Overview
Definition:
Nephrolithiasis in children refers to the formation of solid mineral deposits (stones) within the kidney or urinary tract
It is a significant clinical problem with increasing incidence in pediatric populations, often associated with underlying metabolic abnormalities
Early diagnosis and appropriate metabolic evaluation are crucial to prevent recurrence and long-term renal damage.
Epidemiology:
The incidence of pediatric nephrolithiasis is rising globally
It affects approximately 0.05% to 0.1% of children
There is a bimodal age distribution, with peaks in infancy and early childhood, and then again in adolescence
Boys are more commonly affected than girls, though this can vary with stone composition and age
Recurrence rates are high, often exceeding 50% within 5 years without adequate management.
Clinical Significance:
Pediatric nephrolithiasis is important due to the potential for severe pain, urinary tract infections, obstruction, renal damage, and chronic kidney disease
Unlike adults, children have a longer lifespan ahead, making the long-term consequences of recurrent stones and impaired renal function more profound
Identifying and treating underlying metabolic disorders is paramount to preventing recurrence and preserving renal health throughout their lives.
Clinical Presentation
Symptoms:
Hematuria, which can be gross or microscopic
Flank pain or abdominal pain, often colicky, radiating to the groin
Nausea and vomiting
Urinary tract infection symptoms such as dysuria, frequency, urgency, and fever
Failure to thrive or irritability in infants
Asymptomatic presentation detected incidentally on imaging.
Signs:
Tenderness in the costovertebral angle (flank tenderness)
Abdominal distension
Fever and signs of sepsis if an infection is present
Irritability or poor feeding in infants
Dehydration.
Diagnostic Criteria:
Diagnosis is typically confirmed by imaging modalities
Clinical suspicion, supported by positive findings on urinalysis (hematuria, crystalluria) and confirmed by imaging (ultrasound, CT scan, KUB X-ray), forms the basis for diagnosis
Identification of an underlying metabolic abnormality guides further management and prevention.
Diagnostic Approach
History Taking:
Detailed family history of kidney stones, metabolic disorders, or renal disease
Dietary habits (high salt, high protein, low fluid intake)
History of recurrent urinary tract infections
Previous episodes of stone passage or flank pain
Medication history, including vitamin and herbal supplements
History of malabsorption or gastrointestinal surgery
Birth history and perinatal complications.
Physical Examination:
General examination including growth parameters (height, weight, BMI)
Abdominal examination for tenderness, masses, or distension
Palpation of the costovertebral angle
Examination of external genitalia and for signs of urinary tract infection
Assessment for signs of rickets or bone abnormalities if calcium-phosphorus metabolism is suspected.
Investigations:
Urinalysis: pH, specific gravity, presence of red blood cells, white blood cells, crystals (e.g., calcium oxalate, uric acid, cystine), and protein
Urine culture and sensitivity
24-hour urine collection for volume, pH, calcium, oxalate, citrate, uric acid, sodium, creatinine, and cystine
Serum biochemistry: electrolytes, BUN, creatinine, calcium, phosphorus, uric acid, albumin
Serum electrolytes, calcium, phosphorus, uric acid, and renal function tests are essential
For suspected cystinuria, plasma amino acid levels may be useful
Imaging: Renal ultrasound is usually the initial imaging modality of choice due to its safety and efficacy in detecting stones
Non-contrast CT scan of the abdomen and pelvis is highly sensitive for stone detection and localization
KUB X-ray may be used for radiopaque stones.
Differential Diagnosis:
Urinary tract infection
Pyelonephritis
Appendicitis
Ovarian or testicular torsion
Musculoskeletal pain
Intussusception
Renal tumor
Renal vein thrombosis
Hydronephrosis of other etiologies.
Metabolic Workup
Indications For Metabolic Evaluation:
All children with nephrolithiasis should undergo metabolic evaluation to identify underlying causes and guide preventive strategies
This is particularly important in recurrent stone formers and those with a family history of stones or metabolic disorders
Infants and very young children are also at higher risk for metabolic causes.
Urine Metabolic Evaluation:
24-hour urine collection is the cornerstone
Key parameters include: Urine volume (low volume increases supersaturation)
Urinary pH (alkaline urine favors calcium phosphate stones
acidic urine favors uric acid and cystine stones)
Urinary Calcium (hypercalciuria: absorptive, resorptive, renal leak)
Urinary Oxalate (hyperoxaluria: primary or secondary due to malabsorption)
Urinary Citrate (hypocitraturia is a major risk factor for calcium-based stones)
Urinary Uric Acid (hyperuricosuria)
Urinary Cystine (for cystinuria)
Sodium excretion (high sodium intake can increase urinary calcium excretion).
Serum Metabolic Evaluation:
Serum calcium and phosphorus levels (to rule out hyperparathyroidism or renal tubular acidosis)
Serum uric acid levels (to identify hyperuricemia)
Serum bicarbonate and electrolytes (to assess for distal renal tubular acidosis)
Vitamin D levels, parathyroid hormone (PTH) if hypercalcemia is present.
Identifying Common Metabolic Disorders:
Hypercalciuria (idiopathic, renal tubular acidosis, hyperparathyroidism, immobilization)
Hyperoxaluria (primary, enteric)
Hypocitraturia (idiopathic, distal RTA, chronic diarrhea)
Hyperuricosuria (high purine diet, certain genetic disorders)
Cystinuria (genetic defect in amino acid transport)
Uric acid stones (dehydration, high purine diet, enzymatic defects).
Management
Initial Management:
Pain control with analgesics (NSAIDs are effective)
Hydration: encouraging oral fluid intake, or intravenous fluids if vomiting or unable to tolerate oral intake
Medical expulsive therapy (e.g., alpha-blockers) may be considered for smaller stones
Antibiotics if concurrent infection is present.
Medical Management:
For calcium stones: Thiazide diuretics (e.g., hydrochlorothiazide) for hypercalciuria
Potassium citrate supplementation for hypocitraturia and to increase urine pH
Allopurinol for hyperuricosuria
For uric acid stones: alkalinization of urine with potassium citrate
Low purine diet
For cystine stones: aggressive hydration and urine alkalinization with potassium citrate
Captopril or tiopronin may be considered in severe cases
Dietary modifications are crucial for all types of stones.
Surgical Management:
Indications for intervention include: severe pain unresponsive to medical management, infection, obstruction, stone burden greater than 5mm in children with risk of obstruction, solitary kidney, or significant progression of hydronephrosis
Options include: Extracorporeal shock wave lithotripsy (ESWL), Ureteroscopy with laser lithotripsy, Percutaneous nephrolithotomy (PCNL), Open stone surgery (rarely indicated in children).
Supportive Care:
Nutritional counseling: adequate fluid intake (aiming for dilute urine), balanced diet, reducing sodium and animal protein intake
Regular monitoring of renal function and stone burden
Education on recurrence prevention and lifestyle modifications.
Complications
Early Complications:
Acute renal failure due to obstruction or infection
Sepsis
Hemorrhage
Injury to adjacent organs during procedures.
Late Complications:
Chronic kidney disease
Recurrent urinary tract infections
Hypertension
Growth retardation
Infertility
Recurrent stone formation leading to progressive renal damage.
Prevention Strategies:
Aggressive hydration (aiming for urine output > 2-3 mL/kg/hr or specific gravity < 1.010)
Dietary modifications based on metabolic evaluation (e.g., reduced sodium, animal protein, oxalate)
Pharmacological therapy tailored to specific metabolic derangements (e.g., thiazides, potassium citrate)
Regular follow-up with urine and serum monitoring.
Prognosis
Factors Affecting Prognosis:
The presence of an underlying metabolic disorder
Promptness and adequacy of diagnosis and treatment
Adherence to preventive measures and lifestyle modifications
The size, number, and location of stones
The presence of obstruction and infection
Underlying renal function at diagnosis.
Outcomes:
With appropriate metabolic workup and management, the majority of children with nephrolithiasis can achieve stone-free status and significantly reduce their risk of recurrence
However, some may develop chronic kidney disease or require repeated interventions, especially if the underlying metabolic cause is severe or poorly managed.
Follow Up:
Long-term follow-up is essential
This typically involves regular (e.g., every 6-12 months initially) assessment of renal function, urine chemistry, and imaging to detect any new stone formation or complications
Adherence to preventive strategies is crucial for long-term success.
Key Points
Exam Focus:
Recognize that children with nephrolithiasis often have an underlying metabolic abnormality
The 24-hour urine collection is the cornerstone of metabolic evaluation
Key parameters to remember are urine volume, pH, calcium, oxalate, citrate, and uric acid
Hypocitraturia and hypercalciuria are common
Thiazides and potassium citrate are important pharmacologic agents
DNB/NEET SS questions often test the approach to metabolic workup and specific management strategies for different stone types.
Clinical Pearls:
Always consider nephrolithiasis in children presenting with unexplained flank pain, hematuria, or recurrent UTIs
Aggressive hydration is the first-line preventive measure
In infants, metabolic causes are more likely and presentation can be subtle (irritability, poor feeding)
Don't forget to assess family history of stones or metabolic bone disease
Ensure accurate collection of 24-hour urine samples
patient/parent education is key.
Common Mistakes:
Failing to perform a comprehensive metabolic workup in all pediatric stone formers
Incorrect interpretation of 24-hour urine results
Inadequate fluid intake recommendations
Over-reliance on imaging without considering the underlying metabolic cause
Delaying intervention for symptomatic or obstructing stones
Not tailoring dietary and pharmacological advice to specific metabolic derangements.