Pediatric hospitalists consider that the association between acute pyelonephritis and temporary poor responsiveness to aldosterone is very uncommon and feel comfortable with this diagnosis exclusively if the diagnostic work-up also includes the assessment of urinary electrolytes and even laborious tests such as renin, aldosterone, cortisol and 17-hydroxyprogesteron, whose laboratory turnaround time is generally several days [2, 3, 9]. The gene discussed is REN; the disease is acute pyelonephritis.