Renal calcification in children with renal tubular acidosis: What a paediatrician ‎should ‎know‎

Table 3 Comparison of clinical and laboratory data between type 1 and type 2 renal tubular acidosis

Feature		Type 1 RTA	Type 2 RTA
Prevalence		More common than type 2 RTA	Less common than type 1 RTA
Cause		Usually isolated, inherited, autosomal recessive forms are associated with hearing loss	Usually secondary to a systemic disease, most often metabolic disease, e.g., Fanconi syndrome
Clinical features	Nephrocalcinosis	Often present	Occasionally present
	Polyuria (increased urine output)	Common	Common
	Polydipsia (increased thirst)	Common	Common
	Dehydration	Less common	Less common
	Bone abnormalities	Usually, severe	Variable
	Failure to thrive (children)	Occasional	Uncommon
	Rickets/osteomalacia (children)	Occasional	Uncommon
	Metabolic acidosis	Severe acidosis; is easily corrected with bicarbonate supplementation	Usually milder but difficult to correct; requires high doses of bicarbonate supplementation
Laboratory Finding	Serum HCO3- (bicarbonate)	Decreased	Decreased
	Serum potassium	Low	Normal/low
	Urine pH	> 5.5	< 5.5
	Fractional excretion of bicarbonate	< 5%	> 15%
	Urine-blood PCO2	< 20 mmHg	> 20 mmHg
	Phosphaturia and hypophosphatemia	Absent	Present (variable)
	Tubular defects – low-molecular-weight proteinuria, aminoaciduria, glycosuria	Absent	Present (variable)
	Hypercalciuria	Often present	Occasionally present

RTA: Renal tubular acidosis.