Neonatal urinary ascites is a rare entity, usually associated with a spontaneous rupture of the bladder with an underlying pathology such as high pressure or wall disruption. Its presentation involves abdominal distension, metabolic derangement and respiratory compromise. We report the case of a male neonate with solitary functioning kidney presented with life-threatening persistent hyponatremia and acute renal failure due to iatrogenic bladder rupture after catheterization. The aim of our report is to raise awareness on the possibility of bladder perforation in neonates even in the absence of technical faults. We discuss the uncommon presentation of our case and highlight the need for early recognition and management of urinary ascites, addressing all subspecialties involved in diagnostic or therapeutic procedures of neonates with urinary abnormalities.