From the Guidelines
The differential diagnoses for an infant with medullary nephrocalcinosis, weight loss, and vomiting should focus on metabolic disorders, particularly distal renal tubular acidosis (dRTA), Bartter syndrome, and primary hyperoxaluria. Initial workup should include:
- Comprehensive metabolic panel
- Urinalysis
- Urine calcium-to-creatinine ratio
- Urine pH
- Serum electrolytes
- Blood gas analysis
- Renal ultrasound For dRTA, look for metabolic acidosis with normal anion gap, alkaline urine, hypokalemia, and hypercalciuria 1. Bartter syndrome presents with hypokalemic metabolic alkalosis, hypercalciuria, and normal blood pressure 1. Primary hyperoxaluria shows elevated urinary oxalate levels. Management depends on the specific diagnosis but generally includes fluid rehydration, electrolyte correction, and acid-base balance restoration. For dRTA, alkali therapy with sodium bicarbonate or potassium citrate (1-3 mEq/kg/day divided into 3-4 doses) is indicated. Bartter syndrome requires potassium supplementation, NSAIDs like indomethacin (1-3 mg/kg/day), and sometimes potassium-sparing diuretics 1. Primary hyperoxaluria management includes high fluid intake, pyridoxine supplementation, and dietary oxalate restriction. Prompt diagnosis is crucial as these conditions can lead to failure to thrive, dehydration, and progressive renal damage if left untreated. It is also important to consider other potential causes of vomiting in infants, such as gastrointestinal obstruction, infections, and metabolic disorders, and to perform a thorough clinical evaluation, including history and physical examination, to guide the diagnostic workup 1.
From the Research
Differential Diagnoses
The differential diagnoses for an infant presenting with medullary nephrocalcinosis, significant weight loss, and vomiting include:
- Hereditary tubular disorders, such as distal renal tubular acidosis and Dent disease 2
- Metabolic disorders, including idiopathic hypercalciuria and hyperoxaluria 2, 3
- Iatrogenic causes, such as vitamin D intoxication 2
- Primary hyperoxaluria, which can lead to early onset nephrocalcinosis and chronic kidney disease 2, 3
- Syndrome of apparent mineralocorticoid excess type 1, characterized by hypokalaemia, metabolic alkalosis, and increased urinary potassium excretion 4
- Bartter syndrome, which can be associated with hypercalciuria and nephrocalcinosis 5
Initial Workup
The initial workup for an infant presenting with these symptoms should include:
- Family history and clinical context to guide further investigation 2, 3
- Complete laboratory data, including serum electrolytes, urine analysis, and blood biochemistry 2, 3
- Imaging studies, such as sonography, to detect echo-enhanced structures in the renal medulla region 6
- Screening tests for inherited diseases, such as idiopathic hypercalciuria, renal hypophosphatemia, and renal tubular acidosis 3
- Genetic testing, including next-generation sequencing, to diagnose rare diseases 3
- Investigation of vitamin D metabolism and calcium excretion to rule out absorptive hypercalciuria 5