Unilateral renal ischemia causing the hyponatremic hypertensive syndrome in children—more common than we think?

A case report in the journal Pediatric Nephrology describes a 15-month-old girl with the syndrome of hypertension and hyponatremia (HH syndrome) due to underlying unilateral renal artery stenosis. This syndrome is typically associated with hypokalemia and severe volume depletion and sometimes proteinuria, all of which, along with hypertension and hyponatremia, are usually corrected by resolution of the underlying renal ischemia. Gross and probably sudden activation of the renin-angiotensin system in response to renal ischemia is central to the pathophysiology although the cardiac atrial and B-type natriuretic peptides probably contribute also. Initial control of the severe hypertension may, in some cases, require careful volume repletion prior to introduction of blockade of the renin–angiotensin system in order to avoid first-dose hypotension, after which correction of the underlying renal ischemia is required. Whereas the syndrome has rarely been reported in children, it is possible that, as in adults, this reflects its lack of recognition by clinicians. The HH syndrome due to unilateral renal ischemia in children may be much more common than we think.