BACKGROUND: Hyponatremic–hypertensive syndrome is a rare but distinctive manifestation of renal ischemia caused by unilateral renal artery stenosis. It is characterized by severe arterial hypertension accompanied by hyponatremia, hypokalemia, metabolic alkalosis, and polyuria, resulting from complex interactions between the ischemic kidney and the contralateral functioning kidney. Owing to its rarity and potentially life-threatening course, early recognition and appropriate management are crucial. The purpose of this report is to highlight the clinical presentation, diagnostic challenges, and therapeutic outcomes in pediatric patients.

CASE REPORT: We describe the cases of 2 girls, aged 4 and 9 years, who presented with severe hypertension and electrolyte disturbances secondary to unilateral right renal artery stenosis. Both patients exhibited typical biochemical features, including hyponatremia, hypokalemia, and elevated renin-aldosterone activity. Imaging studies confirmed significant unilateral renal artery stenosis due to fibromuscular dysplasia, with renal asymmetry. In the younger patient, progressive clinical deterioration and complete renal artery occlusion necessitated nephrectomy, resulting in resolution of hypertension and electrolyte abnormalities. In the older patient, percutaneous transluminal renal angioplasty was successful, leading to normalization of blood pressure, restoration of renal size symmetry, and sustained clinical remission at 1-year follow-up.

CONCLUSIONS: Hyponatremic–hypertensive syndrome should be considered in any child with severe hypertension accompanied by electrolyte disturbances, polyuria, and polydipsia. These 2 cases of girls with fibromuscular dysplasia underscore the importance of early recognition and individualized management strategies in pediatric renovascular hypertension. Prompt diagnosis and definitive treatment of renal artery stenosis, either by revascularization or nephrectomy when appropriate, can be curative and prevent severe morbidity. It is important to note that the course of HHS can vary among patients depending on their age, the severity, and the location of the stenosis.

Keywords: Fibromuscular Dysplasia, Hypertension, Hyponatremia, Renal Artery Obstruction, Renin-Angiotensin System