Eosinophilic cystitis-an obscure case of obstructive uropathy in infancy

We report on an infant with features of intermittent obstructive uropathy, acute kidney injury, hypertension and type 4 renal tubular acidosis (RTA) despite urethral catheterisation and fluid resuscitation. Radiological findings showed upper tract dilatation, likely bilateral vesicoureteric junction obstruction and bladder base thickening which was concerning for possible malignancy. Renal biopsy demonstrated eosinophilic infiltrate, suggestive of kidney involvement. Bladder biopsy was diagnostic for eosinophilic cystitis (EC) showing mature degranulating eosinophils. EC is a rare, easily treatable and important differential of bladder mass in children which may present with an atypical obstructive uropathy. This report adds to the limited literature of this condition within the paediatric population. EC should be considered early in children presenting with eosinophilia, urinary tract obstruction and kidney dysfunction, with uncertain aetiology. This case also highlights the need for detailed imaging, including visualisation of the bladder base, in cases of likely obstructive uropathy.