NEONATAL HYPERTENSION LAB STUDIES

Lab Studies:
• Usually only a limited set of laboratory data is needed in the evaluation of neonatal hypertension. Obtain serum electrolytes, creatinine, BUN, and a urinalysis in order to look for renal parenchymal disease. Obtain endocrinologic studies, such as cortisol, aldosterone, or thyroxine, when pertinent history exists.

• Measurement of plasma renin activity is usually recommended as part of the laboratory assessment of hypertensive newborns, although an elevated peripheral renin may not signify the presence of underlying pathology because renin values are typically quite high in infancy. In addition, plasma renin may be elevated falsely by medications that are commonly used in the NICU, such as aminophylline. Keep these factors in mind when interpreting renin values.

Imaging Studies:
• Chest radiography may be helpful in infants with CHF or in those with a murmur on physical examination.

• Obtain renal ultrasonography in all hypertensive infants. Accurate renal ultrasonography may help uncover potentially correctable causes of hypertension (eg, RVT); it may detect aortic thrombi, renal arterial thrombi, or both; and it can reveal anatomic renal abnormalities or other congenital renal parenchymal disease.

Ultrasonography is fast, noninvasive, and relatively inexpensive. Ultrasonography has largely replaced intravenous pyelography, which has little, if any, use in the routine assessment of neonatal hypertension.

• For infants with extremely severe BP elevation, angiography may be necessary. Although some investigators have used aortography via the umbilical artery catheter, a formal angiography using the traditional femoral venous approach is much more accurate for diagnosing renal arterial stenosis, primarily because of the high incidence of intrarenal branch vessel abnormalities observed in children with FMD.

• Nuclear scanning may demonstrate abnormalities of renal perfusion caused by thromboembolic phenomenon, although obtaining good studies in infants is difficult because of their immature renal function.

• Obtain other studies, including echocardiography and voiding cystourethrography, as indicated.