✅ Model Answer:
• Diagnosis: Idiopathic hypercalciuria – excessive urinary calcium excretion with normal serum calcium.
• Evidence: Recurrent gross hematuria, spot urine Ca:Cr >0.2 (0.3), normal serum calcium, normal renal ultrasound, no proteinuria.
• Next step: High fluid intake (2-3 L/day), low sodium diet (<2 g/day), normal calcium intake (DO NOT restrict). Monitor urine Ca:Cr every 3-6 months. If persistent symptoms, consider hydrochlorothiazide 1-2 mg/kg/day.

✅ Model Answer:
• Idiopathic hypercalciuria: Increased urinary calcium excretion (>4 mg/kg/day or Ca:Cr >0.2) with normal serum calcium, in the absence of secondary causes (hyperparathyroidism, vitamin D excess, immobilization, sarcoidosis, etc.).
• Subtypes:
- Absorptive hypercalciuria: Increased intestinal calcium absorption (most common). PTH is normal or low.
- Renal hypercalciuria: Impaired renal calcium reabsorption (PTH is elevated as compensation).
- Resorptive hypercalciuria: Increased bone resorption (rare, usually with hyperparathyroidism).
- Dietary hypercalciuria: Excessive calcium or sodium intake.
• Prevalence: Affects 3-5% of children; most common cause of hematuria in children.

✅ Model Answer:
• Renal symptoms:
- Gross hematuria: Recurrent, painless or with dysuria (most common presentation).
- Microscopic hematuria: Asymptomatic (incidental).
- Dysuria, urgency, frequency.
- Abdominal pain: Flank or suprapubic pain.
- Nephrolithiasis: Calcium oxalate or calcium phosphate stones.
- Nephrocalcinosis: Renal calcification (in severe cases).
• Other features:
- Family history: Hypercalciuria or nephrolithiasis in 30-50% of cases.
- Often asymptomatic (discovered incidentally).
- Enuresis: Nocturnal enuresis in some children (due to polyuria).

✅ Model Answer:
• Urine studies:
- Spot urine calcium/creatinine ratio: >0.2 (children) or >0.6 (older children/adults) is suggestive.
- 24-hour urine calcium: >4 mg/kg/day confirms diagnosis.
- Urinalysis: Microscopic hematuria, no proteinuria, no RBC casts (differentiates from glomerular disease).
• Serum studies:
- Calcium, phosphorus, PTH, 25-OH vitamin D: To rule out secondary causes (hyperparathyroidism, vitamin D excess).
- Electrolytes, renal function (creatinine, BUN).
• Imaging:
- Renal ultrasound: To rule out nephrocalcinosis or stones.
- KUB X-ray or CT: If stones are suspected.
• Family history: Screen family members for hypercalciuria.

✅ Model Answer:
• First-line (conservative):
- High fluid intake: 2-3 L/day (urine output >1.5 L/day).
- Low sodium diet: <2 g/day (sodium increases calcium excretion).
- Normal calcium intake: DO NOT restrict calcium (restriction increases stone risk).
- Low oxalate diet: If oxalate stones (avoid spinach, nuts, chocolate).
- Avoid: Vitamin D supplements, calcium supplements (unless deficient).
• Medical therapy (if conservative fails):
- Hydrochlorothiazide: 1-2 mg/kg/day (increases renal calcium reabsorption).
- Potassium citrate: For hypocitraturia (if stones).
- Amiloride: Alternative thiazide.
• Indications for treatment: Recurrent stones, persistent gross hematuria, nephrocalcinosis, or severe symptoms.

✅ Model Answer:
• Renal complications:
- Nephrolithiasis: Calcium oxalate or calcium phosphate stones → obstruction, infection, pain.
- Nephrocalcinosis: Calcium deposition in renal tubules → chronic kidney disease (rare).
- Recurrent urinary tract infections: Due to stones.
- Hematuria: Gross or microscopic (can cause anxiety).
- Chronic kidney disease: In severe, long-standing cases.
• Other:
- Bone pain: In severe cases (rare).
- Growth failure: If chronic disease.
- Psychosocial impact: From recurrent symptoms and hospitalizations.

✅ Model Answer:
• Prognosis:
- Good with conservative management (hydration, low sodium).
- Spontaneous resolution: Some children outgrow it.
- Recurrence: High risk of recurrence if not treated.
- Risk of stones: 10-15% lifetime risk of nephrolithiasis.
- Renal function: Usually normal if no nephrocalcinosis.
• Long-term follow-up:
- Monitor urine Ca:Cr: Every 3-6 months.
- Renal ultrasound: Annually to check for nephrocalcinosis or stones.
- Blood pressure monitoring.
- Educate: Hydration, diet, and early recognition of stones.
- Family screening: If family history of nephrolithiasis.

✅ Model Answer:
• Hydrochlorothiazide: A thiazide diuretic that reduces urinary calcium excretion.
• Mechanism:
- Inhibits sodium-chloride cotransporter in the distal convoluted tubule → increases sodium excretion → reduces calcium excretion (due to volume contraction and increased proximal calcium reabsorption).
- Result: Decreased urinary calcium concentration → reduced stone formation.
• Indications:
- Recurrent nephrolithiasis.
- Persistent gross hematuria.
- Nephrocalcinosis.
- Failure of conservative therapy.
• Dose: 1-2 mg/kg/day (usually 25-50 mg/day in older children).
• Side effects:
- Hypokalemia (monitor potassium).
- Hypercalcemia (rare).
- Hypovolemia, dizziness.
- Hyperglycemia (monitor glucose).
• Monitoring: Electrolytes, calcium, renal function, urine calcium.