Male infants under the age of 3 months presenting with pyelonephritis in the presence of urinary tract malformation (UTM) are prone to transient pseudohypoaldosteronism. This may resemble congenital adrenal hyperplasia (CAH). Hyponatremia, hyperkalemia, dehydration, and metabolic acidosis are the primary findings that permit the diagnosis of CAH. We report a case of transient pseudohypoaldosteronism resulting from pyelonephritis and vesicouretric reflux. The 17-day-old boy presented with a salt-losing episode simulating adrenal insufficiency. An initial diagnosis of CAH was made. The severe metabolic imbalance resulted in ventricular flutter that resolved after correction of the metabolic acidosis and the electrolyte and volume depletion. Early diagnosis is essential because both conditions are potentially fatal and treatment differs significantly. Differential diagnosis may be achieved by urinalysis and abdominal ultrasound scan.