Since the majority of hypertension in the pediatric population is “renal related”, nephrology is commonly the first subspecialty contacted, unless another cause is immediately obvious. However, the initial work-up and initiation of treatment may be accomplished by the PCP in asymptomatic, uncomplicated cases, with non-emergent levels of blood pressure.
Early testing includes 4 extremity blood pressures looking for aortic coarctation (lower pressures than in the legs), serum BUN, creatinine, electrolytes, and urinalysis (UA). Abnormal renal function and/or UA suggesting renal disease should prompt earlier rather than later nephrology referral. Renal ultrasound with Doppler flow study is also part of the initial work-up and is obtained to rule out abnormalities of the renal parenchyma, urinary tract abnormalities such as hydronephrosis suggesting either reflux or obstruction, and to demonstrate renal blood flow irregularities suggesting renal artery stenosis (RAS). A renal MRA is felt to be more sensitive in revealing RAS, and if that is demonstrated referral to an interventional radiologist is recommended [Note: transluminal angioplasty of the stenosis may not be possible in the very small child in which case a surgical approach would be taken].
Abnormalities of the urinary tract indicate urology referral to address the abnormality, but nephrology should remain involved with the hypertension treatment.
Electrolyte abnormalities supporting hyperadrenalism (hypokalemic alkalosis) should also be referred either to nephrology or endocrinology (as should cases of hyperthyroidism or hypercalcemia and hypertension, e.g.). Coarctation of the aorta, although not considered a renal problem, results in hypertension through under perfusion of the kidneys. This abnormality should also be ruled out in the initial evaluation by the PCP. Its presence may be discernible by lower blood pressure (and at times notably decreased pulses) in the legs compared to the arms [Note: Leg pressure is normally higher than arm pressure]. Cardiac ECHO will be definitive in ruling this out. If present, referral to cardiovascular surgery is indicated.
Obtaining urine VMA is also part of the initial work-up, although cases of pheochromocytoma are rare. If suspected, serum catecholamines are measured and CT of thorax and abdomen are warranted with referral to oncology/surgery if a lesion is found.
Treatment of hypertension should be initiated while the work-up is in progress. Drug choices should be discussed with a nephrologist. If no etiology is found, the consideration of so-called “essential” (arguably more properly called “primary”) hypertension is valid, with continued follow up and treatment control of blood pressure. This can be done either by the PCP with nephrology guidance or, if preferred, by nephrology.
Hypertension in the newborn period generally prompts at least a discussion with nephrology [Note: 80% of secondary hypertension in infants is transient and may be related to bronchopulmonary dysplasia (BPD), medications, volume excess, etc—the remaining percentage includes renovascular abnormalities, coarctation of the aorta, obstructive uropathy, and autosomal recessive polycystic kidney disease]. When no obvious etiology can be found and addressed, treatment is begun regardless, and is expected to be limited. Specific follow up by Nephrology is not absolutely necessary in settings where the treatment is not complicated and control of blood pressure is easily obtained, as our nephrologists are available for “curbside” discussions.
