The most common cause of renovascular hypertension in the newborn is which of the following?

• A. Umbilical artery catheterization
• B. Congenital renal artery stenosis
• C. Umbilical venous catheterization
• D. Neonatal polycythemia

Answer: (A)

Renovascular hypertension in the newborn most often results from injury to the renal arteries due to umbilical artery catheterization. The catheter can cause thrombosis or embolization in the renal arteries, leading to renal ischemia. When the kidney experiences ischemia, the juxtaglomerular cells release renin, activating the renin-angiotensin-aldosterone system and increasing systemic blood pressure. While congenital renal artery stenosis can cause similar problems, it is much less common in the neonatal period. Umbilical venous catheterization primarily affects the venous system and is not a typical cause of renovascular hypertension, and polycythemia raises blood pressure through hyperviscosity rather than renovascular mechanisms.