Tubular Disorders
   • Acute interstitial nephritis
   • Renal tubular acidosis
   • Fanconi syndrome
   • Cystinosis and other metabolic tubular disorders
4. Infective and Postinfectious Conditions
   • Urinary tract infection (UTI)
   • Pyelonephritis
   • Reflux nephropathy
   • Schistosomiasis-related kidney disease
5. Systemic and Secondary Causes
   • Hypertension
   • Diabetes mellitus (rare in children but increasing)
   • Sickle cell nephropathy
   • HIV-associated nephropathy
   • Hemolytic uremic syndrome (HUS)
6. Acute and Chronic Renal Failure
   • Acute kidney injury (AKI)
   • Chronic kidney disease (CKD) and end-stage renal disease (ESRD)

48.4 Pathophysiological Overview

The kidney’s response to injury varies depending on the site and nature of the insult.

48.4.1 Glomerular Diseases

These involve inflammation or damage to the glomeruli, leading to abnormal filtration.
- Nephrotic syndrome results from increased glomerular permeability to proteins, producing heavy proteinuria, hypoalbuminaemia, and oedema.
- Glomerulonephritis, on the other hand, causes hematuria, hypertension, and varying degrees of renal impairment. Immune-mediated mechanisms — such as deposition of immune complexes following infections — play a central role.

48.4.2 Tubulointerstitial and Tubular Disorders

Tubular diseases interfere with urine concentration, electrolyte handling, and acid-base balance.
- Renal tubular acidosis leads to metabolic acidosis due to defective hydrogen ion excretion or bicarbonate reabsorption.
- Fanconi syndrome affects multiple tubular transport mechanisms, leading to glycosuria, aminoaciduria, and phosphate wasting.

48.4.3 Vascular and Systemic Disorders

Conditions such as hemolytic uremic syndrome cause endothelial injury leading to microangiopathic hemolysis and acute renal failure. Hypertension, both a cause and consequence of renal disease, damages glomeruli and accelerates progression to chronic kidney disease.

48.4.4 Congenital and Structural Anomalies

CAKUT accounts for a significant proportion of pediatric renal failure. These abnormalities arise during embryogenesis and include renal agenesis, dysplasia, and obstructive lesions. Impaired nephron development or chronic obstruction eventually results in renal scarring and progressive dysfunction.

48.5 Clinical Presentation

Renal diseases in children present with diverse features depending on the site and extent of involvement.

Common presentations include: - Oedema, especially periorbital and pedal, typical of nephrotic syndrome.
- Haematuria (macroscopic or microscopic), often seen in glomerulonephritis.
- Hypertension, either as a primary finding or secondary to renal pathology.
- Oliguria or anuria, indicating renal failure.
- Polyuria and polydipsia, suggestive of tubular dysfunction.
- Recurrent urinary tract infections, possibly pointing to vesicoureteral reflux or obstruction.
- Growth retardation and failure to thrive, common in chronic kidney disease.

Infants may present with nonspecific signs such as poor feeding, vomiting, or failure to gain weight, necessitating a high index of suspicion.

48.6 Investigations

Diagnosis requires a combination of clinical assessment, laboratory tests, and imaging.

48.6.1 Laboratory Tests

• Urinalysis: detects proteinuria, hematuria, or pyuria.
  
• Urine microscopy and culture: identifies infection or casts.
  
• Serum urea and creatinine: assess renal function.
  
• Electrolytes and bicarbonate: for acid-base and electrolyte imbalances.
  
• Complement levels (C3, C4): decreased in post-streptococcal glomerulonephritis.
  
• Autoantibody testing: ANA, anti-dsDNA for lupus nephritis.
  
• 24-hour urine protein or spot protein-to-creatinine ratio to quantify proteinuria.

48.6.2 Imaging

• Renal ultrasound for kidney size, structure, and obstruction.
  
• Voiding cystourethrogram (VCUG) for reflux diagnosis.
  
• DMSA scan for renal scarring.
  
• CT/MRI in complex anomalies or masses.

48.6.3 Renal Biopsy

Indicated in cases of nephrotic syndrome unresponsive to steroids, unexplained renal failure, or to confirm a specific glomerular disease.

48.7 Management Principles

The management of pediatric kidney disease depends on the underlying cause but follows certain common principles.

48.7.1 1. General Supportive Care

• Control of blood pressure using ACE inhibitors or calcium channel blockers.
  
• Maintenance of fluid and electrolyte balance.
  
• Correction of metabolic acidosis and anemia.
  
• Adequate nutrition to support growth and prevent catabolism.

48.7.2 2. Disease-Specific Therapy

• Nephrotic syndrome: corticosteroids are first-line; resistant cases may need cyclophosphamide or calcineurin inhibitors.
  
• Acute glomerulonephritis: mainly supportive; antibiotics for streptococcal infection; control of hypertension and edema.
  
• UTIs: treated with appropriate antibiotics and preventive measures such as hydration and bladder hygiene.
  
• Obstructive uropathy: surgical intervention to relieve obstruction.
  
• AKI: manage underlying cause, ensure adequate perfusion, and initiate dialysis when necessary.
  
• CKD: slow progression through blood pressure control, treat anemia, and prepare for renal replacement therapy.

48.7.3 3. Dialysis and Renal Replacement

Indicated in severe AKI or end-stage renal disease.
- Peritoneal dialysis is often preferred in children due to simplicity and better hemodynamic tolerance.
- Haemodialysis is used in older children when facilities permit.
- Kidney transplantation offers the best long-term outcome, though access is limited in Ghana.

48.7.4 4. Psychosocial and Family Support

Chronic kidney disease imposes psychological and financial burdens. Family counselling, nutritional education, and social support are integral to management.

48.8 Complications

Untreated or poorly managed kidney disease can result in severe complications: - Hypertensive crisis
- Chronic kidney disease and end-stage renal failure
- Electrolyte disturbances (hyperkalaemia, hyponatraemia)
- Growth failure and bone disease
- Cardiovascular complications
- Infections from immunosuppression or dialysis
- Anaemia and fatigue

48.9 Prevention

Many causes of renal disease in children are preventable.

Key preventive measures include: - Antenatal care to detect congenital anomalies early.
- Prompt treatment of infections, particularly streptococcal throat and skin infections.
- Avoidance of nephrotoxic drugs (e.g., aminoglycosides, NSAIDs).
- Adequate hydration during diarrhoeal or febrile illnesses.
- Health education on hygiene and sanitation to prevent UTIs.
- Early referral for persistent oedema, hematuria, or hypertension.

48.10 Prognosis

The outcome varies with the cause and stage at diagnosis.
- Acute glomerulonephritis generally resolves completely with supportive care.
- Steroid-sensitive nephrotic syndrome has an excellent prognosis though relapses are common.
- Chronic kidney disease progresses slowly but inevitably to renal failure without intervention.
Early detection and multidisciplinary care significantly improve survival and quality of life.

48.11 Conclusion

The spectrum of kidney diseases in children is wide and complex, encompassing congenital, infectious, immune, and systemic disorders. In Ghana and similar settings, late presentation and limited diagnostic resources often worsen outcomes.

Medical students and young clinicians must develop a strong foundation in recognizing early signs, performing appropriate investigations, and instituting timely management. With better public health measures, increased awareness, and improved access to paediatric nephrology services, the burden of childhood renal disease can be significantly reduced.