Published in:
01-12-2011 | Clinical Quiz
Failure to thrive and nephrolithiasis in a boy with congenital cyanotic heart anomaly: answers
Published in: Pediatric Nephrology | Issue 12/2011
Login to get accessExcerpt
1.
Distal (Type I) renal tubular acidosis (RTA).
This child had biochemical evidence of hyperchloremic metabolic acidosis with a normal serum anion gap ([Na+]+[K+] ) − ( [Cl−] + [HCO 3 − ] ). Simultaneous to blood chemistry, urinalysis revealed pH of 7.17, indicating a distal tubular acidification defect. The urinary anion gap [Na+]+[K+] − [Cl−] was positive at 39 mmol/l, suggesting a low urinary NH 4 + in favor of RTA.
2.
Cyanotic heart anomaly leads to a respiratory metabolic acidosis (due to retained CO2) and failure to thrive. Successful repair of the heart anomaly should result in prompt resolution of cyanosis and metabolic acidosis (within 48 h) [1]. Persistence of metabolic acidosis beyond this period and continued failure to thrive should alert the clinician to an alternative (extra-cardiorespiratory) cause, such as a renal tubular acidification defect, as in this case.
3.
The findings of low molecular weight proteinuria, aminoaciduria, phosphaturia, and uricosuria alongside metabolic acidosis may lead to confusion with renal Fanconi syndrome. These proximal tubular abnormalities were transitory and resolved with alkali therapy. Transitory proximal renal tubular dysfunction may be associated with distal RTA [2‐4].