Renal sonogram8/4/2023 Gray-scale sonography is initially used to assess the kidneys for any parenchymal or structural abnormality. The Doppler modalities are useful for evaluation of vascular structures. Duplex Doppler imaging provides a spectral trace recording frequency changes over time, reflecting the velocity profile. Color Doppler imaging superim- poses a color-coded velocity flow scale, based on the frequency shift of moving tissues, onto the gray- scale image. Gray-scale imaging depicts a structural rendition of the kidney based on acoustic interfaces (acoustic impedance differences between adjacent tissues). Sonographic evaluation of the kidneys is performed with a combination of gray-scale, color Doppler, and duplex Doppler imaging. Sonography is comparable with intravenous urography in the assessment of renal size and hydronephrosis, without the risks of intravenous contrast administration and patient exposure to ionizing radiation. Sonography has replaced the intravenous urogram as the initial imaging modality in the evaluation of infants and small children with hypertension. It is highly sensitive in detection of many of the parenchymal diseases of the kidney (see Box 1), and for evaluating anomalies of the renal collecting system. Renal sonography is typically used as the initial imaging modality in the evaluation of the hypertensive infant because of its convenience, accessibility, noninvasiveness, and lack of radiation exposure. Because most cases of infantile hypertension are caused by renal abnormalities, a diagnostic approach focused on the kidneys is vital. Most of the nonrenal causes can be suggested by the history, physical examination, and laboratory analysis. The nonrenal causes of infantile hypertension (see Box 1) constitute an array of conditions involving different organ systems including endocrine conditions, such as congenital adrenal hyperplasia pulmonary disorders, such as bronchopulmonary dysplasia and pneumothorax neoplastic entities, such as Wilms’ tumor and neuroblastoma neurologic conditions, such as intracranial hypertension and seizures and miscellaneous causes, such as total parenteral nutri- tion, hypercalcemia, adrenal hemorrhage, and medi- cations including dexamethasone, adrenergic agents, and others. Nonparen- chymal renal causes of hypertension include ureteropelvic junction obstruction vesicoureteral junction obstruction and renal obstruction from other causes, such as calculi, blood clots, or other mass lesion. Among renal parenchymal and cystic diseases potentially causing infantile hypertension are polycystic kidney disease (autosomal-recessive far more commonly than autosomal-dominant) unilateral renal hypoplasia congenital nephrotic syndrome and acquired conditions, such as acute tubular necrosis, acute cortical necrosis, and interstitial nephritis. As is discussed, however, angiography is less often performed in the evaluation of neonatal hypertension, most likely because of the technical difficulties and risks of anesthesia. Treatment also may be offered by angiography, because limited data in the older pediatric population have shown that percutaneous transluminal angioplasty can effectively treat renovascular hypertension.
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