Question:
A 5-year-old child presents with failure to thrive, recurrent flank pain, and gross hematuria. Ultrasound shows nephrocalcinosis. Urine microscopy shows the following. Serum creatinine is elevated. What is the most likely diagnosis?
A 5-year-old child presents with failure to thrive, recurrent flank pain, and gross hematuria. Ultrasound shows nephrocalcinosis. Urine microscopy shows the following. Serum creatinine is elevated. What is the most likely diagnosis?
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Nephrocalcinosis in RTA Mechanism:
Metabolic Acidosis $\rightarrow \uparrow$ Bone reabsorption $\rightarrow$ Hypercalciuria + Hypocitraturia + Alkaline Urine ($\text{pH} > 5.5$) $\rightarrow$ Calcium Phosphate Precipitation in renal medulla.
Metabolic Acidosis $\rightarrow \uparrow$ Bone reabsorption $\rightarrow$ Hypercalciuria + Hypocitraturia + Alkaline Urine ($\text{pH} > 5.5$) $\rightarrow$ Calcium Phosphate Precipitation in renal medulla.
Updated On: Sep 3, 2026
- Cystinuria
- Hyperoxaluria
- Hypercalciuria
- Renal tubular acidosis
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The Correct Option is D
Solution and Explanation
Concept:
Nephrocalcinosis in pediatric patients refers to the generalized, diffuse deposition of calcium salts (calcium phosphate or calcium oxalate) within the renal parenchymal tissue, predominantly in the renal pyramids and medullary interstitium.
Distal Renal Tubular Acidosis (Type 1 RTA) is the classic tubulopathy leading to early, prominent medullary nephrocalcinosis, nephrolithiasis, and progressive renal insufficiency.
Explanation:
• In distal RTA (Type 1), failure of apical hydrogen ion pumps in the collecting duct causes persistent alkaline urine ($\text{Urine pH} > 5.5$) alongside systemic non-anion gap metabolic acidosis.
• Systemic metabolic acidosis stimulates continuous bone buffering, which leaches calcium and phosphate from skeletal stores into the bloodstream, producing marked hypercalciuria.
• Simultaneously, chronic acidosis markedly upregulates proximal tubular reabsorption of citrate, resulting in severe hypocitraturia (absence of citrate, the main endogenous inhibitor of calcium crystallization in urine).
• The combination of an alkaline urine pH, high urinary calcium concentration, and absent urinary citrate drives the rapid, massive precipitation of calcium phosphate (apatite) crystals in the renal tubules, producing medullary nephrocalcinosis.
• Over time, interstitial fibrosis and chronic nephrocalcinosis lead to renal scarring, recurrent hematuria, flank pain from calculi, failure to thrive, and elevated serum creatinine.
Final Answer:
The clinical triad of severe failure to thrive, nephrocalcinosis, and renal impairment is the hallmark presentation of distal Renal Tubular Acidosis (RTA).
Nephrocalcinosis in pediatric patients refers to the generalized, diffuse deposition of calcium salts (calcium phosphate or calcium oxalate) within the renal parenchymal tissue, predominantly in the renal pyramids and medullary interstitium.
Distal Renal Tubular Acidosis (Type 1 RTA) is the classic tubulopathy leading to early, prominent medullary nephrocalcinosis, nephrolithiasis, and progressive renal insufficiency.
Explanation:
• In distal RTA (Type 1), failure of apical hydrogen ion pumps in the collecting duct causes persistent alkaline urine ($\text{Urine pH} > 5.5$) alongside systemic non-anion gap metabolic acidosis.
• Systemic metabolic acidosis stimulates continuous bone buffering, which leaches calcium and phosphate from skeletal stores into the bloodstream, producing marked hypercalciuria.
• Simultaneously, chronic acidosis markedly upregulates proximal tubular reabsorption of citrate, resulting in severe hypocitraturia (absence of citrate, the main endogenous inhibitor of calcium crystallization in urine).
• The combination of an alkaline urine pH, high urinary calcium concentration, and absent urinary citrate drives the rapid, massive precipitation of calcium phosphate (apatite) crystals in the renal tubules, producing medullary nephrocalcinosis.
• Over time, interstitial fibrosis and chronic nephrocalcinosis lead to renal scarring, recurrent hematuria, flank pain from calculi, failure to thrive, and elevated serum creatinine.
Final Answer:
The clinical triad of severe failure to thrive, nephrocalcinosis, and renal impairment is the hallmark presentation of distal Renal Tubular Acidosis (RTA).
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